to it - Imem-Cnr

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to it - Imem-Cnr

ABSTRACTS BOOK
5th European Conference on Crystal Growth
9-11 September 2015
Area della Ricerca CNR, Bologna, Italy
WELCOME
Dear Colleagues,
On behalf of the Crystal Growth section of Italian Association of Crystallography (AIC) and the European
Network of Crystal Growth (ENCG), we cordially welcome you to Bologna for the Fifth European Conference
on Crystal Growth (ECCG5).
The aim of ECCG5 is to represent the wide variety of topics connected with Crystal Growth, with a
multidisciplinary approach able to answer the demands of the society in different fields of modern life, such as
microelectronics, photonics, pharmaceutical and chemical material production, healthcare and cosmetics to
name few. To delivery this, the organizing team has scheduled a wide-ranging and thought-provoking program
of Plenary, Keynote and Invited conference lectures. The conference also presents two poster sessions,
which are rich of very attractive and stimulating presentations.
The Conference has been also organized to promote the meeting of researchers coming from public and
private entities and to facilitate the cooperation between academia and industry. We aspect that that the
program will trigger many fruitful discussions and that this will be an enriching experience for all of us.
We express our heartfelt gratitude to the members of International Advisory Board for their qualified and wise
guidance concerning the conference structure, content and speakers and to the Local Organizing Committee
who have worked in very hard way to make easy many practical, and unexpected, issues associated with the
conference organization. Last but not least we are very grateful to the Sponsors and Exhibitors for their
significant support.
Once again we would like to thank all of you for the participation. We are honored to have all you in Bologna
and we wish you an inspiring, stimulating and enjoyable meeting.
BENVENUTI!
Giuseppe Falini
Andrea Zappettini
CONTENTS
Organisation
Page 3
Scientific Program Arrangements
Page 9
Poster Sessions
Page 10
Prizes
Page 11
Plenary Lectures
Page 12
Meeting Timetable
Page 13
Poster Presentations
Page 22
ABSTRACTS
Session 1
Keynotes and oral in order of presentation
Posters
Page 34
Page 44
Session 2
Posters
Page 66
Page 81
Session 3
Posters
Page 110
Page 118
Session 4
Posters
Page 122
Page 139
Session 5
Page 185
Posters
Page 193
Session 6
Posters
Page 201
Page 209
Session 7
Posters
Page 214
Page 222
Session 8
Posters
Page 234
Page 249
Session 9
Posters
Page 268
Page 277
Session 10
Posters
Page 296
Page 306
Session 11
Posters
Page 331
Page 339
ORGANISATION
Conference Chairs
Giuseppe Falini, Università di Bologna
Andrea Zappettini, IMEM-CNR, Parma
International Advisory Board
Horia Alexandru
Knut Deppert
Thierry Duffar
Francois Dupret
Roberto Fornari
Christiane Frank-Rotsch
Katharina Fromm
Brian Glennon
Jaime Gómez-Morales
Zdenek Kozisek
Damir Kralj
Harri Lipsanen
Hans Erik Lundager Madsen
Florinda Mendes da Costa
Wolfram Miller
Jozef Novak
Eivind Øvrelid
Katalin Polgar
Stathis Polychroniadis
Vyacheslav Puzikov
Bogdan Ranguelov
Kevin Roberts
Ewa Talik
Janis Virbulis
Daniel Vizman
Elias Vlieg
Evgeny Zharikov
Scientific Committee
Liliana Braescu
Thierry Duffar
Giuseppe Falini
Christiane Frank-Rotsch
Peter Gille
Jaime Gómez-Morales
Damir Kralj
Harri Lipsanen
Hans Erik Lundager Madsen
Florinda Mendes da Costa
Josef Novak
Carlos M. Pina
Bogdan Ranguelov
Kevin Roberts
Luca Seravalli
Ewa Talik
Alexander van Driessche
Janis Virbulis
Andrea Zappettini
Evgeny Zharikov
Organizing Committee
Davide Calestani
Matteo Di Giosia
Simona Fermani
Simona Galli
Annalisa Guerri
Patrizia Rossi
Conference Secretariat (@IMEM-CNR)
Rosella Magno
Antonella Secondulfo
[email protected]
Congress Venue
ECCG5 Conference will be hosted by CNR Bologna Research Area, Via Gobetti 101, Bologna.
The Area offers services and support to the Italian National Research Council (CNR) and the National Institute
for Astrophysics (INAF) Institutes present on the site as well as to those in other cities in Emilia-Romagna. On
the campus in Via Gobetti there are a total of eight Institutes belonging both to the CNR and INAF, together
with the central Area Library, Conference Centre and ancillary services. The site also accommodates ASTER
(regional government science and technology agency), various groups working within the framework of
SPINNER projects (promoting innovation and research) and laboratories MIST E-R and PROAMBIENTE, for
industrial research and technology transfer.
The Conference Centre
The striking design of the CNR Conference
Centre is the work of Enzo Zacchiroli, one of
Italy's most famous architects for public
building projects. The complex is an integral
part of the Research Area campus, and was
specifically designed for scientific discussion,
meetings and conferences. It boasts a high
degree of functionality within an attractive and sympathetic academic environment.
How to get there
If you arrive by car (from the motorway):
take the Bologna Arcoveggio exit, follow the
instructions for Via Gobetti, then follow the MAP
because the navigation systems may lead you
astray.
If you arrive by car (from the ring road "Tangenziale"):
take exit n. 5 (LAME), follow the instructions for Via
Gobetti, then follow the MAP because the
navigation systems may lead you astray.
If you arrive by train:
the CNR is a 5-minute taxi journey from "Bologna
Centrale" Railway Station: ask for "CNR, via Gobetti
101".
You can also arrive by bus, see below.
If you arrive by plane:
take the AEROBUS BLQ and change to the 87 bus at the "Ospedale Maggiore" bus stop, or take a taxi: the
CNR is a 10-minute taxi ride (ask for "CNR, via Gobetti 101").
If you arrive by bus:
Bus n. 87
From
Autostazione
Rotonda CNR 12 minutes
to
Timetables and details bus 87
Internet Facilities
WiFi will be available.
Bus n. 11A
Bus n. 11C
From
Autostazione
to
Rotonda Gobetti 18 + 8
minutes by walk
From Autostazione to Palestra
Ippodromo 17 minutes + 7
minutes by walk
Timetables and details bus 11
Conference Maps
Main Lecture Theatre – Room 105
Room 215
Registration Desk
It will be open on Tuesday 8th September from 17:00 followed by the Welcome Cocktail at the “Auditorium
Enzo Biagi – Salaborsa” in Piazza del Nettuno 3, Bologna.
The registration desk, throughout the congress, will be located on Ground Floor of the Conference Centre.
Conference Fees
On-site will be available. Payments can also be done by bank transfer or paypal.
The registration fee includes:
- welcome party
- access to the conference hall
- conference materials
- coffee breaks and launches
- certificate of attendance.
All participants will receive a name badge when they check in at the registration desk.
This badge must be worn at all times because only registered people will be accepted in conference halls and
in the catering area.
Welcome party
Welcome Cocktail will take place at 18.00 at the “Auditorium Enzo Biagi – Salaborsa” in Piazza del Nettuno
3, Bologna.
In the basement of Salaborsa is located the Auditorium.
How to get here:
by bus: lines and timetables on the
website www.tper.it
by car: located in restricted traffic zone
ZTL. Ring road exits n. 11/11bis-12
direction city center.
Entrance
Coffee Breaks and Lunch
Coffee breaks and lunch will be served in the Conference Venue.
Delegates must wear their badges in order to have access to the catering area.
Social Dinner
A social dinner has been organized on September 10,
2015 in Palazzo Gnudi.
This former palace dating from the first half of the XIV
Century is now a prestigious and perfectly equipped to
stage cultural events, lectures and conferences of various
kinds.
Located in Bologna, via Riva di Reno 75/77, it is a
historical building of the neoclassical style and it
belonged to the family Gnudi for centuries.
How to get here:
By bus: lines and timetables on the
website (www.tper.it)
By car: located in restricted traffic zone
ZTL. Ring road exit 5 direction city
center.
SCIENTIFIC PROGRAM ARRANGEMENTS
SESSION LIST
Session 1: Fundamentals - Nucleation and Growth Kinetics
Chair: Hans Erik Lundager Madsen
Session 2: Theory and Modeling
Chair: Liliana Braescu
Session 3: Product and Process Design of Pharmaceuticals and Fine Chemicals
Chair: Kevin Roberts
Session 4: Bulk Crystal Growth
Chairs: Janis Virbulis, Ewa Talik
Session 5: Advance in crystal growth technology
Chairs: Evgeny Zharikov, Christiane Frank-Rotsch
Session 6: Mesocrystals and Nonclassical Crystallisation / Growth of Biological Materials and
Biologically-Controlled Growth
Chairs: Damir Kralj, Jaime Gómez Morales
Session 7: In-situ Monitoring / Control of Crystal Growth Processes / Crystal morphology
Chairs: Alexander van Driessche, Carlos M. Pina
Session 8: Epitaxial Growth - Crystal growth interfaces
Chairs: Josef Novak, Luca Seravalli
Session 9: Fundamentals - Structural Defects and their characterization in Crystalline Materials
Chairs: Thierry Duffar, Bogdan Ranguelov
Session 10: Nanostructures & Nanoporous Crystals
Chair: Florinda Costa
Session 11: Novel materials and structures
Chairs: Peter Gille, Harri Lipsanen
POSTER SESSIONS
Poster Presentation Guideline:
1) The poster displaying space is 95 cm wide by 115 cm high.
2) Display your poster by yourself in the morning of your poster session in the designated panel; your
presentation number will be indicated on the panel. Please use pushpins prepared to put up your
presentation on the poster board.
3) Remove your poster at the evening of your poster session. Materials left on the poster boards after the
removal deadlines will be thrown away.
Poster session A:
Date: 9-11-2015, 13:45 – 15:45
Posters of the scientific sessions:
Session 1: Fundamentals - Nucleation and Growth Kinetics
Session 2: Theory and Modeling
Session 3: Product and Process Design of Pharmaceuticals and Fine Chemicals
Session 4: Bulk Crystal Growth
Session 5: Advance in crystal growth technology
Poster session B:
Date: 10-11-2015, 13:30 – 15:30
Posters of the scientific sessions:
Session 6: Mesocrystals and Nonclassical Crystallisation / Growth of Biological Materials and BiologicallyControlled Growth
Session 7: In-situ Monitoring / Control of Crystal Growth Processes / Crystal morphology
Session 8: Epitaxial Growth - Crystal growth interfaces
Session 9: Fundamentals - Structural Defects and their characterization in Crystalline Materials
Session 10: Nanostructures & Nanoporous Crystals
Session 11: Novel materials and structures
PRIZES
Several awards are reserved for student poster presentations:
The council of the German Association of Crystal Growth (DGKK) awards a prize for the
best poster of master and PhD students, who attend the school and present a poster at the
conference.
The prize will be 250,00 Euro
The council of the Italian Association oc Crystallography (AIC) awards a prize for the
best poster of master and PhD students.
The prize will be 250,00 Euro
Elsevier awards 3 poster prizes one for each section of the Handbook of Crystal
Growth(2nd edition): Fundamentals, Bulk Crystal Growth and Thin Film and Epitaxy.
The prizes are the corresponding volumes of the category.
Poster prizes will be announced during the social dinner.
PLENARY LECTURES
WEDNESDAY 9 September 2015
09:15-10:00
"The Joys and Challenges of Macromolecular Crystallization"
Professor NAOMI CHAYEN
Professor of Biomedical Sciences
Faculty of Medicine, Department of Surgery & Cancer, Imperial College, London
THURSDAY 10 September 2015
09:00-09:45
"Blue light emitting diodes: when growth and physics go together"
Professor NICOLAS GRANDJEAN
PhD - ICMP Director
Institute of Condensed Matter Physics (ICMP)
Ecole polytechnique fédérale de Lausanne (EPFL)
MEETING TIMETABLE
PROGRAM
TUESDAY 8 September 2015
Auditorium Enzo Biagi – Sala Borsa
17:00
Registration Open
18:30
Welcome Cocktail
WEDNESDAY 9 September 2015
09:00-09:15
Opening
Giuseppe Falini, Department of Chemistry «Giacomo Ciamician», University of Bologna
Andrea Zappettini, Institute of Materials for Electronics and Magnetism, CNR, Parma
09:15-10:00
Plenary lecture I
Chair: Simona Fermani
"The Joys and Challenges of Macromolecular Crystallization"
Naomi Chayen, Faculty of Medicine, Department of Surgery & Cancer, Imperial College, London
Room 215
10:00-11:05
SESSION 1a: Fundamentals of Nucleation and SESSION 9a: Fundamentals - Structural
Defects and their characterization in
Growth Kinetics
Crystalline Materials
Chairs: Thierry Duffar & Bogdan Ranguelov
10:00-10:20
“Numerical Modelling of Liquid Phase Diffusion "Cellular dislocation patterns in “Mono-like”
silicon grown by seeded directional solidification
growth of SiGe with uniform compositions”
of the melt "
Keynote: Dost Sadik, M. Sakhon, N. Armour
Keynote: Vanessa Amaral de Oliveira, Marina
Rocha, Thu-Nhi-Tran-Thi, Maria Tsoutsouva,
José Baruchel, Denis Camel
10:20-10:35
“Nonstoichiometry problems of AIIBVI vapor
“An in situ view of nucleation”
De Yoreo, James J., Ma, Xiang, Nielsen, Michael grown crystals"
Avetissov Igor, Andrew Khomyakov, Albert
H., Chen, Chun-Long
Davydov, Elena Mozhevitina, Vladimir
Chegnov, Nikolai Zhavoronkov
10:35-10:50
“Homogeneous nucleation in small droplets near "Influence of growth conditions on the optical,
mechanical and electrophysical properties the
critical supercooling”
lanthanum-gallium silicate group crystals"
Zdeněk Kožíšek, Pavel Demo
Buzanov Oleg, Kozlova Nina, Kozlova Anna,
Zabelina Evgeniya, Siminel Nikita, Spassky
Dmitriy
10:50-11:05
“Separation of nucleation and growth stages - a
way for studying crystal nucleation kinetics and to
rule a crystallization process designed to reduce
crystal polydispersity”
Nanev Christo Nanev, Tonchev Vesselin D.
11:05-11:25
"Micro-structural characterization of directionally
solidified eutectic oxides"
Cherif Maya, Gourav Sen, Vicky Vikram Das,
Laurent Carroz, Omar Benamara, Michel
Parlier, Thierry Duffar
Coffee break
Room 215
11:25-12:45
SESSION 1b: Fundamentals of Nucleation and SESSION 9b: Fundamentals - Structural
Growth Kinetics
Defects and their characterization in
Crystalline Materials
Chairs: Thierry Duffar & Bogdan Ranguelov
11:25-11:45
“Beams and Blocky Crystals: Another Challenge "Towards bulk cubic silicon carbide: Growth
mechanisms and related defects"
from the Naica Giant Crystals”
Keynote: Otálora Fermin, Joaquín Criado, Juan- Keynote: Yakimova Rositsa
Manuel Garcia-Ruiz
11:45-12:00
“Origin of energy efficiency of axial vibration "Second-phase
particle
migration
via
Temperature Gradient Zone Melting"
control technique in melt growth process”
Zharikov Evgeny, Andrey Sadovskiy, Ekaterina Kerry Wang, Andrew Yeckel, Jeffrey J. Derby
Sukhanova, Vladimir Kostikov, Igor Avetissov
12:00-12:15
“Growth of branched rutile-type TiO2 via self- "Effects of Annealing Treatments on
Microstructures of Aluminum Nitride Buffer
assembly and crystal twinning”
Layer Grown by MOVPE"
Jordan Vanja, Rečnik Aleksander
Kuwano Noriyuki, Kaur Jesbains, Fukuda
Junya, Soejima Yohei, Mitsuhara Masatoshi,
Suzuki Shuhei, Miyake Hideto, Hiramatsu
Kazumasa, Fukuyama Hiroyuki
12:15-12:30
“Selective crystallisation of the more stable ß "The role of screw dislocations in habit
polymorph of L-glutamic acid in an acoustic modification of KDP by impurity"
Lai Xiaojun, Kevin Roberts, Helmut Klapper
levitator”
Rusin Michal, Ristic Radoljub Ivan, Gnutzmann
Tanja, Emmerling Franziska
12:30-12:45
“Enhanced Crystallization Efficiency of an Active "The role of twin boundaries in growth of natural
Pharmaceutical Ingredient through the Formation and Fe-doped SnO2 crystals"
of Micron-Sized Crystals in the Undersaturated Tominc Sara, Nina Daneu, Aleksander Rečnik
State”
Rimez Bart, Edith Norrant, Benoît Haut, Benoit
Scheid
12:45-13:45
Lunch
13:45-15:45
Poster Session A: from Session 1 to Session 5
15:45-16:00
16:00-18:10
Coffee break
Room 215
SESSION 4a: Bulk Crystal Growth
Chairs: Janis Virbulis & Ewa Talik
SESSION 10: Nanostructures & Nanoporous
Crystals
Chair: Florinda Costa
16:00-16:20
“A new large-lattice-constant perovskite substrate
crystal”
Keynote: Uecker, Reinhard, Klimm, Detlef,
Bertram, Rainer, Guguschev, Christo, Brützam,
Mario, Kwasniewski, Albert, Klupsch, Michael,
Gesing, Th.M., Schlom, D.G.
"Nucleation approach to polytypism in III-V
nanowires"
Keynote: Jonas Johanson, Zeila Zanolli,
Kimberly A. Dick
16:20-16:40
“Floating-zone Growth of Large Single-Crystal of
Haldane Chain Compound SrNi2V2O8”
Keynote: A.T.M. Nazmul Islam, B. Lake, A.K.
Bera, B. Klemke, E. Faulhaber, J.M. Law, A.
Schneidewind, J.T. Park, E. Wheeler
"InAs/GaAs
sharply-defined
axial
heterostructures in self-assisted nanowires"
D. Scarpellini, C. Somaschini, A. Fedorov,
Sergio Bietti, C. Frigeri, V. Grillo, L. Esposito,
M. Salvalaglio, A. Marzegalli, F. Montalenti, E.
Bonera, P. G. Medaglia, S. Sanguinetti
16:40-16:55
“Europium and potassium co-doped strontium
metaborate single crystals grown by the
Czochralski method”
Głowacki Michal, Solarz Piotr, RybaRomanowski Witold, Martín Inocencio R.,
Diduszko Ryszard, Berkowski Marek
"Mass-transport driven growth dynamics of
AlGaAs shells deposited by metalorganic vapor
phase epitaxy around dense GaAs nanowire
ensembles"
Ilio Miccoli, Paola Prete, Nico Lovergine
16:55-17:10
“Flux growth and characterization of highly Yb3+substituted cubic RE2O3 (RE=Gd, Y, Lu) laser
crystals and of cubic Lu1.56Gd0.41Eu0.03O3 crystals”
Matias Velázquez, Philippe Veber, Gabriel Buşe,
Yannick Petit, Philippe Goldner, Olivier Plantevin,
Daniel Rytz, Emmanuel Véron, Rekia Belhoucif,
Véronique Jubera, Patrick Aschehough, Gérard
Aka
"Low Temperayure Growth of Porous ZnO
Films for Inorganic–Organic Hybrid Solar Cells"
Yoshino Kenji, Akiko Mochihara, Himeka
Tominaga, Youei yamaga, Takashi Minemoto,
Shigeru Ikeda
17:10-17:25
“On the crystal growth of incongruent borate type
crystal LaxGdyScz(BO3)4 (x + y + z = 4) by the
Czochralski method”
Lucian Gheorghe, Flavius Voicu, Gabriela
Salamu, Federico Khaled, Alexandru Achim,
Cristina Gheorghe, Pascal Loiseau, Nicolaie
Pavel, Gérard Aka
"Growth of ZnO nanostructures through rapid
crystallization"
Fioravanti Ambra, Bonanno Antonino, Carotta
Maria Cristina, Sacerdoti Michele
17:25-17:40
“Improvement of crystal growth of Li4SiO4 single "Heat of Fusion of Nano Crystals"
crystals for neutron detection and their scintillation Clain Alexander E., Novins Caleb A., Amanuel
Samuel
and luminescence properties”
Jan Pejchal, Vladimir Babin, Alena Beitlerova,
Shunsuke
Kurosawa,
Yuui
Yokota,
Akira Yoshikawa, Martin Nikl
17:40-17:55
“Synthesis and characterization of Ba2Cu1- "Filamentary growth of metals"
xNixGe2O7, x =0, 0.1 single crystals grown by Richter Gunther
floating zone technique”
Fittipaldi Rosalba, Rocco Luisa, Ciomaga
Hatnean Monica, Granata Veronica, Lees Martin,
Balakrishnan Geetha, Vecchione Antonio
17:55-18:10
“Crystallization of Al2O3-YAG-ZrO2 eutectic “A comparative numerical analysis of circular
and rectangular well nanopatterning on c-plane
ceramic plates by the EFG technique”
Laurent Carroz, Maya Cherif, Nicolas Barthaley, sapphire substrates for selective area growth of
José Peirrera, Thierry Duffar
AlN islands”
M. Chitra, I. Davis Jacob
Room 215
18:10-19:10
Meeting Delegates ENCG
THURSDAY 10 September 2015
09:00-09:45
Plenary lecture II
Chair: Roberto Fornari
"Blue light emitting diodes: when growth and physics go together"
Nicolas Grandjean, ICMP, Ecole polytechnique fédérale de Lausanne
Room215
09:45-10:50
SESSION 4b: Bulk Crystal Growth
SESSION 5a: Advance in Crystal Growth
Technology
Chairs: Evgeny Zharikov & Christiane FrankRotsch
09:45-10:05
“New results in adsorption at semiconductor
surfaces - consequences to growth and doping of
semiconductor from the vapor”
Keynote: Krukowski Stanisław, Pawel Kempisty,
Pawel Strąk, Maria Ptasinska, Jacek Piechota
“Numerical modeling and experimental
validation of electromagnetical stirring in
unidirectional solidification of multicrystalline
silicon”
Keynote: Negrila Radu Andrei, Popescu
Alexandra, Vizman Daniel
ù10:05-10:20
“Range of the temperature gradients and the
growth rate values in the growth of CZT crystals
from the melt”
Repiso Eva, Corrochano Álvaro, Rubio Sandra,
Plaza Jose Luis, Tsybrii Zinoviia, Vuichyk Mykola,
Dieguez Ernesto
“Crystal Growth of Cd1-xZnxTe by the Traveling
Heater Method in Microgravity on Board of
Foton-M4 Spacecraft”
Borisenko Elena B., N. N. Kolesnikov, A. S.
Senchenkov, M. Fiederle
10:20-10:35
“Growth and Performance of Large ZnGeP2
Single Crystals”
Chunhui Yang, Zuotao Lei, Chongqiang Zhu,
Liangcheng Song
“Modified Bridgman technique for growing Sbbased binary compounds”
Pillaca Quispe Mirtha, Miller Wolfram,
Cocivera Viviane, Maletin Tamara, Gille Peter
10:35:10:50
“Crystal growth, physical properties and
applications of mixed and complex halides”
Edith Bourret, Zewu Yan, Eric Samulon, Tetiana
Shalapska and Didier Perrodin
Appendix to SESSION 10:
"Dual-Type
Compound
Semiconductor
Nanowire Arrays"
Joona-Pekko Kakko, Farid Bayramov, Bakhysh
Bairamov, Tuomas Haggrén, Veer Dhaka,
Teppo Huhtio, Antti Peltonen, Hua Jiang, Esko
Kauppinen, Harri Lipsanen
10:50-11:10
11:10-12:30
Coffee break
Room 215
SESSION 4c: Bulk Crystal Growth
SESSION 5b: Advance in Crystal Growth
Technology
Chairs: Evgeny Zharikov & Christiane FrankRotsch
11:10-11:30
“Modeling of dopant transport in gas and melt
during silicon FZ crystal growth”
Keynote: Sabanskis Andrejs, Surovovs Kirils,
Virbulis Jānis
“Experimental evidence that a high electric field
acts as an efficient external parameter during
crystalline growth of bulk oxide”
Keynote: Haumont Raphaël, P. Hicher, R.
Saint-Martin, X. Mininger, P. Berthet
11:30-11:45
“Impact of growth rate fluctuations on the bulk
quality of Czochralski silicon crystals”
Gaspar Guilherme, Lanterne Adeline, Jensen
Øyvind, Lehmann Toni, Hagen Vegard, Kildemo
Morten, Di Sabatino Marisa, Arnberg Lars, Øvrelid
Eivind
“High-pressure and ambient gas effect on the
optical floating zone crystal growth of novel
oxide and intermetallic compounds”
Sass Paul, Robert Schöndube
11:45-12:00
“Reduction of carbon contamination during the
melting process of Czochralski silicon crystal
growth”
Xin Liu, Bing Gao, Satoshi Nakano and Koichi
Kakimoto
“Growth of Shaped Oxide Eutectics by the EFG
Technique”
Stryukov Dmitry, Shikunova Irina, Kurlov
Vladimir
12:00-12:15
“N-type doping of bulk gallium nitride grown by “High-pressure crystallization of organic
hydride vapour phase epitaxy”
compounds in a diamond-anvil cell”
Patrick Hofmann, Frank Habel, Martin Krupinski, Andrzejewski Michal, Andrzej Katrusiak
Gunnar Leibiger, Franziska Christine Beyer,
Stefan Eichler, Thomas Mikolajick
12:15-12:30
“Growth of 5 kg-level LBO for ultrashort and “Direct measurement of the crystallization
ultrahigh power laser”
pressure at the pore scale”
Zhanggui Hu, Yinchao Yue, Ying Zhao, Heng Tu Desarnaud Julie, Daniel Bonn, Noushine
Shahidzadeh
12:30-13:30
Lunch
13:30-15:30
Poster Session B: from Session 6 to Session 11
15:30-15:50
Coffee break
Room 215
15:50-18:00
SESSION 2a: Theory and Modeling
SESSION 8a: Epitaxial Growth - Crystal Growth
Interfaces
Chairs: Josef Novak & Luca Seravalli
15:50-16:10
“Collaboration of atomic and macro scale
calculations: polytype and defect control of wide
bandgap material”
Keynote: Koichi Kakimoto, Bing Gao, Shin-ichi
Nishizawa, Satoshi Nakano, Yoshihiro Kangawa
"Analysis of critical thickness for generated
misfit dislocation in GaInN/GaN superlattice on
GaN by in situ X-ray diffraction"
Keynote: Ohsumi Junya, Koji Ishihara, Taiji
Yamamoto, Motoaki Iwaya, Tetsuya Takeuchi,
Satoshi Kamiyama, Isamu Akasaki
16:10-16:30
“Gaining understanding of crystal growth
processes via modeling: Pushing the continuum
from the top down”
Keynote: Yutao Tao, Andrew Yeckel, Jeffrey J.
Derby
“In situ observation of low temperature growth
of Ge on Si(111) via RHEED”
Keynote: Grimm Andreas, Andreas Fissel,
Eberhard Bugiel, H. Jörg Osten, Tobias F.
Wietler
16:30-16:45
“Study on the usage of a commercial software
(Comsol
multiphysics®)
for
dislocation
multiplication model”
B. Gallien, M. Albaric, J.P. Garandet, Thierry
Duffar, K. Kakimoto, M. M’Hamdi
16:45-17:00
“Atomic scale design of epitaxial interfaces: "Two-dimensional Si/Si(111)-(7×7) nucleation
affected by step permeability and sink to atomic
clusters, stripes and nanowires”
steps"
Michail Michailov, Bogdan Ranguelov
Rogilo Dmitry, Fedina Liudmila, Kosolobov
Sergey, Ranguelov Bogdan, Latyshev
Alexander
17:00-17:15
“Numerical analysis of dislocation density in
multicrystalline silicon for solar cells using
experimental verification”
Satoshi Nakano, Bing Gao, Karolin Jiptner,
Hirofumi Harada, Yoshiji Miyamura, Takashi
Sekiguchi, Masayuki Fukuzawa, Koichi Kakimoto
"Epitaxial growth of Ge/Si nanostructures on Si
surface patterned by ion irradiation"
Smagina Zhanna Victorovna, A.V. Zinovyev,
N.P. Stepina, A.F. Zinovieva, S.A. Rudin, P.L.
Novikov, V.A. Seleznev, A.V. Dvurechenskii
17:15-17:30
“Numerical Modeling of Titanium Distribution in
Sapphire Crystals Grown by the Kyropoulos
Method”
Carmen Stelian, Gourav Sen, Nicolas Barthalay,
Thierry Duffar
"Self-assembled strained GeSi nanoscale
structures grown by MBE on Si(100)"
Nikiforov Alexandr, Vyacheslav Timofeev,
Artur Tuktamyshev, Michail Esin, Serge Teys,
Oleg Pchelyakov
17:30-18:45
“Evolution of grains during solidification of silicon
– attempts of numerical simulations for an
understanding”
Miller Wolfram, Popescu Alexandra
"Quantum dot chains in InAs/GaAs multistacked
structures grown by MBE: a strain analysis by
FEM"
Latini Valerio, Placidi Ernesto, Arciprete
Fabrizio, Magri Rita, Patella Fulvia
17:45-18:00
“Analytic scaling function for size distributions of
2D surface islands”
Vladimir G. Dubrovskii, N. V. Sibirev, Yu. S.
Berdnikov
“A study of β-Ga2O3 hetero-epitaxial layers
grown by MOCVD and ALD”"
F. Boschi, M. Bosi, E. Buffagni, T. Berzina, C.
Ferrari, Fornari Roberto
20:00
“Structural and electrical characteristics of
AlGaN/GaN heterostuctures with thin AlN
interlayer on sapphire substrate grown by
MOCVD"
Raju Ramesh, Kandasamy Prabakaran, Ravi
Loganathan, Manavaimaran Balaji, Eric
Faulques, Alexandre Crisci, Krishnan Baskar
Social Dinner
FRIDAY 11 September 2015
Room 215
09:00-11:10
SESSION 11: Novel Materials and Structures
Chairs: Peter Gille & Harri Lipsanen
SESSION 3: Product and Process Design of
Pharmaceuticals and Fine Chemicals
Chair: Kevin Roberts
09:00-09:20
“In-situ observations of the catalytic growth of “Using crystal growth to generate single
chirality from an achiral start”
nanomaterials”
Keynote: Rene Steendam, Jorge Verkade, Tim
Keynote: Hofmann Stephan
van Benthem, Hugo Meekes, Willem van
Enckevort, Jan Raap, Floris Rutjes, Elias Vlieg
09:20-09:35
“Crystal engineering of molecular solids: “light“ “Crystallisation Characteristics of an Organic
interactions for interactions with light”
Material in Industrial Mother Liquor with
Grepioni Fabrizia, Simone d'Agostino, Dario Impurities”
Braga, Barbara Ventura, Mirko Seri
Keynote: Khan Shahid, Mahmud Tariq,
Roberts Kevin, Zhu Xiaofeng, George Neil,
Sillers Pauline
09:35-09:50
“Chemical Vapor Transport towards new geoinspired selenite-based materials”
Colmont Marie, Minfeng Lü, Almaz Aliev, Jacob
Olchowka, Marielle Huvé, Olivier Mentré
“Preferential
Orientation
of
β-phase
Triacylglycerol on Graphite Surface”
Fumitoshi Kaneko, Shinichi Yoshikawa,
Haruyasu Kida, Kiyotaka Sato
09:50-10:05
“Spectroscopic examinations of Lu3Al5O12:Pr
single crystals”
Guzik Adam, Talik Ewa, Pajączkowska Anna,
Szubka Magdalena, Kusz Joachim, Balin
Katarzyna, Urbanowicz Piotr
“Crystallization of L-Glutamic acid polymorphs
in stirred and stagnant conditions”
Tahri Yousra, Gagnière Emilie, Chabanon
Elodie, Bounahmidi Tijani, Mangin Denis
10:05-10:25
“Crystal growth from high-pressure melt and
Chemical
Vapor
Transport
of
(Si,Ge)
monopnictides, a new family of 2Dsemiconductors”
Keynote: Barreteau Céline, Baptiste Michon,
Enrico Giannini
“Design of Optimal Start-up Procedures for
MSMPR Crystallizers”
Kamaraju Vamsi Krishna, Power Graha, Hou
Guangyang, Zhao Yan, Glennon Brian
10:25-10:40
“Superconductivity in single crystals of alkali metal
intercalated iron chalcogenides”
A. Krzton-Maziopa, E. Pomjakushina, Conder
Kazimierz
“A phenytoin polymorph accessible via surface
mediation”
Daniela Reischl, Christian Röthel, Eva Roblegg,
Heike M.A. Ehmann, Oliver Werzer
10:40-10:55
“Crystal growth of rare earth containing clathrates
and mechanism of rare earth incorporation into the
clathrate cages”
Prokofiev Andrey, Robert Svagera, Monika
Waas, Johannes Bernardi, Silke Paschen
“Nucleation Kinects of Co-crystal by
Simultaneous Monitoring of Dissolution and
Crystallisation
using
Process
Raman
Technique: Precipitation of Burkeite”
Boyang Zou, Xiaojun Lai, Dan Xu, Luis Martin
de Juan
10:55-11:10
“Flux growth at 1230°C of cubic Tb2O3 single "Continuous production of lactose monohydrate
crystals and characterization of their optical and crystal seed suspensions by rapid antisolvent
crystallization using a continuous nucleation
magnetic properties”
Velázquez Matias, Philippe Veber, Grégory unit”
Gadret, Olivier Plantevin, Daniel Rytz, Mark Peltz, Pól MacFhionnghaile, John McGinty, Jan
Sefcik
Rodolphe Decourt
11:10-11:30
Coffee break
11:30-13:40
Room 215
SESSION 7: In-situ Monitoring ⁄ Control of Crystal SESSION 6: Mesocrystals and Nonclassical
Crystallisation ⁄ Growth of Biological
Growth Processes ⁄ Crystal morphology
Materials and Biologically-Controlled Growth
Chairs: Alexander van Driessche & Carlos M. Pina Chairs: Damir Kralj & Jaime Gómez Morales
11:30-11:50
“Mechanistic insights into the early stages of "Multiscale Approach of the Bio Crystal Status
crystallization of rare-earth carbonates"
and Growth in Mollusc Shells"
Keynote: Rodriguez-Blanco Juan Diego, Keynote: Baronnet Alain
Dideriksen, Knud, Tobler, Dominique J., Sand,
Karina K., Vallina, Beatriz, Benning, Liane G.,
Stipp, Susan
11:50-12:10
"From Amino Acids to Cements: Crystallization
Studied by CLASSIC NMR"
Keynote: Hughes Colan, Williams, P. Andrew;
Keast, Victoria L.; Edwards-Gau, Gregory R.;
Charalampopoulos, Vasileios G.; Harris, Kenneth
D. M.; Gardner, Laura J.; Walling, Sam A.; Bernal,
Susan A.; Provis, John L.
"Bio-inspired Composite Crystals. Incorporation
of nanoparticles in calcite and zinc oxide single
crystal"
Keynote: Kulak Alexander, Pengcheng Yang,
Mona Semsarilar, Oscar Cespedes, Yi-Yeoun
Kim, Steven P. Armes, Fiona C. Meldrum
12:10-12:25
"An Investigation into the Particle Growth Pathway
of Precipitated Fenofibrate"
Tierney Teresa, Rasmuson, Åke C., Hudson,
Sarah P.
"Optimization of Crystallization using Dialysis
Combined with Temperature Control"
Niels Junius, Esko Oksanen, Maxime Terrien,
Christophe Berzin, Jean-Luc Ferrer, Budayova
- Spano Monika
12:25-12:40
"Growth of nanostructured carbon materials by
Supersonic Molecular Beams of C60 on Cu
studied by Surface Electron Spectroscopies"
Aversa Lucrezia, Tatti Roberta, Taioli Simone,
Garberoglio Giovanni, Speranza Giorgio,
Cavaliere Emanuele, Gavioli Luca, Iannotta
Salvatore, Verucchi Roberto
"Influence of shear rate and surface area on
nucleation kinetics in aqueous solutions of
glycine and urea reveals nonclassical
nucleation mechanisms"
Carol Forsyth, Danielle Trap, Sefcik Jan
12:40-12:55
"Grain growth competition in directionally solidified
multi-crystalline silicon studied with in situ X-ray
imaging techniques"
Thècle Riberi-Béridot, Nathalie Mangelinck-Noël,
Amina Tandjaoui, Guillaume Reinhart, Maria
Tsoutsouva, Gabrielle Regula, José Baruchel
"Infrared light-induced protein crystallization"
Kowacz Magdalena, Marchel Mateusz,
Juknaitė Lina, Esperança José M. S. S., Romão
Maria João., Carvalho Ana Luísa., Rebelo Luís
Paulo N.*
12:55-13:10
"Evaporation Crystallization of Glycine"
Puranen Johanna, M. Louhi-Kultanen
"Precursor-based bioinspired synthesis of
magnetite nanocrystals"
Mirabello Giulia, Söğütoğlu Leyla-Can,
Lendesr Jos J.M., Sommerdijk Nico A.J.M
13:10-13:25
"Polymer versus monomer action on the growth
and habit modification of sodium chloride crystals"
Townsend Ellie, W.J.P. van Enckevort, J.A.M.
Meije, E. Vlieg
"Co-processing of Metformin Hydrochloride with
Hydroxypropyl Methylcellulose and Sodium
Carboxymethlycellulose during Crystallization to
Manufacture Extended Release Tablets"
Erdemir Lee Deniz, Chang Shih-Ying, Wong
Benjamin, Rosenbaum Tamar, Kientzler
Donald, Wang Steve, Desai Divyakant, Kiang
San
13:25-13:40
"Application of LPE method for producing of highperformance scintillating screens based on the
single crystalline films of multicomponent garnets"
Yu. Zorenko, T. Zorenko, V. Gorbenko, T.
Voznyak, O. Sidletskiy, Ya. Gerasymov, A.
Fedorov
"Heterogeneous nucleation and growth of
calcium phosphate films on mica sheets by
vapour diffusion"
Gómez Morales Jaime
13:40-14:30
14:30-16:25
Lunch
Room 215
SESSION 2b: Theory and Modeling
SESSION 8b: : Epitaxial Growth - Crystal
Growth Interfaces
Chairs: Josef Novak & Luca Seravalli
14:30-14:50
“On Modeling Interface Attachment Kinetics in “Step density waves on vicinal crystal surfaces"
Melt and Solution Growth Systems”
Keynote:
Keynote: Oleg Weinstein, Oren Bass, Alexander Ranguelov Bogdan Stavrev, Stoyan Stoyanov
Virozub, Andrew Yeckel, Wolfram Miller, Jeffrey J.
Derby, Simon Brandon
14:50-15:10
“Tailoring crystal growth more and more “Structural study of the innovative 3C-SiC/Si/3C
quantitatively via multiscale simulations”
SiC/Si heterostructure for electro-mechanical
Keynote: Heike Emmerich
applications"
Keynote: Khazaka Rami, J.F. Michaud, P.
Vennéguès, D. Alquier, M. Portail
15:10-15:25
“Phase field simulations of particle capture during
directional solidification of silicon for solar cells”
Heike Emmerich, Hörstermann Henning, Kundin
Julia, Friedrich Jochen, Azizi Maral, Reimann
Christian, Cröll Arne, Jauß Thomas, Sorgenfrei
Tina
"Functionalization of SiC Nanowires by
Supersonic Molecular Beams for Photodynamic
Therapy"
Tatti Roberta, Aversa Lucrezia, Verucchi
Roberto, Fabbri Filippo, Rossi Francesca,
Attolini Giovanni, Bosi Matteo, Salviati
Giancarlo, Iannotta Salvatore
15:25-15:40
“Phase-field study of morphological evolution
during directional solidification: influence of
temperature gradient and convection”
Ankit Kumar, Selzer, Michael, Bhattacharya,
Avisor, Nestler, Britta
"Characterisation of sub-micrometer yttrium iron
garnet LPE films with low ferromagnetic
resonance losses"
Dubs Carsten, Surzhenko Oleksii, Linke Ralf,
Jauß Thomas, Danilewsky Andreas
15:40-15:55
“Phase Field Crystal Modeling of Heterogeneous
Nucleation and Heteroepitaxy”
László Gránásy, Frigyes Podmaniczky, Gyula I.
Tóth, György Tegze, Tamás Pusztai
"Liquid phase epitaxial growth of GdAP and
GdLuAP scintillating films for synchrotron
imaging"
Riva Federica, Douissard Paul-Antoine, Martin
Thierry, Zorenko Yuriy, Petrosyan Ashot,
Dujardin Christophe
15:55-16:10
“Phase-field Modelling of Spiraling Ternary
Eutectic Dendrites”
László Rátkai, Tamás Pusztai, Attila Szállás,
László Gránásy
"Controlling Polymorphism in Organic Thin
Films by Light"
Pithan Linus, Caterina Cocchi, Christopher
Weber, Anton Zykov, Sebastian Bommel,
Steven J. Leake, Peter Schäfer, Claudia Draxl,
Stefan Kowarik
16:10-16:25
“Time Evolution of 2D Cellular Automata with
“Crystal Growth” Rules”
Alexander Kolevski, Hristina Popova, Georgi As.
Georgiev, Vesselin Tonchev
"PDIF-CN2 organic thin-film deposited at room
temperature by supersonic molecular beam
deposition for n-type OTFT"
Chiarella Fabio, Barra Mario, Chianese
Federico, Toccoli Tullio, Cassinese Antonio
16:25
Final greetings
POSTER PRESENTATIONS
1 - Fundamentals of Nucleation and Growth Kinetics
S01-P02 - Experimental research of phase transitions in a liquid melt of high-purity aluminum
Borisovith, Vorontsov Vadim
S01-P03 - On the Theory of Ostwald Ripening: Formation of the Universal Distribution Function in the Presence of Different Mass
Transfer Mechanisms
Alexandrov, Dmitri V
S01-P04 - Influence of shear rate on nucleation in oscillation baffled crystallizer.
Yang, Huaiyu
S01-P05 - Interferometric Observation of Concentration Field during the Growth of Tetrahydrofuran Clathrate Hydrate in the
Guest/Host Boundary Layer.
Nagashima, Kazushige
S01-P06 - Study of crystallization processes in Bi-doped As2S3 chalcogenide glasses using linear isoconversion methods.
Lukic-Petrovic, Svetlana
S01-P08 - Influence of ionic surfactants on sodium chloride crystallization during evaporation.
Qazi, Mohsin Jahan
S01-P09 - A Study of Crystal Growth of Salicylic Acid in Organic Solvents.
Jia, Lijun
S01-P10 - "Influence of sintering aid (SiO2) on optical properties of ceramic YAG:Cr,C".
Chaika Mihail
S01-P11 - Laser-Induced Nucleation in Continuous Flow.
Mackenzie, Alasdair Morgan
S01-P13 - Understanding of Crystallization and Growth of LiB3O5 crystal in the MoO3-based high-temperature solution at the
Molecular Level.
Wang, Di
S01-P14 - Growth of doped KDP single crystals from solutions with KMnO4 additives.
Egorova, Anna
S01-P15 - Study on Growth Kinetics of Partially Deuterated Potassium Dihygrogen Phosphate (p-DKDP) Crystals for High Power
OPCPA.
Guzman, Luis A.
S01-P16 - Thinning and thickening of free-standing smectic films.
Pikina, Elena
S01-P17 - In-situ SAXS studies of crystal structures of C16/C18 binary system during crystallisation and phase transformations in
melts.
Tang, Xue
S01-P18 - Solution state studies of C16H24/C18H38 binary system in dodecane from poly-thermal crystallisation process.
Tang, Xue
S01-P19 - Nucleation of Amine Soaps.
Booth, David
S01-P20 - Nucleation, crystal growth kinetics and morphology of methyl stearate as a function of solution environment.
Camacho Corzo, Diana Milena
S01-P21 - Metastability limit for the nucleation of NaCl crystals in confinement.
Shahidzadeh, Noushine
S01-P22 - The role of alanine, aspartic acid and lysine as simple models of organic matrix molecules participating in calcium
carbonate biomineralization.
Stajner, Lara
S01-P23 - Crystallization kinetics of iron inclusion in magnesium aluminosilicate glass processed by laser floating zone technique.
Ferreira, Nuno M.
S01-P24 - The NMR study of 3He enclosed in nanotubes MCM-41.
Fysun, Yana
S01-P25 - Block copolymer aggregates on planar substrates: Impact of preparation conditions and surface wettability.
Danglad Flores, José Angel
S01-P26 - Switching off Non photochemical laser induced nucleation by use of nanofiltration.
Kendall, Thomas Gilbert
2 - Theory and Modeling
S02-P01 - Atomic scale design of epitaxial interfaces: clusters, stripes and nanowires.
Michailov, Michail
S02-P02 - A single-domain approach to simulate the effect of convective flow on the mushy zone structure in Czochralski growth of
semitransparent oxide crystal.
Faiez, Reza
S02-P03 - Modeling of patterns by the phase field crystal method in three dimensions.
Starodumov, Ilya
S02-P04 - Kinetic Monte Carlo simulations of vicinal GaN(000-1) surface evolution during N-rich growth.
Krzyzewski, Filip
S02-P05 - Modeling of dendritic growth under earthly and reduced gravity conditions.
Galenko, Peter
S02-P06 - Relationship between stability of facet surfaces and incorporation of zinc-blende phase in InN during pressurized reactor
MOVPE: A theoretical approach.
Kusaba, Akira
S02-P07 - Study of the early stages of Calcium Phosphate nucleation in water by means of ab Initio Molecular Dynamics.
Mancardi, Giulia
S02-P08 - On obtaining equilibrium crystal shape under non stationary conditions.
Skorynina, Alina A.
S02-P09 - Working point of the EFG process.
Carroz, Laurent
S02-P11 - Kinetic model of cement hydration with time-dependent rates.
Valentini, Luca
S02-P12 - Crystal surface morphology as a consequence surface diffusion anisotropy.
Zaluska-Kotur, Magdalena Anna
S02-P13 - Monte Carlo simulation of island formation during GaAs(001) homoepitaxial growth.
Balakirev, Sergey Vyacheslavovich
S02-P14 - Mathematical modeling of the process of growing a single crystal CdTe 100 mm by the Obreimov-Shubnikov method.
Pavlyuk, Marina
S02-P16 - Experimentally Verified Numerical Simulation of Germanium Single Crystals Grown by the AVC-AHP Technique.
Yousefi, Pouya
S02-P17 - Microscopic modelling of confined crystal growth and dissolution.
Høgberget, Jørgen
S02-P18 - Dendritic Growth Kinetics in Undercooled Melts under Static Magnetic Fields.
Gao, Jianrong
S02-P19 - Multiphase-field theories of crystallization: A comparative study.
Toth, Gyula
S02-P21 - Thermoelectric Control of Crystal Growth.
Pericleous, Koulis
S02-P22 - Orientation-field model for polycrystalline solidification in binary alloys with a singular coupling between order and
orientation.
Korbuly, BÃ¡lint
S02-P23 - Rotationally-driven, axisymmetric oscillatory convection in a semitransparent Czochralski melt model.
Faiez, Reza
S02-P24 - Thermal stability and spontaneous breakdown of free-standing metal nanowires.
Giazitzidis, Paraskevas
S02-P25 - Towards the understanding of hydrozincite precipitation; Population balances on sparingly soluble compounds.
Martín-Soladana, Pablo Miguel
S02-P26 - Effects of boundary conditions and geometry on structural and thermodynamic properties of modeled semiconductors.
Podolska, Natalia
S02-P27 - The Conductivity Of Two-Dimensional Electron Crystal On The Surface of liquid 4He. Modeling.
Sharapova, Iryna
S02-P28 - Transitions between regimes of crystal growth kinetics under decaying supersaturation.
Tonchev, Vesselin Dimitrov
S02-P29 - Effect of surface reconstruction on Ge-Si(001) heteroepitaxy.
Ghosh, Paramita
S02-P30 - Interatomic distances and thermodynamic properties of wurtzite and zinc blende AlInGaN.
Podolska, Natalia
S02-P31 - A numerical model on nano-line patterning of c-plane sapphire substrates for selective area growth of AlN islands.
Jacob, Davis
S02-P32 - Modeling of axial heterostructure formation in multicomponent III-V nanowires.
Koriakin, Aleksandr
3 - Product and Process Design of Pharmaceuticals and Fine Chemicals
S03-P03 - Achiral molecules in engineering of non-centrosymmetric crystal structures: polymorphs and co-crystals of 1H-3,5dinitropyridine-2-one.
Fedyanin, Ivan
S03-P05 - Non-Photochemical LASER-Induced Nucleation in Water/Ethanol of sulfathiazole.
Li, Wenjing
S03-P06 - Purification of fermentatively produced specialty carbohydrates.
Bekers, Katelijne
S03-P12 - Crystallisation Characteristics of an Organic Material in Industrial Mother Liquor with Impurities.
Mahmud, Tariq
4 - Bulk Crystal Growth
S04-P01 - Bulk growth of optical quality inverted Solubility Li2SO4.H2O single crystals by the improved Sankaranarayanan Ramasamy method.
Silambarasan, A
S04-P04 - TSFZ-growth, magnetism and ac conductivity of LiMn(1-x)Fe(x)PO4 single crystals.
Neef, Christoph
S04-P06 - Czochralski growth of bulk Li2MoO4 crystals for the scintillating bolometers used in the rare events searches.
Velazquez, Matias
S04-P07 - Czochralski growth and physical properties characterizations of 6Li- and
cryogenic bolometers used in the rare events searches.
Velazquez, Matias
10B-enriched
crystals for heat-scintillation
S04-P09 - Influence of melt convection on the aggregation of inclusion in massive sapphire and garnet crystals for growing by HDC
method.
Tanko, Alina
S04-P10 - New insights on growth rate limitations of the Traveling Heater Method.
Derby, Jeffrey J.
S04-P11 - Growth and Laser performance of a new IR NLO crystal BaGa4Se7.
Yao, Jiyong
S04-P12 - Growth from the melt, structure and properties of the crystals of (ZrO2)1-x(Sc2O3)x solid solutions.
Kulebyakin, Alexey
S04-P13 - Bulk crystals of L-Histidinium dihydrogen phosphate orthophosphoric acid grown by Sankaranarayanan - Ramasamy
method.
Ittyachan, Reena
S04-P15 - Control of sapphire crystal morphology grown in a Kyropoulos furnace.
Sen, Gourav
S04-P16 - Influence of Growth Conditions in Interface shape and Stability in Antimony doped Germanium Single Crystals using VB,
AHP, and AVC Techniques.
Sheikhi, Aidin
S04-P19 - VGF growth of GaAs doped with 12C, 16O and 18O for the study of mid-infrared vibrational modes.
Frank-Rotsch, Christiane
S04-P20 - The search for novel solvents for the single crystal growth of germanate phases by the flux method.
Ivanov, Vladimir A.
S04-P21 - The reduction of basal plane dislocations by modifying thermal conductivity of the crucible during PVT growth of 4H-SiC
single crystals.
Miyazaki, Kazuma
S04-P22 - Dosimetric properties of luminescence crystals grown by Micro-Pulling Down Method.
Marczewska, Barbara
S04-P23 - Optical, Structural and Microhardness Properties of KDP Crystals Grown from L-arginine Doped Solutions.
Prytula, Igor M.
S04-P24 - Growth and point defect characterization of bulk AlN crystals.
Dittmar, Andrea
S04-P26 - Crystal growth of hexaferrits Z structure Ba(Sr)3 Co2 Fe24 O41 by floating zone melting.
Balbashov, Anatoly
S04-P27 - Mathematical modeling of the process of growing a single crystal CdTe 100 mm by the Obreimov-Shubnikov method.
Zykova, Marina
S04-P28- Features compensate defects in CdTe using a stepwise cooling of the crystal.
Pavlyuk, Marina
S04-P30 - Investigations on synthesis, growth and physical properties of AgGaInS2 single crystals for Mid-IR application.
N. Karunagaran
S04-P31 - Crystal Growth and Thermoelectric Properties of Sr2Fe2O5 Single Crystals.
Hossain, Md Anwar
S04-P33 - Magnetocaloric and Hopkinson effects in slowly and rapidly cooled Gd7Pd3.
Oboz, Monika
S04-P35 - Influence of growth parameters on electrical proprieties of highly polluted mc-Si grown by the Bridgman technique with
various crucible-coating combinations.
Negrila, Radu Andrei
S04-P40 - Optical properties of Cd1-xMnxTe:Fe2+ crystals.
Kapustnyk, Oleksii
S04-P41 - Growth of Bi2Te3, Cr2Ge2Te6 and CrSi2Te6 crystals for Topological Interests.
Chandran, Bagavath
S04-P42 - Characterization of G2-sized quasi-mono Si directionally solidified in TMF.
Kiessling, Frank M.
S04-P43 - β-Ga2O3 Crystals Grown from Al2O3-Ga2O3 Melt.
Nikolaev, Vladimir
S04-P44 - Growth, structural and magnetic characterization of highly ordered Co2FeSi single crystals.
Ramasamy, Mohankumar
S04-P45 - Effect of crucible geometry and fixed heat exchangers in the solid-liquid interface for growing CdZnTe bulk crystals using
a Vertical Gradient Freeze technique.
Dieguez, Ernesto
S04-P47 - High purity Germanium Crystal Growth.
Aravazhi, Shanmugam
S04-P48 - The influence of finite silicon electrical conductivity on melt flow and dopant transport in floating zone crystal growth
process.
Surovovs, Kirils
S04-P49 - 3D simulation of feed rod melting in floating zone silicon single crystal growth.
Plate, Matiss
S04-P50 - Crystal growth and characterization of an oxy-fluoride crystal (BaCaBO3 F) doped with Yb3+ ions for self-frequency
doubling: a thrilling challenge.
Khaled, Federico Nabil
S04-P51 - Ge-containing Quartz Single Crystals - New Advanced Piezoelectric Material.
Setkova, Tatiana
S04-P52 - Dislocation multiplication during Czochralski growth of germanium: Numerical studies and experimental results.
Miller, Wolfram
S04-P54 - New technological approaches for electroless deposition of metal contacts on CdZnTe single crystals.
Bettelli, Manuele
S04-P55 - Impurity distribution in characteristic of multicrystalline silicon growth mode.
Nepomnyashchikh, Aleksandr Iosifovich
S04-P56 - Growth of TbFe0.5Mn0.5O3 and Tb0.5Sr0.5MnO3 Single Crystals Using Optical Float-Zone Technique.
Hariharan, Nhalil
S04-P57 - SrMoO4:Ho3+:Tm3+ crystal as new active material for mid - IR laser.
Dunaeva, Elizaveta
S04-P59 - Structural properties and spinodal decomposition of bulk ternary semiconductor compounds with oxygen in the anion
sublattice.
Podolska, Natalia
S04-P60 - Li2MoO4 crystal growth from solution activated by low-frequency vibrations.
Sadovskiy, Andrey P
S04-P63 - Numerical modeling of a kyropoulos process to grow square silicon ingots for photovoltaic applications using different
configurations and different working parameters.
Nouri, Ahmed
S04-P64 - Effectivity of chemical vapor transport for ZnO single crystal growth based on HCl vapors.
Colibaba, Gleb V
S04-P66- Temperature dependent optical absorption of strontium titanate.
Kok, Dirk Johannes
5 - Advance in Crystal Growth Technology
S05-P01 - Isostructural phase transition of 2,4,5-triiodoimidazole at high pressure.
Rajewski Kacper Wojciech
S05-P02 - pH specific single crystal growth of N-Hδ+ Clδ- influenced [ZnCl4]- [R]+ hybrid materials of 3D to 2D lattice dimensionality by
organic variant: Microscopy, optical Eg and PL properties.
Jasrotia, Dinesh
S05-P04 - Heptadecane and Gallium Crystallization in Hydrodynamic Czochralski Model.
Prostomolotov, Anatoly Ivanovich
S05-P06 - Growth of large size YAG:Ce crystals with homogenous distribution of Ce3+ ions by HDC method for WLED application.
Nizhankovskyi, Sergii Victorovich
S05-P07 - The approach for reconstruction of GaSb:Te space crystal growing.
Prostomolotov, Anatoly Ivanovich
S05-P08 - Influence of melt transparency on critical growth rate of sapphire.
Baranov, Viacheslav
S05-P09 - Growth of high optical quality ZnS single crystals by solid phase recrystallization technique at barothermal treatment.
Avetisov, Roman
S05-P10 - Sapphire Shaped Crystals for Medicine.
Shikunova, Irina
S05-P11 - Salt stains from evaporating droplets.
Shahidzadeh, Noushine
S05-P12 - Crystal growth under high electric field: Analysis of the nucleation process.
Hicher, Patrick
6 - Mesocrystals and Nonclassical Crystallisation ⁄ Growth of Biological Materials and Biologically-Controlled Growth
S06-P01 - An Approach for Controlling Epitaxial Growth of Protein Crystal by Using Microfluidic Device.
Maeki, Masatoshi
S06-P02 - Biogenic and non-biogenic struvite.
Prywer, Jolanta
S06-P03 - Influence of tetrasodium pyrophosphate on struvite and carbonate apatite formation.
Olszynski, Marcin
S06-P04 - Investigation of bacterial factors responsible for aggregation process of carbonate apatite.
Sadowski, Rafal Robert
S06-P06 - Prenucleation clusters - quatarons - and crystal growth.
Askhabov, Askhab Magomedovich
7 - In-situ Monitoring ⁄ Control of Crystal Growth Processes ⁄ Crystal morphology
S07-P03 - Development of in-situ observation system for high-temperature liquid/solid interfaces: application to solid-source solution
growth of AlN.
Kangawa, Yoshihiro
S07-P06 - Peculiarities of sapphire nitridation under the influence of the high-energy electron beam.
Milakhin, Denis Sergeevich
S07-P07 - Using modifiers to mitigate salt crystallization damage in porous building materials: an optical microscopy study of borax
and sodium sulphate.
Granneman, Sanne
S07-P08 - Optimization of Cooling Crystallization of High Aspect Ratio Crystals in Batch and Continuous Operations for Size and
Shape Control.
Acevedo, David
S07-P10 - Nanoconfined Crystal Growth investigated by Reflection Interference Contrast Microscopy.
Kohler, Felix
S07-P12 - Microfluidics for in situ study of growth of calcium carbonate.
Li, Lei
S07-P13 - In-situ Raman technique applied to monitoring phase transition of linear alkylbenzene sulphonate (LAS).
Zou, Boyang
S07-P14 - Solubility studies of GaN in NH3/mineralizer-solutions.
Steigerwald, Thomas Gottfried
S07-P15 - Analysis of temperature data obtained by measurements of temperature field at simulated vertical Bridgman crystal
growth of PbCl2.
Kral, Robert
S07-P16 - Controlling Ice Growth using Selective Infrared Radiation.
Guy, Shlomit
S07-P17 - Electron Microscopy Studies of Growth and Structure of MoS2-based Hydrodesulfurization Catalysts.
Hansen, Lars Pilsgaard
8 - Epitaxial Growth - Crystal Growth Interfaces
S08-P01 - Impact of boron on the step-free area formation during molecular beam epitaxial growth on MESA structures on Si(111)
Roy Chaudhuri, Ayan
S08-P02 - Semipolar AlN and GaN on Si(100): concept, HVPE technology and layer properties.
Konenkova, Elena Vasilievna
S08-P03 - Structure of AlN layer obtained by thermochemical nitriding of (0001) sapphire substrate with terrace-step surface.
Vovk, Olena Olexandrivna
S08-P04 - Growth of α-Cr2O3 thin films on α-Al2O3 substrate at low temperature by r.f. magnetron sputtering.
Gao, Yin
S08-P05 - n-i-p triple junction obtained by the Atomic Layer Deposition method.
Gieraltowska, Sylwia
S08-P06 - 2D-islands Nucleation on Si(111) at High Temperature During Sublimation and Thermal Etching by O2.
Sitnikov, Sergey
S08-P07 - β-Ga2O3 crystal deposition on sapphire and silicon substrates by chemical assisted vapor transport method.
Pechnikov, Aleksei
S08-P08 - Dependence of the relaxation of elastic stress on the sign of strain in SiGe epitaxial layers.
Novikov, Alexey
S08-P10 - Influence of thermal treatment on the optical and electrical properties of ZnO:B thin films.
Gritsenko, Lesya Vladimirovna
S08-P11 - Preparation and optimization of a molybdenum electrode for CIGS solar cell.
Feng, Jingxue
S08-P12 - Surface induced weak orientational order and role of isotropic nematic-interface fluctuations in the appearance of an
induced nematic film.
Pikina, Elena
S08-P13 - Effects of thermal annealing on AlInGaN/AlN/GaN heterostructure grown by MOCVD.
Ravi, Loganathan
S08-P16 - Growth and Optical Investigation on InGaN/GaN Quantum well Structures grown by Metal Organic Chemical Vapour
Deposition.
Kandasamy, Prabakaran
S08-P17 - Synthesis and thin films growth of BaBiO3, Ba1-xKxBiO3 and BaBiO1-yFz compounds by pulsed laser deposition.
Gawryluk, Dariusz Jakub
S08-P18 - Properties of Crystalline Silicon Layers for Photovoltaic Application grown on Glass by Steady-State Solution Growth.
Ehlers, Christian
S08-P19 - CdHgTe deposited on CdZnTe substrates by Closed Space Sublimation technique.
Rubio, Sandra
S08-P22 - Growth and luminescent properties of single crystalline films of Ce3+ doped Gd1-xLuxAlO3 and Pr1-xLuxAlO3 perovskites.
Zorenko Yuriy
S08-P25 - Strained Ge layers on virtual Si(1-x)Ge(x)(001) substrates.
Schmidt, Jan
S08-P26 - Reconstruction phase transition c(4x4) - (1x3) on the (001)InSb surface.
Bakarov, Askhat
9 - Fundamentals - Structural Defects and their characterization in Crystalline Materials
S09-P03 - Study of charge compensating defects in BaF2:YbF3 crystals using dielectric relaxation”
Octavian Bunoiu
S09-P04 - "Some optical properties of YbF3 doped BaF2 crystals"
Octavian Bunoiu
S09-P05 - Interplay mechanism of secondary phase particles and the extended dislocations in CdZnTe crystals.
Xu, Yadong
S09-P06 - Oxygen precipitation behavior in heavily arsenic doped silicon crystals.
Porrini, Maria
S09-P07 - Blocks and Residual Stresses in Shaped Sapphire Single Crystals.
Grigorievich, Nosov Yuri
S09-P08. Strain Energy Analysis of Screw Dislocations in 4H-SiC by Molecular Dynamics.
Kawamura, Takahiro
S09-P09 - Study of defect formation in KDP crystals under high supersaturation.
Baskakova, Svetlana Sergeevna
S09-P10 - Czochralski growth and characterization of rare earth-doped Gd3(Al,Ga)5O12 crystals.
Ryba-Romanowski, Witold
S09-P11 - Nonstoichiometry and luminescent properties of ZnSe crystals grown from the melt at high pressures.
Avetissov, Igor
S09-P12 - Nonstoichiometry and luminescent properties of tris(8-hydroxyquinoline)aluminum crystals.
Avetisov, Roman
S09-P13 - Two-dimensional thermoluminescence method for checking crystals homogeneity.
Marczewska, Barbara
S09-P14 - Disorder control of nanostructural arrangement in AlGaN/GaN light-emitting structures and related phenomena.
Shabunina, Evgeniia
S09-P15 - Effect of gamma irradiation on the optical properties of CVT grown ZnSe single crystals.
Perumal, Kannappan
S09-P16 - Thermal stability of ferroelectric domain gratings in Rb-doped KTP.
Peña Revellez, Alexandra
S09-P17 - Argon ion irradiation effects on CdZnTe crystals: influence of the substrate temperature.
Plaza, Jose Luis
S09-P18 - On Defects Detection in Crystals using Image Processing and Pattern Recognition Tools.
Porat, Moshe
S09-P22 - Mystical source of electrically active chlorine at Cl doped CdTe.
Sedivy, Lukas
S09-P23 - Structural examination of multilayer CrAlN/AlSiN films.
Polychroniadis, Efstathios K.
S09-P26 - Dislocation mechanism of KDP growth from solution.
Alexandru, Horia V.
10 - Nanostructures & Nanoporous Crystals
S10-P01 - Vapour phase catalyst-free growth of β-Ga2O3 nanowires.
Calestani, Davide
S10-P03 - Bioceramic Coatings Produced on Commercially Pure Titanium by the Induction Heat Treatment and Nanostructure
Surface Modification.
Fomin, Aleksandr
S10-P04 - Metal-Oxide Coatings with Ultrafine Crystalline Structure on Medical Implants Fabricated from Stainless Steel.
Fomin, Aleksandr
S10-P07 - Growth Mechanism of ZnO Films by Non-vacuum Process at Low Temperature.
Yoshino, Kenji
S10-P08 - Low Temperature Growth of Ga-doped ZnO Thin Films Grown by Atmospheric Spray Pyrolysis for CuInGaSe2 Based
Solar Cells.
Yoshino, Kenji
S10-P10 - Nitride-based self-assembled magnetic nanocrystals and complexes.
Capuzzo, Giulia
S10-P11 - Growth and Formation of Nanostructures on Metal Surfaces under the Action of Nanosecond Laser Pulses.
Mikolutskiy, Sergey Ivanovich
S10-P13 - The influence of V/III flow ratio on the self-induced InAs nanowires growth.
Sibirev, Nickolay Vladimirovich
S10-P14 - Growth and characteristics of InAlAs/AlGaAs quantum dots depending on annealing temperatures.
Han, Il Ki
S10-P15 - GaN-ZnO Solid solution for photocatalytic applications : Synthesis by Solution Combustion technique and
characterization.
Menon, Sumithra Sivadas
S10-P16 - Cu Catalytic Growth of GaN Nanowires on Sapphire Substrate for p-type behaviour.
Kuppulingam, Boopathi
S10-P18 - Precursors for CIGSe micro-concentrator solar cells.
Eylers, Katharina
S10-P19 - Effect of ZnO/B2O3 ratio on the crystal growth in zinc borosilicate glasses.
Kullberg, Ana Teresa
S10-P20 - Synthesis and Characterization of HgI2 Nanostructures for Films Nucleation.
Fornaro, Laura
S10-P21 - Synthesis and investigation of hexagonal modification NaY1-x-yYbxEryF4.
Mayakova, Mariya Nikolaevna
S10-P22 - Hydrothermally Grown Arrays of ZnO Nanorods on Patterned Substrates.
Grym, Jan
S10-P23 - Synthesis of BiI3 nanoparticles through hydrothermal method intended for preparing ionizing radiation detectors.
Fornaro, Laura
S10-P24 - HgS nanostructures for the development of hybrid active layers.
Fornaro, Laura
S10-P25 - Growth of ZnO nanorods on carbon fibers for in-situ stress measurements.
Culiolo, Maurizio
S10-P29 - Mass-transport driven growth dynamics of AlGaAs shells deposited by metalorganic vapor phase epitaxy around dense
GaAs nanowire ensembles
Lovergine Nico
S10-P30 - Laser processed oxides for optoelectronics and bio applications.
Costa, Florinda Mendes
S10-P31 - Obtaining of II-VI compound single crystal substrates with controlled electrical properties and prospects of their application
for manufacturing nanotemplates.
Colibaba, Gleb V
S10-P32 - Surface Morphological Analysis of nano-patterned c-plane sapphire substrates using 450KeV oxygen ions.
Jacob, Davis
S10-P33 - Surface modification of Cu2O/p-CuxS thin films for Liquefied Petroleum Gas sensing.
Bandara, Kiriwithanage Nayana
11 - Novel Materials and Structures
S11-P02 - Growth of p-type ZnOS films by pulsed laser deposition.
Kobayashi, Kenkichiro
S11-P04 - On the crystal growth, characterization and magnetic properties of two new phases discovered in the PbO-Fe2O3-P2O5
system.
Velazquez, Matias
S11-P05 - Synthesis and structure of perovskite organic-inorganic hybrid of [NH3(CH2)4NH3CoCl4] 1,4 butane diammonium
tetrachlorocobaltate.
Abdel-aal, Seham Kamal
S11-P07 - Macro- and microcrystallization of rare-earth aluminum borates in multicomponent systems RAl3(BO3)4 - K2Mo3O10 - B2O3
- R2O3 (R = Y, Gd, Lu).
Naprasnikov, Daniil Alekseevich
S11-P09 - Structural Characterization of Cobalt Oxide Core-Shell Nanostructure.
Lukic-Petrovic, Svetlana
S11-P11 - Low Temperature Growth of Cu2ZnSnS4 Thin Films by Metal Xanthate Precursors.
Yoshino, Kenji
S11-P12 - Formation of microcrystalline SrB4O7 :Sm2+ dots in SBO glass-ceramic.
Glowacki, Michal Marcin
S11-P13 - Form Studies and Thermodynamic Evaluation of Fasoracetam.
Harmsen, Bram
S11-P15 - Crystal and electronic structure and magnetic properties of Gd7Pd3 xNix intermetallics.
Talik, Ewa
S11-P16 - New fluorescent hybrid materials in oxyfluoride glass matrix.
Avetisov, Roman
S11-P17 - Crystal engineering of molecular salts for single-crystal to single-crystal [2+2] cycloaddition photoreactions.
Spinelli, Floriana
S11-P18 - Crystallization of a New Calcium Bisphosphonate through Octacalcium Phosphate Digestion.
Boanini, Elisa
S11-P19 - X-Ray diffraction and Raman spectroscopy studies of temperature induced phase transitions in Sr3-xCaxFe2TeO9 (0 ≤x≤ 1)
triple perovskite.
Elhachmi, Abdelhadi
S11-P20 - Growth and structure of single crystal Ba3TaFe3Si2O14 -langasite family multiferroics.
Balbashov, Anatoly
S11-P22 - Large GaPd2 single crystals grown by the Czochralski technique.
Schwerin, Judith
S11-P23 - Synthesis and crystal growth of NdAl3(BO3)4 with different polytypic structures.
Volkova, Elena
S11-P24 - 2D transition metal dichalcogenides grown by chloride driven chemical vapor transport.
Barreteau, Celine
S11-P26 - Influence of polyols on the formation of nanocrystalline nickel ferrite inside silica matrices.
Bunoiu, Octavian Madalin
S11-P31 - Growth and stability of pinacol hydrates.
Sobczak, Szymon
S11-P33 - High pressure High temperature (HP / HT) growth of multifunctional perovskites. How chemical substitutions can be used
to switch from a magnetoresistive to a dielectric (polar) magnet.
Delmonte, Davide
ABSTRACTS
SESSION 1
Fundamentals of Nucleation and Growth Kinetics
Numerical Modelling of Liquid Phase Diffusion growth of SiGe with Uniform
Compositions
S. Dost1, M. Sakhon, N. Armour
Crystal Growth Laboratory, University of Victoria, Victoria, BC Canada V8W 3P6
Liquid Phase Diffusion (LPD) is a solution growth technique that was developed as a variant of
multicomponent zone melting growth [1]. This technique, where was called “LPD”, was then utilized by
[2,3] to grow graded bulk crystals from the germanium side with the objectives of producing seed crystals of
desired composition for other growth techniques such as Czochralski and Liquid Phase Electroepitaxy
(LPEE). Recently research has been extended where the effects of rotating and static magnetic fields on the
transport process were also investigated [4,5]. In these previous studies the LPD growth system was
stationary and was subject to an applied temperature gradient. The driving force for growth was the
supercooling of the melt due to dissolution of silicon into the germanium melt. Crystals of SiGe were grown
with increasing silicon composition along the growth direction. Silicon compositions in the radial direction
were uniform.
In the present study, we have carried out new LPD experiments by applying a crucible translation matching with that the
solidification rate in order to grow crystals at desired uniform compositions. Determination of optimum translation rate is
the issue. In order to shed light into the LPD growth process further we have also carried out numerical simulations of
the system. Both constant and dynamic translation rates have been considered. A top-level code is developed in
OpenFOAM using a fixed grid approach to model the complete growth process. The process has been simulated by
prescribing dynamic thermal boundary conditions along the growth configuration. The numerical solution also reveals a
significant reduction in the axial composition gradient in the grown crystal with an additional advantage of shorter growth
periods justifying the use of crucible translation as a means to achieve higher compositional uniformity in the grown
crystals. Numerical simulations were also carried out, using the commercial code “Fluent”, to examine the benefit of
crucible rotation for obtaining better mixing and also for suppressing the initially strong convective flow in the melt.
Results showed that a rotation in order of 20 rpm is optimum.
1. Y. Azuma, N. Usami, T. Ujihara, G. Sazaki, Y.Murakami, S. Miyashita, K. Fijiwara, K. Nakajima, J.
Crystal Growth, 224 (2001) 204.
2. M. Yildiz, S. Dost, B. Lent, J. Crystal growth, 280 (2005) 151-160.
3. Yildiz, M., S. Dost, and B. Lent, Cryst. Res. Technol., 41(3) (2006) 211-216.
4. Armour, N., and S. Dost, Cryst. Res. Technol., 45(3), 244-248, 2010.
5. Armour N., and S. Dost, Cryst. Res. Technol., 45(4), 335-340, 2010.
1
Corresponding author: [email protected] An in situ view of nucleation
De Yoreo, James J.*1, Ma, Xiang1, Nielsen, Michael H.2, Chen, Chun-Long1
11
Pacific Northwest National Laboratory, Richland, WA 99352, USA
Department of Materials Science and Engineering, Univ. of California, Berkeley, 94720 USA
*email: [email protected]
22
In the classical picture of nucleation, density fluctuations that are inherent at finite temperature
form unstable clusters of the new phase through monomer-by-monomer addition. Clusters
transition from being unstable to stable if they exceed a critical size, beyond which the free energy
cost of creating the new phase boundary is compensated by the drop in chemical potential. In
recent years, hierarchical pathways involving assembly of species more complex than monomers
have been proposed for numerous systems. Amongst these, a “two-step nucleation” process was
proposed whereby crystals of proteins, other macromolecules, and even simple salts nucleate within
monomer-rich, non-crystalline clusters. However, reports of such pathways are almost entirely
based on computational models or interpretations of indirect observations. Moreover, little is
known about two-step nucleation dynamics and whether the monomers in the clusters are one and
the same as those that comprise the crystal nucleus or are act instead to provide an environment for
heterogeneous nucleation is uncertain, as is the extent to which these multistep pathways are
general features of either macromolecular or inorganic materials. To address these knowledge gaps,
we have used in situ TEM and AFM to investigate nucleation in a number of systems.
To examine nucleation pathways of macromolecules, we synthesized a biomimetic polymer
sequence that forms 2D ordered structures and used in situ AFM to observe nucleation. Our results
show that the nucleation occurs along a two-step pathway that begins with creation of disordered
clusters containing ~ 10-20 molecules. These clusters transform directly into ordered nuclei that
grow via molecule-by-molecule addition, with the kinetics of transformation strongly dependent on
Ca2+ concentration. However, when a small aggregation-promoting hydrophobic region is deleted,
even though the same final structure is obtained, nucleation occurs in a single step and the
nucleation kinetics are dramatically altered.
To investigate nucleation of simple inorganic materials, we used in situ TEM to observe
nucleation of CaCO3. [1] Formation pathways are confirmed in most cases by collecting diffraction
information of the observed phases. We find that amorphous calcium carbonate (ACC), as well as
the three predominant crystalline phases: calcite, vaterite, and aragonite, can form directly even
under conditions in which ACC readily forms. In addition to these direct formation pathways, we
observe two-step nucleation of aragonite and vaterite from ACC. Here, ACC transforms directly to
the crystalline phases through distinct nucleation events on or just beneath the surface followed by
consumption of the parent ACC particle.
The results demonstrate that two-step pathways are possible in both inorganic and
macromolecular systems, but are not universal. They can be accompanied by direct nucleation
pathways and, in the case of macromolecules, their existence can depend on the specific sequence
of the molecule.
References:
[1] Nielsen M.H., Aloni, S., De Yoreo, J.J., Science, 345 (2014) 1158.
Homogeneous nucleation in small droplets near critical supercooling
Zdeněk Kožíšek*, Pavel Demo
Institute of Physics of the Czech Academy of Sciences, Cukrovarická 10, 162 00 Praha 6 (Czech Republic)
8
7
6
5
4
3
2
1
0
8
a
-6
7
10
-9
10
-12
10
0
0.1
0.2
t (s)
rmax (nm)
r (nm)
Within standard nucleation model the kinetic equations are numerically solved to determine the
size distribution of nuclei in small volumes near critical supersaturation, when first nuclei are
formed. The size distribution of clusters, F, in small volumes reaches the stationary value after
some time delay and decreases with cluster size i. Supercritical clusters are called nuclei. The size
of the largest nucleus i was determined from the condition Fi=1. As a model system we selected
recently studied liquid-to-crystal transition in Ni [1] due to available experimental and simulation
data. However, using these data leads to the size distribution of nuclei, when no critical nuclei in Ni
sample masses from 23 µg up to 63 mg are formed (number of critical nuclei < 1). From this point
of view one needs to consider lower interfacial energy σ or to consider the size dependence of σ to
increase number of critical nuclei to reasonable level.
In larger volume (V=10-9 m3) the radius of the largest nucleus within system r increases with
time, but at lower volumes (V=10-9 and 10-12 m3) nucleus size reaches some extremal size rmax at
relative supercooling (TE-T)/TE=0.171, where TE denotes melting temperature (Fig. 1a). This limit
of maximum size rmax quickly increases with relative supercooling (Fig. 1b).
Critical supersaturation, when first nuclei are detected within system, and also maximum size of
nuclei formed within system, depend on the droplet volume. Supercritical clusters continue in their
growth only if the number of critical nuclei is sufficiently high. Moreover, in very small volumes
nucleation kinetics differs from standard model due to depletion of the parent phase [2].
This work was supported by the Grant No. P108/12/0891 of the Czech Science Foundation.
b
6
5
4
3
2
1
0.16
10-9
0.17
0.18
(TE-T)/TE
10-12
0.19
Figure 1. Radius of the largest formed nucleus r as a function of time t (a) and relative supercooling
(TE-T)/TE (b) for volumes V=10-6, 10-9, and 10-12 m3.
References:
[1] Bokeloh J., Rozas R. E., Wilde G., Phys. Rev. Lett., 107 (2011) 145701.
[2] Kožíšek Z., CrystEngComm, 15 (2013) 2269.
Separation of nucleation and growth stages - a way for studying crystal nucleation
kinetics and to rule a crystallization process designed to reduce crystal polydispersity
Nanev Christo N.*, Tonchev Vesselin D.
e-mail: [email protected]
Rostislaw Kaischew Institute of Physical Chemistry, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria
Although very simple, the classical nucleation-growth-separation principle, NGSP provides a unique
possibility for a direct nucleation study - without ever actually seeing the nuclei themselves: Initially, one
rapidly supersaturates a system so that nucleation occurs. To avoid the growth of the arising nuclei, the
nucleation period is short. The NGSP was devised due to the principle impossibility to observe elementary
acts of crystal nucleation, which proceed at a molecular scale. Therefore, to make nucleated crystallites visible
under light microscope the nucleation process is abruptly stopped and the created nuclei are let to grow. This
is achieved by rapidly lowering the supersaturation below the upper limit of the metastable zone, i.e. below the
threshold limiting the crystal nucleation process. Depriving the system of its capability to further produce
nuclei, only the existing super-critically sized clusters are let grow to microscopically visible crystals.
Originally, NGSP found application in studying crystal nucleation kinetics: counting the crystals, and
plotting their number density, n vs the nucleation time, t, the stationary nucleation rate for the corresponding
supersaturation is determined from the linear parts of the curves. Recently, NGSP’s application was
broadened; it was used to rule a crystallization process designed to reduce crystal polydispersity, Fig. 1; an
internal crystal “seeding” leads to nearly-uniform size insulin crystals, but only after relatively short growth
times, till 1 day [1]. With prolonged growth the size scatter augments, despite equally sized crystal “seeds” and
the same outer conditions are used. Detailed consideration is given on the inherent trend for increasing
polydispersity, in which the emphasis is put on the presence of more active step sources on some of the
crystals. Size distributions of the insulin crystals are interpreted retrospectively to give clues concerning the
nucleation process itself.
Figure 1. Rhombohedral insulin crystals grown without applying NGSP, and with applying it.
Reference:
[1] Nanev C.N., Tonchev V.D., Hodzhaoglu F.V., J. Cryst. Growth 375 (2013) 10-15.
Beams and Blocky Crystals: Another Challenge from the Naica Giant Crystals
Fermín Otálora1*, Joaquín Criado1, Juan-Manuel Garcia-Ruiz1
1
Laboratorio de Estudios Cristalográficos. IACT, CSIC/Ugr.
Av. Las Palmeras 4, Armilla 18100, Granada (España)
The giant gypsum crystals discovered in 2000 in Naica (Mexico) have been since them a source
of deep fascination not only because of their spectacular size and look, but also due to the wealth of
scientific information that the mineralogical/crystallographic community has got from them. After
14 years of study, [1] one question was still missing in this list of scientific advances triggered by
the giant Naica crystals: the origin of two clearly distinct crystal habits for gypsum in the Cave of
Crystals, bulky crystals with a morphology close to the equilibrium one [2] or much longer crystals,
called “beams”, up to 11 meters long.
The coexistence of these two habits so widely different is explained in this communication by a
growth rate enhancement at a re-entrant twin angle, where the surface at the atomic scale shows
positions similar to growth steps. These positions operate as a source of growth steps additional to
any other mechanism, changing the relative growth rate, accelerating the growth of the faces
meeting at the reentrant angle and modifying the habit of the twinned crystal [3].
Giant beams in Naica are shown to be 100 contact twins with reentrant twin angles (figure 1a)
but the extremely low supersaturation at which the Naica crystals grew makes impossible the
laboratory replication of the conditions. The same twins were obtained at higher supersaturation and
their growth kinetics analyzed. In these twinned crystals, we checked for the re-entrant angle
mechanism as the origin of the elongation of gypsum beams. Figure 1b and c show two sample
gypsum crystals growing at the reentrant angle of the 100 contact twin. Figure 1d shows the growth
rate measured for the convex and concave sides of the twin, and the growth rate acceleration by a
factor of 10 to 30 that results in an elongated habit for these twinned crystals, as proposed for the
Naica giant beams.
Figure 1. The 100 contact twin geometry sketch and a giant Naica Beam showing it (a). Two twinned
gypsum crystals growing by reentrant angle growth rate enhancement (b) and (c). The growth rate
of the convex (solid squares) and concave (open circles) ends of crystal 1b is shown in (c).
References:
[1] Otálora, F. and García-Ruiz, J.M. Chem Soc Rev. 43, (2013) 2013
[2] Massaro, F.R., Rubbo, M. and Aquilano, D. Crystal Growth & Design, 10 (2010) 2870
[3] Kitamura, M., Hosoya, S. and Sunagawa, I. J. Crystal Growth, 47 (1979) 93
Origin of energy efficiency of axial vibration
control technique in melt growth process
Evgeny Zharikov, Andrey Sadovskiy, Ekaterina Sukhanova, Vladimir Kostikov, Igor Avetissov*
D. Mendeleyev University of Chemical Technology of Russia, Miusskaya pl. 9, Moscow (Russia)
The problem of the effective heat-mass transfer in melt-crystal growth technologies plays a
significant role in production of high quality crystals. It was demonstrated that the axial vibrational
control technique [1] is one of the most energy efficient technique to manage the melt flows at
growth process and govern crystal perfection [2]. The energy induced into the melt by low
frequency oscillation of an inert solid baffle (commonly in the form of a disk) could be as high as
hundreds joules per mole in a nanosize volume near the disk sharp edge. The melt microstructure
evolution under the action of the low-frequency axial vibration control (AVC) technique was
studied in situ by Raman spectroscopy and proved by DTA, HT-XRD, DSC measurements [3]. A
number of vibrational effects, such as increase of permissible growth rate, distinct alteration of
crystallization heat, significant reduction of dislocation density and others are connected with AVC
influence on pre-crystallization phenomena and destruction/reconstruction of clusters in the melt at
temperatures close to the melting point.
In the present research we analyzed the energy efficiency of AVC impact on melt growth
process. Fig. 1 demonstrates the influence of the oscillating baffle configuration on the energy
induced into the various melts (NaNO3, Ge, CdTe) which significantly differ in viscosity, density,
thermal conductivity and specific heat. It was recognized that the disk sharp edge curvature strongly
influenced on the induced energy. The numerical simulation was conducted using ANSYS
FLUENT 14.5 software and the UDF realizing the disk harmonic oscillation.
Figure 1. Numerical simulation of momentum viscous dissipation in NaNO3 melt activated by
oscillation (f=25 Hz, A=0.3 mm) of cylindrical disc with different curvature (R) of a sharp edge
The research was supported by the Russian Foundation for Basic Research grant 13-02-12199.
References:
[1] Zharikov E., In: Crystal growth technology. Semiconductors and dielectrics. (Capper P., Rudolph P.,
eds.), Weinheim: Wiley-VCH Verlag; 2010, p. 41-64
[2] Avetissov I., et. al., CrystEngComm. 15 (2013) 2213
[3] Sadovskiy A., et. al., J. Crystal Growth 417 (2015) 16
Growth of branched rutile-type TiO2 via self-assembly and crystal twinning
Jordan Vanja*1,2, Rečnik Aleksander 1
1
Department for Nanostructured Materials, Jožef Stefan Institute, Jamova cesta 39, Ljubljana (Slovenia)
2
Jožef Stefan International Postgraduate School, Jamova cesta 39, Ljubljana (Slovenia)
Nowadays, mainstream of research in materials science is focused on the novel approaches to
synthesize highly branched 3D materials with increased capacity, adaptable morphology, large
specific surface area and surface properties tailored for diverse applications [1]. One of the main
challenges is understanding crystal nucleation and growth mechanisms, thereby to gain the control
for producing desirable branched fractal-like structures (length, width, control of branching events,
etc.). With this in mind we focused on studying the most important reaction parameters, including
the reaction temperature, precursor and reagent concentration in hydrothermal (HT) synthesis of
rutile TiO2. Precursor concentration in the reaction medium (defined as a volume ratio between
Ti(IV)-butoxide precursor and HCl: XV) has proved to be the most relevant reaction parameter that
influences the nucleation rate and hence the branching of rutile. The highest branching is achieved
at the highest XV of 1:33, leading to the formation of rutile microspheres consisted of numerous
ultrafine rutile fibers radiating from the common center (Fig.1a), however when XV is decreased to
1:100 the products show fewer but more defined branches where numerous twin incidences and
other types of intergrowths can be observed (Fig.1b). High resolution transmission electron
microscopy (HRTEM) revealed that the final crystals are growing through the attachment of about
4-5nm thick rutile fibers (Fig.1c) aggregated along {110} planes, with occasional attachments by
{101} planes, causing the formation of {101} twins. Twinning relations were confirmed by the
selected area electron diffraction across the twin contacts. In crystals oriented in [001]R projection
the inherent porous texture can be observed due to imperfect alignment of fibers. On the basis of
our experimental results, we propose that the growth mechanism of these highly branched structures
is based on crystal aggregation, i.e. self-assembly and more rarely – twinning. Their growth can be
divided into three stages: (i) formation of Ti-complexes in the reaction solution, leading to burst
nucleation of long rutile fibers when supersaturation is reached (Fig.1c), (ii) aggregation of fibers
along {110} and {101} planes through dehydration reactions to form rutile crystals, and (iii)
recrystallization that dissolves small nuclei.
Figure 1. (a) Fast nucleation rate when XV is set to 1:33, leads to the formation of highly branched
microspheres. (b) With the decrease of XV to 1:100 nucleation rate is slowed down, leading to more perfect
attachments during fiber aggregation. Rutile crystals were HT obtained in 7M HCl at 180°C for 3h. (c)
HRTEM of rutile fibers roughly aligned along their crystallographic c-axis
References:
[1] Cheng C., Fan H.J., Nano Today, 7 (2012) 327-343.
Selective crystallisation of the more stable β polymorph of L-glutamic acid in an
acoustic levitator
Rusin Michal1, Ristic Radoljub*1, Gnutzmann Tanja2, Emmerling Franziska2
1
Department of Chemical and Biological Engineering, The University of Sheffield, Mappin Street, Sheffield S1 3JD, UK
BAM Federal Institute for Materials Research and Testing, Richard-Willstaetter-Strasse 11, 12489 Berlin, Germany
2
We observe the nucleation and growth phenomena accompanying the crystallisation of Lglutamic acid (LGA) from its pure solution droplet suspended in an acoustic levitator – an open
thermodynamic system. For this purpose, in-situ simultaneous WAXS, Raman spectroscopy and
droplet size monitoring techniques were used [1]. Here, we demonstrate, for the first time, that these
containerless conditions lead to the nucleation of only stable β form. These observations further
demonstrate the sensitivity of crystal nucleation to droplet-air interface structure, the potential of
this kind of interface for controlling polymorphism and discovering new polymorphs. In order to
get some insight into the above polymorph selection, we compare the subsequent time dependent
mole fraction evolutions of the crystallising monomorphic β and dissolved LGA (Fig 1a) with those
for dimorphic, typical for closed thermodynamic systems such as batch crystalliser (Fig 1b).
(a)
(b)
Figure 1. (a) Mole fraction evolutions in an open thermodynamic system (a levitating droplet) of the
selected β phase and dissolved L-glutamic acid (red – β, green – L-glutamic acid in solution). (b)
Mole fraction evolutions in a closed thermodynamic system (a butch crystalliser) of the crystallising
phases and dissolved L-glutamic acid determined for pure solution (blue – α, red – β, green – Lglutamic acid in solution)
References:
[1] Klimakow, M., Leiterer, J., Kneipp, J., Rossler, E., Panne, U., Rademann, K. & Emmerling, F.,
Langmuir, 26, 11233-11237, 2010.
Enhanced Crystallization Efficiency of an Active Pharmaceutical Ingredient
through the Formation of Micron-Sized Crystals in the Undersaturated State.
Bart Rimez*1, Edith Norrant2, Benoît Haut1, Benoit Scheid1
1
Université Libre de Bruxelles - Transfers, Interfaces and Processes (ULB-TIPs), Avenue F.D. Roosevelt 50, 1050
Brussels (Belgium)
2
UCB BIOPharma SPRL, Chemin du Foriest, 1420 Braine L’Alleud (Belgium)
*email:[email protected]
Particle sedimentations were found in solutions of an Active Pharmaceutical Ingredient (API)
and several organic solvents like Methyl Isobutyl Ketone (MIBK), IsoPropyl Acetate (IPAC) and
water, seemingly independent of the total solute concentration. Several different analysis techniques
pointed out that these particles are formed at temperatures beyond solubility, albeit disappear above
the melting temperature of the pure compound (80°C). Dynamic Light Scattering (DLS) tests have
shown that these particles can be filtered out of the solutions, after which a new sedimentation takes
place. Upon evaluation of these filters after drying, it became clear that the particles do not only
consist of API molecules, they are crystalline and have sizes ranging between 1 to 30 m. A SEM
image of these particles deposited on a polypropylene filter is shown in figure 1. X-Ray Diffraction
experiments showed that the found particles have an identical crystal lattice to the pure API
compound in its desired crystal morphology, which is of the cubic type.
These findings lead to the development of a fast and efficient way to crystallize this API in the
desired crystal form, using microfluidics in the present study. In fact, crystallization will only occur
after isothermal treatments in between the solubility line and the melting temperature of the pure
API, crystal growth follows then immediately after reaching supersaturated conditions. Depending
on experimental conditions, single to multiple cubic crystals can be formed inside microfluidic
droplets within short timeframes, discriminating the undesired needle crystals, kinetically more
favorable, in favor of the cubic ones [1].
Figure 1. Scanning Electron Microscope image taken of the particle sediment deposited onto a PP filter and dried
subsequently.
References:
[1] Rimez B., Haut B, Scheid B, Proceedings of the 21st International Workshop on Industrial
Crystallization (BIWIC), 2014.
POSTER
S01-P02
Experimental research of phase transitions in a liquid melt of high-purity
aluminum
V.B.Vorontsov, V.K.Pershin, M.S.Udintseva
This scientific work is developed to the studying of the genetic connection
structures of solid and liquid phases.
Based on the results of previous studies [1, 2] cluster formations in the melt the micro-regions, those retain crystallinity (areas with short-range order of
symmetry) were considered as the sours of AE.
Fourier analysis of signals of acoustic emission (AE) accompanying melting
high purity aluminum from the melting point up to t=860 degrees Celsius was
performed.
The experimental data allowed to follow the dynamics of disorder zones range
order in the melt with increasing melt temperature up to their complete destruction.
The presented results of spectral analysis of the signals were analyzed from the
standpoint of the theory of cluster melting metals.
Reference
1. V.B.Vorontsov and V.V.Ktalnikov Analysis of acustic emission accompanying
metal crystallization: Journal of fhysics, 2008.-p.1-9
2. V.B. Vorontsov, D.V.Zhuravlev, J.Chem.Chem.Eng.6 (2012) 358-362.
3. O.B. Sokolov, l.A.Ugodnikova, Transformation an Fourier Series .In Textbook
of metodic, Ekaterinburg, 2005.
4. Aluminum Crystals: experimental Results and Theoretical Model of the
Cluster: Journal of Chemistry and Chemical Enginnering, ISSN 1934, USA,
6(2012) 358-362, 20123 j.
S01-P03
On the Theory of Ostwald Ripening: Formation of the Universal Distribution
Function in the Presence of Different Mass Transfer Mechanisms
Dmitri Alexandrov*1
1
Laboratory of Multi-Scale Mathematical Modelling, Department of Mathematical Physics, Ural Federal University,
620000, Ekaterinburg (Russian Federation)
A theoretical description of the concluding stage of Ostwald ripening given by Lifshitz and
Slyozov (LS) in the case of diffusion-limited crystal growth [1, 2] and by Wagner [3] in the case of
interface-limited growth predicts that after long times the distribution of particles over sizes tends to
a universal form. A qualitative behavior of their theory has been confirmed, but experimental
particle size distributions are more broad and squat than the classical asymptotic solutions [4].
The origin of discrepancies between the theory and experimental data is caused by the
formation and relaxation of solutions from the early to late stages of Ostwald ripening. In other
words, the initial conditions at the ripening stage lead to the formation of a transition region near the
blocking point of the classical theory and completely determine the distribution function. A new
analytical approach developed here on the basis of recently developed theory [5] focuses on the
formation process and relaxation dynamics of analytical solutions from the early stage of Ostwald
ripening to its concluding state, which is described by the classical asymptotic solutions. An
algebraic equation for the boundaries of a transition layer independent of all material parameters is
derived. A time-dependent function responsible for the evolution of solutions at the ripening stage
is found in the case of different mass transfer mechanisms. Two cases of power-depended and
exponentially decaying initial cluster-size distributions are considered. The distribution function
obtained is more broad and flat than the classical asymptotic solutions. The analytical solutions
obtained are in good agreement with experimental data (figure 1).
Figure 1. The size distribution function P(u) is compared with 20 year experiments [4] (u is the
dimensionless size of particles). The solid line shows the LS asymptotic solution whereas the dashed
and dotted lines demonstrate the theory under consideration in the case of volume diffusion mass
transfer.
References:
[1] Lifshitz I.M., Slyozov V.V., Sov. Phys. JETP, 8 (1959) 331.
[2] Lifshitz I.M., Slyozov V.V., J. Phys. Chem. Solids, 8 (1961) 35.
[3] Wagner C., Z. Elektrochem., 65 (1961) 581.
[4] Marder M., Phys. Rev. A, 36 (1987) 858.
[5] Alexandrov D.V., J. Phys. A.: Math. Theor., 48 (2015) 035103.
S01-P04
Influence of shear rate on nucleation in oscillation baffled crystallizer
Huaiyu Yang1, Xi Yu2, Vishal Raval1, Yassir Makkawi2, Alastair Florence1,
1
2
CMAC, Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, Glasgow, UK
European Bioenergy Research Institute (EBRI), School of Engineering and Applied Science, Aston University,
Birmingham, UK
Induction times of butyl paraben - ethanol solution in batch moving fluid oscillation baffled
crystallizer with various experimental conditions e.g. amplitudes (1 - 9 mm) and frequencies (1.0 –
9.0 Hz) and induction times with 2 Hz frequency in continuous oscillation baffled crystallizer, with
or without pumping flow, have been determined. The induction time in batch moving fluid
oscillation baffled crystallizer increases with increasing amplitude and frequency below 6 Hz
frequency and below 6 mm amplitude, i.e. below about 500
power density, because of the
increase of the shear rate with increasing of frequency and amplitude. However, the induction time
increases with a further increase of the frequency and amplitude. This phenomenon, together with
the nucleation behavior of other large or small molecules under shear, may be induced by the
mechanism that decreasing size of the steady state of the clusters or density droplets before
nucleation. In the continuous oscillation baffled crystallizer with 3 mm or 5 mm amplitude, the
interfacial energy and the pre-exponential factor in both high nucleation rate region and low
nucleation rate region are determined with or without net flow by Classical Nucleation Theory. The
interfacial energy is in good agreement with literatures [1][2]. A Large Eddy Simulation approach
in Computational Fluid Dynamics framework [3] is applied to capture the shear rate conditions in
oscillatory baffled crystallizers, showing that the shear rate is of spatial periodicity with radially
symmetrisation and of temporal periodicity within sinusoidal periodic change of solution’s velocity,
and showing that net flow enhances the shear rate at most time in one circulation of the solution’s
velocity and Influence of the increasing of the amplitude and net flow, which is consistent with the
induction time experiment results in continuous oscillatory baffled crystallizer that the easier
nucleation becomes with increase of 2 mm amplitude than with increase of 60 mL/min net flow.
MFOBC FBRM or IR
COBC
Camera
FBRM or IR
Camera
Figure 2: Schema of experiment set-up of batch moving fluid oscillation baffled crystallizer (left) and continuous
oscillation baffled crystallizer (right)
Figure 1. Induction time with different frequency and amplitude in batch moving fluid oscillatory baffled crystallizer
References:
[1] H. Y. Yang and A. C. Rasmuson, Cryst. Growth Des., 2013, 13, 4226-4238.
[2] J. Liu and Å. C. Rasmuson, Cryst. Growth Des., 2013, 13, 4385-4394.
[3] X. Yu, Y. Makkawi, R. Ocone, M. Huard, C. Briens and F. Berruti, Fuel processing technology, 2014,
126, 366-382.
S01-P05
Interferometric Observation of Concentration Field during the Growth of
Tetrahydrofuran Clathrate Hydrate in the Guest/Host Boundary Layer
Kazushige Nagashima*1, Hiroaki Goto1, Hiroaki Takahashi1
1
Department of Physics, Meiji University, 1-1-1 Higashimita, Tama-ku, Kawasaki 214-8571, Japan
THF concentration
Clathrate hydrates have been paid much attention for applications such as storage and transport
of natural gas and hydrogen gas, sea water desalination and so on. Typically, gas hydrates such as
methane hydrates tend to form a film-like crystal on the surface of water between guest/host phases.
The film that separates the gas and water inhibits further growth of hydrates without being stirred to
enhance the mass transport. In our previous study [1], growth of tetrahydrofuran (THF) hydrates
were observed in THF/water concentration boundary. It was first showed that growth mode
transited from the lateral growth of hydrate film along the concentration boundary to continuous
nucleation leading to expansion of polycrystalline aggregates into both phases. In the present study,
interferometric observation of THF concentration in water was carried out to clarify the effect of
mass transport of guest molecules on the hydrate growth in the concentration boundary layer.
First of all, the pure water was injected into a vertically arranged growth cell kept at a
temperature (= 2.0~3.0°C), which is below the equilibrium temperature (= 4.4°C) of the THF
hydrate in the stoichiometric THF water solution (THF-17H2O). Then, THF (liquid) was carefully
injected on the surface of water using a micro syringe. Then, contacting the concentration boundary
layer with a chilled wire, hydrate crystals were immediately compulsorily nucleated. Without this
process, THF and water mix by diffusion. The growth process was in-situ observed using an optical
microscope and an interferometer. In addition, the initial thickness of THF/water concentration
boundary layer, L, was also observed using the interferometer. L was defined as the region of
1.1~97 wt%, as shown in Fig. 1. Note that the value of L in each run differs from each other, since
the water and THF pouring process into the cell mentioned was not completely controlled. This was
one of unknown parameters in our previous study [1].
The results showed that when the initial thickness of the concentration boundary layer L was
large, the thickness of the growing hydrate film
increased. As a result, the lateral growth rate of the
hydrate film decreased even at the same
temperature condition. The expansion rates of
polycrystalline aggregates were also affected by L,
At large L, the expansion rate of aggregates
decreased. This suggests that the mass transport
through the hydrate film was decelerated by the
thick hydrate film caused by the large L. Then, the
results of time dependent areas STHF and Sw of the
aggregates in THF and water phases showed that
the ratio of STHF to Sw was kept constant throughout
the run. The ratios obtained in all runs were around
0.15~0.37. This suggests that the same amount of
THF and water were transported per unit time
Figure 1. Interference fringes and
concentration distribution of THF in
through the hydrate film. Details will be mentioned
water in the initial condition.
in the conference.
THF
97wt%
1.1wt%
Water
References:
[1] Y. Sabase, K. Nagashima, J. Physical Chemistry B,113(2009)15304-15311.
1.3mm
2mm
S01-P06
Study of crystallization processes in Bi-doped As2S3 chalcogenide glasses using
linear isoconversion methods
Šiljegović Mirjana, Petrović Dragoslav, Štrbac Goran, Lukić-Petrović Svetlana*
Department of Physics, Faculty of Sciences, University of Novi Sad, Trg Dositeja Obradovića 4, Novi Sad (Serbia)
The kinetic analysis of the crystallization processes in Bi-doped chalcogenide glasses was
performed using the DSC method. Non-isothermal measurements were carried out at five different
heating rates and in the temperature range from room temperature to 773 K. The observed shift of
crystallization peak to higher temperatures and the increase of the enthalpy value with heating rate
is a result of a well known crystallization rate dependence upon the heat treatment speed. The
crystallization process in the sample with 3 at.% Bi was simple with the formation of only Bi2S3
crystallization centers, while in 5 at.% Bi composition the crystallization was a complex thermal
process where, in addition to the appearance of Bi2S3 type crystalline centers, the centers of
elemental As also occurred. The complexity of this process, and the fact that it takes place at the
lower temperatures compared to the crystallization of the sample with 3 at.% Bi, pointed to a lower
thermal stability of the Bi5(As2S3)95 glass and higher crystallization affinity.
The activation energy of crystallization (Ea) was determined using Kissinger Akahira-Sunose
(KAS) and Ozawa-Flynn-Wall (OFW) methods. Almost twice as high value of the parameter Ea in
the sample with the higher Bi content was interpreted by the fact that Bi addition has a growing
tendency to significantly modify the amorphous matrix structure through the chain and pyramid
structure elements formation. The Ea value for 3 at.% Bi sample does not depend on crystallization
fraction volume. In the glass with a higher Bi content reducing activation energy of the first
crystallization process was noticed in its final stage, while the second crystallization process was
characterized by the continuous increase of Ea with the crystallization fraction volume.
Figure 1. Activation energy of crystallization versus crystallized fraction according to KAS method
S01-P08
Influence of ionic surfactants on sodium chloride crystallization during evaporation
Qazi Mohsin Jahan*, Carrier Odile, Bonn Daniel, Shahidzadeh Noushine
Van der Waals-Zeeman Institute, Institute of Physics, University of Amsterdam, Science Park 904,
1098 XH Amsterdam, The Netherlands
Email: [email protected]
Sodium Chloride is one of the most abundant salts on earth and its crystallization remains very
important in different applications such as degradation and desertification of soils, physical
weathering of stones ,degradation of historical monuments , oil well productivity and CO2 storage.
On the other hand, surfactants are also widely used as cleaning agents, surface-protection agents,
clay-stabilizing agents, oil recovery agents and stone desalination agents, etc. In many of these
problems, salt and surfactants are present together in a ternary solution. These form an interesting
area of research due to their mutual influence: The concentration of salt can have a direct impact on
the surface activity of the surfactant solutions. On the other hand, the surfactants can induce
significant kinetic and morphological changes when salts crystallize 1 . In addition it has recently
been reported that certain surfactant molecules can be incorporated into the salt crystal lattice,
which generates novel composite materials with better mechanical properties 2 . However, the
mechanisms by which additives such as surfactants are entrapped in the crystal lattice and how
specific features such as their size, structure, charge and concentration affect the crystal lattice
remain still poorly understood.
The objective of this study is to investigate the crystallization dynamics of NaCl in the presence of a
charged surfactant molecule.We have studied the impact of the cationic surfactant (Cetyl
trimethylammonium bromide CTAB) on the spontaneous nucleation and growth of NaCl induced
by controlled evaporation. First, the physicochemical properties (surface tension, cmc, contact
angles) of the ternary systems CTAB-NaCl-water at different concentration of CTAB and NaCl are
characterized. Second, the kinetics of nucleation and growth of NaCl crystals was studied during
evaporation of CTAB-NaCl-Water solutions in micro-droplets and in glass microcapillaries. This
was done using phase-contrast microscopy at controlled relative humidity and temperature 3, 4.
The evaporation experiments allow to determine the volume and the concentration of the solution
throughout the drying stage. At the end of drying, the crystallization pattern at nanoscale were
studied using a High resolution Scanning Electron Microscope combined with an EDS for
elemental analysis. Our results reveal a strong interaction between the salt and the surfactant. For
the surfactants, the CMC (critical micellar concentrations) behaves non-monotonically as a function
of electrolyte concentration. For the salt, changing the concentration of the surfactant leads to
different supersaturations at the onset of crystallization, and very different crystal growth kinetics.
References:
[1].
[2].
[3].
[4].
Canselier, J. P., J. Disperison Science and Technology, 146 (1993), 625-644.
Yi-Yeoun, Kim et al, Nature Materials, 10, (2011), 890-896.
Desarnaud et al, J.Phys.chem.Lett, 5, (2014), 890-895.
N.Shahidzadeh et al, Scientific Reports,5, (2015), 10335.
S01-P09
A Study of Crystal Growth of Salicylic Acid in Organic Solvents
Jia Lijun*1, Rasmuson Ake1 2
1
Materials and Surface Science Institute, Department of Chemical and Environmental Science, University of Limerick,
Limerick (Ireland)
2
Department of Chemical Engineering and Technology, KTH Royal Institute of Technology, SE-100 44 Stockholm
(Sweden)
It is hard to overemphasize the importance of crystallization in the pharmaceutical and organic
fine chemical process industries. As two main processes of crystallization, crystal nucleation and
crystal growth together control the finial crystal product properties. Unfortunately, both kinetics and
mechanisms are poorly understood. The type or composition of solvent always influences the
crystallization behavior in both nucleation and crystal growth [1]; in our previous work, this
influence on nucleation with a simple model compound, salicylic acid, was investigated [2, 3]. In
the work here, the crystal growth rate of salicylic acid will be discussed and compared in 4 different
solvents, methanol, acetone, ethyl acetate and acetonitrile.
The isothermal desupersaturation experiments were carried out in a batch crystallizer for the
crystal growth study. FTIR probe was used for the in situ concentration measurement during crystal
growth; FBRM probe was used for validating experiment data by detection of nucleation. Figure
1(a) shows the supersaturation decay with time during crystal growth in acetone at a constant
temperature 15oC. The empirical power-law equation gives the best fit to the experiment data; from
the residual plot in figure 1(b), birth and spread model fits better than the model of BCF.
(a)
1.030
Experimental
Power law
Birth & spread
BCF
1.025
1.020
1.015
1.010
1.005
(b)
0.006
o
Acetone, 15 C
o
Acetone, 15 C
Power law
Birth & spread
BCF
0.004
Residual
Supersaturation ratio, S
1.035
0.002
0.000
-0.002
1.000
-0.004
0
500 1000 1500 2000 2500 3000 3500 4000
Time, S
0
500 1000 1500 2000 2500 3000 3500 4000
Time, S
Figure 1. (a) Measured supersaturation ratio versus time together with fitted power law (black solid line), B&S (wine
solid line) and BCF (cyan solid line) models. (b)Corresponding residuals based on the three crystal growth models.
References:
[1] R.A. Granberg and Å.C. Rasmuson, AIChE Journal, 51 (2005) 2441.
[2] D. Khamar, J. Zeglinski, D. Mealey and Å.C. Rasmuson, Journal of the American Chemical Society, 136
(2014) 11664.
[3] D. Mealey, D.M. Croker and A. Rasmuson, CrystEngComm, (2015).
S01-P10
Influence of sintering aid (SiO2) on optical properties of ceramic YAG:Cr,Ca
Vovk Oleh, Chaika Mihail*, Dulina Nadya, Doroshenko Andrey, Parkhomenko Sergei, Tolmachov Olexandr.
Institute for Single Crystals of National Academy of Sciences of Ukraine, Kharkiv, (Ukraine)
Ceramic laser materials fabricated by the vacuum sintering technique and nanocrystalline
technology [1] have gained more attention as potential solid-state laser materials in recent years. Crdoped YAG (YAG:Cr) have attracted a great deal of attention because of their potential use as
tunable solid state lasers in the spectral range 1.35-1.55 µm or passive Q-switches for laser system
based on YAG doped with rare ear ion such as Nd and Yb [2]. In ceramic technology for increasing
densification process sintering aids are used. The purpose of this work is to investigate influence of
impurity such as SiO2 and CaO on optical properties of ceramic YAG:Cr,Ca.
Two series of ceramics were sintered. First contains SiO2, second does not contain SiO2, with
different concentration of CaO. Sintering was performed by solid state reaction at 1750 OC for 10
hours in vacuum furnace. Obtained ceramics were investigated with scanning electron microscopy
(JEOL JSM-6390LV) and optical spectroscopy (Specord 200).
Ceramic YAG:Nd with SiO2, sintered in condition describe above, has grain size distribution
from 2 to 50 μm. Ceramics YAG:Cr,Ca with SiO2 and without SiO2 have a similar grain size
distribution from 0.5 to 2 μm. Therefore presence impurity CaO in ceramics YAG:Cr,Ca decreased
grain grow.
Transmission spectra of ceramics YAG:Cr with and without sintering aid SiO2 and different
concentration of CaO are presented in Fig. 1.
It was shown, that for ceramics YAG:Cr,Ca with SiO2 increasing CaO concentration increases
optical transmission. Ceramics without SiO2 demonstrate the existence of optimal CaO
concentration. Comparing transmission spectra of ceramics with and without SiO2 clearly show that
ceramics without SiO2 have better optical performance than ceramics with SiO2. The possible
reason for decreasing optical transmission in ceramics is formation of metasilicate CaSiO3
compound during vacuum sintering.
Therefore, sintering aid SiO2, which is widely used in ceramic technology, is not working in
system YAG:Cr,Ca.
Figure 1. Transmission spectra of ceramics YAG:Cr,Ca with different concentration of calcium a) with
SiO2 b) without SiO2
References:
[1] Lu J., Ueda K., Yagi H., Yanagitani T., Akiyama Y., Kaminskii A., J. Alloys Compd., 341 (2002) 220‐225. [2] Yehoshua S., Yehoshua K., Bruce H.T., J. Optical Materials, 4 (1995) 547‐551. S01-P11
Laser-Induced Nucleation in Continuous Flow
Mackenzie, Alasdair M.*; Pulham, Colin R.; Alexander, Andrew J.
The University of Edinburgh School of Chemistry, Edinburgh (UK)
*[email protected]
Continuous flow manufacturing has the ability to change the way pharmaceuticals and fine
chemicals are manufactured. Since a steady state can be achieved, a product can be manufactured
continuously within certain tolerances. For the understanding of crystallisation change in time can
be analysed by measuring different points in space. Implementation has so far faced a problem as to
how to reliably generate nucleation in a consistent manner to set t0.
Non-photochemical laser induced nucleation (NPLIN) is a technique which initiates nucleation
in a fixed irradiated volume over a nanosecond timescale. Experiments using NPLIN can often vary
from shot to shot and so many repetitions are needed to accurately describe the phenomenon.
This work develops the implementation of NPLIN into a simple continuous flow system for the
control of concentration and temperature at the point of irradiation. This enables further studies on
nucleation in a repeatable way as well as demonstrating the application of NPLIN for continuous
manufacturing.
S01-P13
Understanding of Crystallization and Growth of LiB3O5 crystal in the MoO3based high-temperature solution at the Molecular Level†
Di Wang*1, Deming Zhang2, Ji Zhang2, Shanshan Liu3, Yinchao Yue3, Guochun Zhang3, Zhanggui Hu3,
Shaotang Yin2, Peizhen Fu3, Jinglin Yu4, Mu Wang1
1
Nanjing University, National Laboratory of Solid State Microstructures and Department of Physics, Collaborative
Innovation Center of Advanced Microstructures, 22 Hankou Road, Nanjing, China
2 Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Science, 350 Shushanghu Road, Heifei, China
3 Technical Institute of Physics and Chemistry of Chinese Academy of Science, Key Lab of Functional Crystals and
Laser Technology of Chinese Academy of Sciences, 29 Zhongguancun East Road, Beijing, China
4
Shanghai University, 99 Shangda Road, Shanghai, China
In this work, we report experimental and ab initio investigations of the microstructures and
molecular dynamic of non-linear optics crystal LiB3O5 grown from the MoO3-based hightemperature solutions. Our results reveal that in the high-temperature solutions of Li2O-B2O3-MoO3
ternary system, molybdenum ions present at polyhedral sites coordinated with oxygen atoms, and
the boron-oxygen species are the various six-membered rings containing different BØ4 tetrahedrons
(Ø represents the oxygen atom shared between two cations). The molybdenum-oxide polyhedrons
and the boron-oxygen networks are not connected with each other, and prefer to be compensated
with lithium cations. Therefore, the amount of Li ions can determine microstructures of the hightemperature solutions, and then influence its crystalline habits.
Confocued Raman spectroscopy has been used to in-situ investigate the crystal-solution
interface around an as-growing LiB3O5 crystal in high temperature MoO3-based solutions. The
spectroscopic data has revealed a special growth boundary layer present in front of an as-growing
LiB3O5 crystal. In the boundary layer, boron-oxide species transform from structure units of the
bulk solution into small lattice-like growth units of the bulk crystal. On the other hand,
molybdenum ions change their coordinated numbers and are rejected away from the crystal-solution
interface. These structural investigations have suggested the solution near the crystal-solution
interface is influenced by the periodic potential of the as-growing crystal surfaces, and the packing
configuration of which is reduced with respect to the bulk solution. Based on the obtained structural
information, we propose a Li+ cation transfer reaction:
to understand growth mechanism of LiB3O5 crystal at the molecular level. Since the key role for the
crystal growth, the molecular dynamic in the boundary layer can elucide various crystal growth
phenomenon very well, such as the defect formation in bulk crystal, solute-solvent interaction and
the phase-equilibria of the Li2O-B2O3-MoO3 ternary system. Our works also indicate that the
growth boundary layer around an as-growing crystal provide a new insight into the nature of
crystallization and crystal growth mechanism in high-temperature solution.
† National Natural Science Foundation of China (Grant Nos. 51302268, 51472123)
S01-P14
Growth of doped KDP single crystals from solutions with
KMnO4 additives
Egorova Anna, Portnov Vadim
1
N.I. Lobachevsky State University of Nizhni Novgorod, 23 Gagarin Avenue BLDG 3, Nizhni Novgorod (Russia)
Crystals of potassium dihydrogen phosphate are widely applied in science and techniques,
medicine and industry.
KDP single crystals were grown using a temperature gradient technique with feeding in a
concentration convection regime [1] at a constant solution supercooling of 3.54 C°. We used zcuts of a large crystal as seeds, and solutions of two compounds: 1) analytical grade potassium
dihydrogen phosphate KH2PO4 (KDP) with a concentration of 270 g/L, analytical grade KOH
10 g/L, distilled water and the addition of 20400 mg/L of analytical grade potassium
permanganate KMnO4, pH of the solution was 4.7; and 2) KDP 310 g/L, KOH 12 g/L, distilled
water and 0200 mg/L of KMnO4, pH=5. We added alkali to prevent crystal thinning.
We have found that growth of the (101) faces of a KDP (KH2PO4) crystal is suppressed, and the
growth rate of the (100) faces passes through the maximum with increasing addition of KMnO4 to a
solution with pH=4.7. MnO2 particles deposit on the (100) faces promoting their growth. The
[MnH2PO4]2+ complexes are adsorbed on the (100) and (101) faces inhibiting the growth up to
complete stoppage. The Mn3+ ion substitutes the K+ ion in the crystal structure.
The KDP crystals with the growth sectors uniformly doped with manganese were grown in
solutions with pH=4.7 and addition of KMnO4. At higher pH, potassium permanganate undergoes
chemical transformations in a KDP solution. As a result, the concentration of manganese
compounds decreases with time in the bulk solution and, consequently, in the growing crystals. The
concentration of manganese in these crystals decreases along the growth directions.
The X-ray and electronic paramagnetic resonance data show that manganese is incorporated into the
crystal structure in the form of Mn3+ substituting a K+ ion. The optical absorption spectra of KDP
solutions with KMnO4 additives and grown crystals have been studied. The effective coefficients of
the quadratic non-linear susceptibility of crystal samples with different concentrations of
manganese have been measured. The increase of manganese concentration in the <101> growth
sectors up to 2.3·105 of the total mass fraction diminishes the effective coefficients of the quadratic
non-linear susceptibility.
References:
[1] A.V. Belyustin, N.S. Stepanova, Kristallographiya 10 (1965) 743-744.
S01-P15
Study on Growth Kinetics of Partially Deuterated Potassium Dihydrogen
Phosphate (p-DKDP) Crystals for High Power OPCPA
Guzman Luis Americo*1, Suzuki Yuta2, Urtnasan Sanduinjud3, Fujimoto Yasushi4, Fujioka Kana5
1
National Institute of Technology, Ibaraki College, 866 Nakane, Hitachinaka (Japan)
National Institute of Technology, Ibaraki College, 866 Nakane, Hitachinaka (Japan)
3
Nagaoka University of Technology, 1603-1 Kamitomioka, Nagaoka (Japan)
4
Institute of Laser Engineering, Osaka University, 2-6 Yamadaoka, Suita (Japan)
5
Institute of Laser Engineering, Osaka University, 2-6 Yamadaoka, Suita (Japan)
*email: laguzman@chem-ibaraki c-t.ac.jp
2
Discussions on the future construction of a high intense exa-watt laser, Gekko-EXA with
OPCPA amplification system has been started at ILE-Japan. Large single crystals of partial
deuterated potassium dihydrogen phosphate (p-DKDP) or K(DxH(1-x))2PO4 are suggested to generate
ultra-broad medium for OPCPA [1,2]. The optimum deuterium content in the crystal is estimated to
be 50%~80%. Therefore, for the optimal production of large crystals and to satisfy the specified
requirements (i.e size and shape) the growth rate of the crystallographic faces need to be studied. In
this study, the growth length of the {100} and {101} faces of a single KDP crystal were
investigated in partially deuterated (up to 78 mol %) saturated solutions (40℃) in a flow cell at
constant supercooling, ΔT=5℃. The crystal size increases linearly in the pure system. While, in the
deuterated solution the normalized growth length increases gradually with time as the deuteration
concentration increase reaching a maximum growth at 68 mol% D2O. Increasing more yet to a high
concentration value 78 mol% D2O, the growth decreases compared to those of low deuterium
concentrations. Thus, in some cases relatively lower growth was observed compared to the pure
system (Fig. 1). The increased and decreased growth induced by the increased deuterium content in
the solution will be explained with the isotopic effect on solubility of KDP crystals in partial
deuterated solutions and with the adsorption of some active isotope complexes on the crystal
surface causing the step advancement retardation, respectively. We also found that the growth of the
{101} face is different than the {100} face and it will be also discussed.
Normalized growth lenght ΔL/GotG [-]
2.5
2
68 mol% D2O
Crystal = KH2PO4 (KDP)
Face = {100}
T
Ts==40℃
40℃
ΔT = 5℃
57 mol% D2O
1.5
47 mol% D2O
78 mol% D2O
0 mol% D2O
1
0.5
0
0.00
10.00
20.00
30.00
40.00
50.00
60.00
70.00
time [min]
Figure 1.Face growth behavior of KDP crystals in partially deuterated solutions.
References:
[1] K. Ogawa et al., Optics Express, vol. 17 (2009) 7744-7749.
[2] T. Kurita et al., Optics Express, vol. 18 (2010) 14541-14546.
S01-P16
Thinning and thickening of free-standing smectic films
Elena S. Pikina1,2 and Boris I. Ostrovskii3,2
11
1
Oil and Gas Research Institute, Russian Academy of Sciences, Gubkin str. 3, 119333 Moscow, Russia
2
Landau Institute for Theoretical Physics of the RAS, 142432 Chernogolovka, Russia
3
Institute of Crystallography, Russian Academy of Sciences, Leninsky pr. 59, 119333 Moscow, Russia
Smectic liquid crystal is a type of self organization in which elongated molecules are arranged in stacks of liquid layers.
When stretched on a frame, these materials can form free-standing smectic films (FSSF) in which the smectic layers align parallel to
the two air-film interfaces. Here we present theoretical explanation of the thickness instabilities that occur in FSSF upon changing the
external conditions:
i) upon heating the film above the bulk smectic disordering temperature, generally the film does not rupture but instead
shows successive layer-by-layer thinning transitions;
ii) thickening of FSSF, which occurs within the thermal range of the smectic phase upon local heating.
First, we give an overview of the known experimental results. All observations reported so far can be explained on the
basis of the Landau-de Gennes theory of the smectic state in combination with nucleation theory. This is well illustrated by the
process of preparation of FSSF. Obviously, fabrication of a FSSF is an irreversible thermodynamic process, because nucleation of
dislocations is involved. This can be contrasted with ordinary liquids for which the final state of a film is governed by competition
between surface tension and gravity, and will be always the same. Then we give theoretical explanation for the thickness instabilities
in FSSF [1]. According to our findings, in overheated smectic films (thinning) or locally heated FSSF (thickening) an additional normal
tensile force appears due to a change of the mean density of the film.
In the case of an overheated FSSF the free energy has oscillatory character, and upon heating the balance of tensile and
elastic forces breaks down spontaneously, leading to mechanical instability of the film. The balance can be restored upon
spontaneous thinning of the film. Generally a regular series of such thinning transitions occurs, in which the excess layers spills over
to the film meniscus. This process necessary includes nucleation and growth of dislocation loops in the middle plane of the film. We
determined the thermodynamic conditions for a sequence of thinning transitions and derived expression for the envelope of the
actual thinning transition points. Additionally we estimated the characteristic times of dislocation loop growth. The expressions for
both the envelope of thinning points and the dynamics of dislocation loops growth are in good agreement with experiments.
Local heating of a FSSF within the smectic temperature range induces thermal expansion, which shifts the system to a
metastable state. We showed that at relatively large heating (but not too large, to avoid any transition to the nematic or isotropic
state) nucleation and growth of dislocation loops of excess smectic layers in the middle plain of the film becomes energetically
favorable. At a certain stage of heating, the activation energy for the formation of such dislocation loops becomes smaller than the
threshold energy and decreases upon further heating. This leads to local film thickening by many tens of layers. The realization of
this scenario crucially depends on the energy dissipated locally in the film. Estimates of the thickness of the growing “island” in the
film and of the velocity of the dislocation loop growth are in reasonable agreement with experiments [2].
1. E. S. Pikina, B. I. Ostrovskii and W. H. de Jeu, Eur. Phys. J. E 38: 13 (2015).
2. W.H. de Jeu, A. Fera, B.I. Ostrovskii, Eur. Phys. J. E 15, 61 (2004).
S01-P17
In-situ SAXS studies of crystal structures of C16/C18 binary system during crystallisation
and phase transformations in melts
Xue Tang*1, Xiaojun Lai1, Kevin J. Roberts1
Ken Lewtas2 and Iain More2
1
Institute of Particle Science and Engineering, School of Chemical and process Engineering,
University of Leeds, Leeds LS2 9JT, United Kingdom
2
Infineum UK Ltd, Milton Hill Business and Technology Centre, Abingdon,
OX13 6BB, UK
Understanding the crystallisation of C16H24 and C18H38 alkane solution is very important to ensure
trouble-free operation in diesel fuels [1]. However, for the binary mixtures of C16H24 and C18H38, the
crystallisation transition behaviour and resultant structures, as a function of their compositions has
not been clearly defined [2]. These structural changes are best examined by in-situ SAXS studies
using synchrotron radiation to characterise the early molecular scale aggregation stage prior to the
crystallisation and to probe a fundamental perspective for their self-assembly into clusters and
nuclei and the subsequently into 3D ordered crystal structure.
MSZW has been determined by DSC measurements performed on 11 binary mixed samples of
C16H24 and C18H38 varied 10% of molecular weight of C18H38. This work also characterised the
phenomenon of these binary mixtures crystallising via some rotation phases from high temperature
region and then transferred into some stabilized crystallographic phases around the low
temperature region.
SAXS studies at the beamline X27C in NSLS using a poly-thermal cooling crystallisation process
at 0.1 °C/min from 35 °C to 10 °C were also carried out. Examination of the data shows an
increase in the slope of scattering intensity as a function of the q range from 0.007-0.2 Å-1
consistent with a change in molecular ordering prior to crystallisation, followed by a much more
abrupt change at the crystallisation onset. This gives the evidence of the possibility to apply the insitu SAXS technique associated with the examination of crystallisation process.
[1] D.L Klass., Biomass for renewable energy, fuels, and chemicals. 1998:
[2] E B. Sirota, et al., The Journal of Chemical Physics, 1993, 98(7), pp.5809-5824.
S01-P18
Solution state studies of C16H24/C18H38 binary system in dodecane from poly-thermal
crystallisation process
Xue Tang*1, Xiaojun Lai1, Kevin J. Roberts1 and Diana M. Camacho Corzo1
Ken Lewtas2 and Iain More2
1
University of Leeds, Leeds LS2 9JT, United Kingdom
2
Infineum UK Ltd, Milton Hill Business and Technology Centre, Abingdon,OX13 6BB, UK
Studies of solution behaviour of binary mixtures of normal alkanes C16H24/C18H38, the dominant
component of biofuels derived from hydrogenated vegetable oils (HVO)1 have been examined by a
poly-thermal cooling crystallisation process. Saturation temperatures and MSZW have been
measured for the n-alkanes C16H24 and C18H38 and for their 9 binary mixtures in different molar
ratios from n-dodecane solvent.
Saturation temperatures are found to reflect the higher lattice stability as showed in Fig 1 below.
The decrease in saturation temperature observed over the temperature rangefor 0.1 to 0.4 C18H38
in C16H24 mixtures is due to the formation of some phases with higher solubility and hence lower
lattice stability than that of the triclinic phases of single C16H24 or C18H38.
Equilibrium solubility of each composition is also used to perform Van ’t Hoff plot with calculated
ideal solution activity. The corresponding activity coefficients for all mixtures for 11 binary mixtures
in n-dodecane solvent dhowed negative deviation to ideal solutions, with the pure solutes of C16H24
and C18H38 generally more close to the ideal condition with smaller values of activity coefficient (γ).
The equimolar mixture (0.5C16H24/0.5C18H38) shows the largest values from 1.95-2.55 indicates the
largest deviation from the ideal activity.
[1] R. G. Mason and H. L. Rice, 1979. Hydrogenated vegetable oil. Google Patents.
S01-P19
Nucleation of amine soaps
Booth, David R.*1, Lai, Xiaojun1, Robles, Eric2
1
Institute of Particle Science and Engineering, University of Leeds, LS2 9JT, UK
2
Procter & Gamble Newcastle Innovation Centre, Newcastle, NE12 9TS, UK
Amine soaps are used as surfactants in a broad range of products. The most commonly
encountered amine soaps are alkanolammonium carboxylates. Despite their widespread use, there is
little information available in literature regarding their phase behavior especially compared to their
sodium soap equivalents [1, 2]. The information that is available focuses on their behavior above
the Krafft boundary and doesn’t give any insight into their precipitation or crystallisation below the
Krafft boundary.
This present study has determined the metastable zone width for four different
alkanolammonium carboxylate-water systems, focusing on the micellar region of the phase diagram
(<20% wt soap). Monoethanolamine was used to produce soaps of the following saturated fatty
acids; lauric (C12:0), myristic (C14:0), palmitic (C16:0), stearic (C18:0). The metastable zone
width was determined using polarized optical microscopy, turbidity measurements, and DSC. The
precipitate was studied using simultaneous SAXS and WAXS to distinguish crystals from liquid
crystals.
The nucleation kinetics of the soaps were compared using Nyvlt’s approach as the observed
kinetics were a combination of the crystallization kinetics and the kinetics of the dissolution of
micelles. The obtained nucleation orders were compared with those already available in literature
for the equivalent sodium soaps [3]. The monoethanolammonium soaps showed the same trend as
their sodium equivalents of decreasing nucleation orders with chain length.
References:
[1] Zhu, S. et al. J Phys Chem B. 109(2005),11753.
[2] Warnheim, T. and Jonsson, A. J Colloid Interface Sci. 138(1990), 314.
[3] van Gelder, R.N.M.R. et al. J Cryst Growth. 166(1996), 189.
S01-P20
Nucleation, crystal growth kinetics and morphology of methyl stearate as a function of
solution environment
Camacho Corzo Diana Milena*1, Roberts Kevin J1, Thomas Danielle1, Lewtas Ken2, More Iain2
1Institute
of Particle Science and Engineering and Institute of Process Research and Development, School of Chemical and Process
Engineering, University of Leeds, Leeds, LS2 9JT, UK
2Infineum UK Ltd, Milton Hill Business and Technology Centre, Abingdom, OX13 6BB, UK
The nucleation, crystal growth kinetics and morphology of methyl stearate crystallising from three different
solvents: n-dodecane, kerosene and toluene is analysed. A polythermal methodology is used in connection
with the recently proposed KBHR (Kashchiev, Borissova, Hammond, Roberts) model [1, 2], to assess the
mechanisms and the kinetics of nucleation of methyl stearate crystallising from solutions with concentrations
ranging from 200 to 350 g/l. The analysis reveals in all cases a progressive nucleation mechanism and
values between 0.94-1.55, 1.21 - 1.91 and 1.16-2.27
for methyl
crystallite interfacial tension
stearate crystallising from n-dodecane, kerosene and toluene respectively. Nucleation rates calculated using
the obtained values of
and the number of crystals at the detection point
range between 2.6 x 1014
and 4.9 x 1015
, with the highest rates predicted for methyl stearate crystallising from n-dodecane
solutions.
A detailed analysis of the crystal morphology for methyl stearate, using a methodology based on a
combined BFDH and zone axis analysis [3] yields the morphological indexation to be <111> based on the
expected orthorhombic crystal structure. Crystals growing from supersaturated n-dodecane, kerosene and
toluene solutions, as study using in-situ optical microscope, at supersaturation (σ) levels of 0.3-0.42, 0.45-0.52
and 0.04-0.08 respectively, reveal that the crystal morphology changes only in the case of methyl stearate
crystallising from kerosene at the lowest supersaturation values. The growth rates measured in toluene for the
(1-11) face are of the same order of magnitude to those observed in kerosene, ranging from 0.02 to 0.37
and are around half those observed in n-dodecane solutions, in which these values range from 0.09 to
0.82
. Measurements of the growth for the (111) face in the case of kerosene solutions, are much lower
, which gives these
in magnitude compared to those for the (1-11) face, ranging from 0.01 to 0.15
crystals an elongated lozenge shape. On the other hand, similar growth rates values are observed between
the (111) face and the (1-11) face for crystals growing from n-dodecane and toluene solvents, ranging from
0.11 to 1.05 and 0.04 to 0.35 respectively. The tendency of the growth rates dependence on σ is consistent
with a Birth and spread (B&S) growth mechanism for growth from n-dodecane and with a BCF mechanism for
growth from kerosene and toluene solvents.
References:
[1] D. Kashchiev, A. Borissova, R.B. Hammond, K.J. Roberts, Dependence of the Critical Undercooling for
Crystallization on the Cooling Rate, J Phys Chem B, 114 (2010) 5441-5446.
[2] D. Camacho, A. Borissova, R. Hammond, D. Kashchiev, K. Roberts, K. Lewtas, I. More, Nucleation
mechanism and kinetics from the analysis of polythermal crystallisation data: methyl stearate from kerosene
solutions, Crystengcomm, 16 (2014) 974-991.
[3] D. Camacho, K.J. Roberts, K. Lewtas, I. More, Nucleation, Crystal Growth Kinetics and Morphology of
Methyl Stearate as a Function of Solution Environment, Journal of Crystal Growth, 10.1016/
j.jcrysgro.2015.01.006.
S01-P21
Metastability limit for the nucleation of NaCl crystals in confinement
Julie Desarnaud1, Hannelore Derluyn2.3, Jan Carmeliet3, Daniel Bonn1, Noushine Shahidzadeh1
1
University of Amsterdam, Institute of Physics, Science Park 904, 1098 XH Amsterdam (The Netherlands)
University of Ghent, Department of Geology and Soil Science – UGCT Krijgslaan 281 S8, 9000 Gent, (Belgium)
3
ETH, Institut für Technologie in der Architektur, HIL E 46.3, Wolfgang-Pauli-Str. 15, 8093 Zürich (Switzerland)
2
Crystallization in porous media is very important in many applications such as oil recovery, civil
engineering, soil mechanics and protein purification: for civil engineering and geology, salt
crystallization, is one of the major causes of mechanical or physical weathering causing
disintegration of rocks and building materials [1-2] . Moreover, salinisation and sodification are a
serious form of soil degradation causing desertification of soils in Europe. For proteins, it was also
shown recently that the nucleation of protein crystals on mesoporous materials can be a very
promising avenue for protein crystallization [3,4]. For most if not all of the above-mentioned
applications, the precise conditions under which NaCl crystals nucleate and growth from solution
are very important but largely unknown..
We have investigated the spontaneous nucleation and growth of NaCl crystal induced by controlled
evaporation in confined geometries (microcapillary) spanning several order of magnitude in
volume[7]. Our results show that supersaturation achieved at the onset of spontaneous primary
nucleation and growth is around 1.6 and remains independent of the size, shape, and surface
properties of the microcapillary. We show from classical nucleation theory that this is expected: S~
1.6 corresponds to the point where nucleation first becomes observable on experimental timescales.
A consequence of the high supersaturations reached at the onset of nucleation is the very rapid
growth of a single skeletal (Hopper) crystal [5]. Experiments on porous media (sandstone) also
reveal the formation of Hopper crystals in the entrapped liquid pockets in the porous network and
consequently underline the fact that sodium chloride can easily reach high supersaturations, in spite
of what is commonly assumed for this salt.
Spontaneous growth of Hopper crystals at supersaturation S∼ 1.6, in a square microcapillary (50 m)5.
References:
[1]. . Shahidzadeh-Bonn N, Desarnaud J., Bertrand F., Chateau X., Bonn D., Phys. Rev. E. 81,
(2010), 066110.
[2]. N.Shahidzadeh and J.Desarnaud, Eur. Phys. J. Appl. Phys. 60, (2012), 24205.
[3]. A.J.Page and R.P.Sear, JACS, 131, (2009), 17550.
[4]. Diao Y., Harada T., Myerson A.S, Hatton T., Trout B.L., Nature materials, 10 (2011), 867871.
[5]. Desarnaud J., Derluyn H. , Carmeliet J., Bonn D., Shahidzadeh N., J. Phys. Chem. Let. 5, (2014)
890-895.
S01-P22
The role of alanine, aspartic acid and lysine as simple models of organic matrix
molecules participating in calcium carbonate biomineralization
L. Štajner, D. Kralj
Ruđer Bošković Institute, Bijenička cesta 54, 10000 Zagreb, Croatia
Calcium carbonates could be biomineralized by different invertebrate organisms, either in a
form of certain polymorph (calcite, vaterite and aragonite) or hydrated modification. The formation
of specific crystal modification or appearance of appropriate morphological form can be influenced
by parameters like temperature, pH or supersaturation, as well as by the presence of inorganic
components or biomolecules. At that, the important organic components of extrapallial fluids, in
which the biomineralization takes place, are proteins. Previously, the influence of isolated
fragments
of proteins extracted from mineralized tissues, or their synthetic macromolecular
analogues has been investigate in the appropriate calcium carbonate model systems.1, 2 ,3
The aim of this research is to investigate the influence of amino acids, selected as simple
models of biomacromolecules supposed to be responsible for nucleation, growth and transformation
of calcium carbonates in biomineralizating systems. For that purposes, alanine (Ala), lysine (Lys)
and aspartic acid (Asp) were used. Besides their chemical differences, at the conditions applied in
the selected model systems the used amino acids have different net charges as well: Ala is neutral,
Lys is positive and Asp is negatively charged. The results of potentiometric, spectroscopic,
chemical, structural (PXRD) and microscopical (SEM) analyses indicated the overall inhibition of
calcite precipitation in the presence of Lys and Aps, that (inhibition) is probably caused by slower
transformation of initially formed vaterite, into calcite.4 Since both amino acids are charged at
applied experimental conditions, some non specific surface interactions are assumed to be
responsible for observed effect. The additional kinetic experiments and molecular modelling will be
necessary to reveal the nature of respective intermolecular interactions.
[1] A. Adamiano et al, (2012) Chem. Eur. J 18 14367 – 14374.
[2] B. Njegić-Džakula et al., (2013) Croat. Chem. Acta 86 39–47.
[3] .B. Njegić Džakula et al., (2009) Cryst. Growth Des. 9 2425-2434.
[4] D. Kralj et al., (1997) J. Cryst. Growth 177 248-257.
S01-P23
Crystallization kinetics of iron inclusion in magnesium aluminosilicate glass
processed by laser floating zone technique
Nuno M. Ferreira1*, Andrei V. Kovalevsky2, Manuel A. Valente1, Nikolai A. Sobolev1, João C. Waerenborgh3,
Jorge R. Frade2, Florinda M. Costa1
1
Department of Physics, i3N, University of Aveiro, Portugal
CICECO – Aveiro Institute of Materials, Department of Materials and Ceramic Engineering, University of Aveiro,
3810-193 Aveiro, Portugal
3
Centro de Ciências e Tecnologias Nucleares, Instituto Superior Técnico, Universidade de Lisboa, 2695-066 Bobadela
Lisboa, Portugal
2
Magnesium aluminosilicate (MAS) glasses were proposed as a base molten electrolyte for iron
pyroelectrolysis, an alternative electrometallurgical technique which offers prospects for
environmental and economic advantages over traditional steelmaking [1,2]. This work is focused on
the assessment of mechanisms for iron incorporation in the MAS glass system and related effects on
their physical properties [3-5]. Faster pulling rates were found favorable for the formation of
isolated iron cations in the glass forming network. The crystallization process (slower pulling rates),
accompanied with separation of mullite and cordierite-type phases, is strongly affected by the
formation of nanosized iron-containing clusters, confirmed by Mössbauer and EPR spectroscopies.
LFZ method shows good prospects for studying the crystallization mechanisms in silicate-based
glasses with additions of redox-active cations, by providing flexibility in tuning their oxidation state
and attaining frozen-in conditions.
References:
[1] – N.M. Ferreira, A.V. Kovalevsky, S.M. Mikhalev, F.M. Costa, J.R. Frade, Prospects and challenges of
iron pyroelectrolysis in magnesium aluminosilicate melts near minimum liquidus temperature, Phys. Chem.
Chem. Phys., 17 (2015) 9313-9325. Doi: 10.1039/c5cp00858a
[2] – N.M. Ferreira, A.V. Kovalevsky, J.C. Waerenborgh, M. Quevedo-Reyes, A.A. Timopheev, F.M. Costa
and J.R. Frade, Crystallization of iron-containing Si-Al-Mg-O glasses under laser floating zone conditions, J.
Alloys Comp. 611 (2014) 57–64.
[3] – I. Fanderlick, Silica glass and its application, Elsevier Science Publishers: Amsterdam, 1991.
[4] – B. Mysen, P. Richet, Silicate glasses and melts: properties and structure, Elsevier: Amsterdam, 2005.
[5] – A. Mekki, Magnetic Properties of Fe ions in a silicate glass and ceramic, Phys. Status Solidi A 184 (2001)
327–333.
S01-P24
The NMR study of He enclosed in nanotubes MCM-41
3
Mikhin Nikolay, Birchenko Oleksandr, Fysun Yana*1
1
B.Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine,
47 Lenin Ave., Kharkov 61103 (Ukraine)
MCM-41 is a mesoporous molecular sieve of SiO2. It consists of a uniform array of parallel
quasi-1D straight honeycomb mesopores. It is a powder sample where the pore length is equal to
the grain size of
300 nm. MCM-41 can be produced with a variety of different pore sizes. In our
case a pore diameter is about 2.5 nm.
At low temperatures (T <10 K) the powder MCM-41 is effective adsorbent of noble gases (in
our case – helium-3) with good absorbency (specific surface area ~ 1000 m2/g). Moreover, 99% of
the adsorbing surface is the inner surface of the tubes [1]. It has known that roughly first 1.8
monolayers of adsorbed helium have the structure of disordered solid [2]. Next additional portions
of 3He have the properties of a “rarefied" liquid. This quasi-one-dimensional object is supposed to
have properties of Tomonaga-Luttinger liquid, low-dimensional structure of the 3He fermions [3]
3
He adsorbed in 0.4 cm3 of MCM-41 powder was investigated by pulse NMR method
(ω0/2π=9.15 MHz). Spin-lattice T1 and spin-spin T2 relaxation times, as well as D spin-diffusion
coefficient were measured in the temperature range 1.3-2 K. It was found at least two different
contributions to the NMR signal, which can be associated with “disordered solid” and “rarefied
liquid” phases of 3He mentioned above. The results obtained in the experiments are discussed
References:
[1] C. Kresge, M.E. Leonowicz, W.J. Roth, J.C. Vartuli, J.S. Beck, Nature 359, (1992) 710
[2] N. Wada,·T. Matsushita,·M. Hieda,·R. Toda, J. Low Temp Phys 157, (2009) 324
[3] B. Yager, J. Nye´ki, A. Casey, B. P. Cowan, C. P. Lusher, J. Saunders, PRL 111, (2013) 215303
S01-P25
Block copolymer aggregates on planar substrates:
Impact of preparation conditions and surface wettability
José Danglad Flores*, Hans Riegler
Max-Planck-Institute of Colloids and Interfaces, Am Mühlenberg 1 OT Golm 14476, Germany
Block-Copolymer solutions (PS-PMMA-toluene) are spin cast onto planar surfaces. Meanwhile the
spin casting process; the film thinning due to the hydrodynamic-evaporation has been understood
quantitatively [1]. The thinning film may eventually dewet into droplets. This dewetting depends on
a) the spin casting conditions (speed, temperature, evaporation rate, etc.); b) the initial PS-PMMA
concentration, and c) the substrate surface wetting properties.
We investigate (by AFM) how a) the preparation process (spin casting parameters), b) the global
surface wetting properties, and c) the local surface wetting properties (nano-patterned surfaces)
affect the resulting PS-PMMA aggregate morphology. Thus we want to eventually control and
manipulate the resulting self-assembly block copolymer patterning.
Graphical Abstract. Different morphologies of block-copolymer aggregates on different substrate surfaces: a) on an
Alkychlorosiloxane-coated surface [2], b) on a baked thin film of block-copolymer[3], c) on silica[4].
Reference
1.
2.
3.
4.
Karpitschka, S., C.M. Weber, and H. Riegler, Spin casting of dilute solutions: Vertical composition profile
during hydrodynamic-evaporative film thinning. Chemical Engineering Science, 2015. 129(0): p. 243-248.
Peters, R.D., et al., Wetting Behavior of Block Copolymers on Self-Assembled Films of Alkylchlorosiloxanes:
Effect of Grafting Density. Langmuir, 2000. 16(24): p. 9620-9626.
Bang, J., et al., Facile Routes to Patterned Surface Neutralization Layers for Block Copolymer Lithography.
Advanced Materials, 2007. 19(24): p. 4552-4557.
Buck, E. and J. Fuhrmann, Surface-Induced Microphase Separation in Spin-Cast Ultrathin Diblock Copolymer
Films on Silicon Substrate before and after Annealing. Macromolecules, 2001. 34(7): p. 2172-2178.
S01-P26
Switching off Non photochemical laser induced nucleation by use of nanofiltration
Thomas Kendall*1,2, Dr Nadeem Javid1, Dr Iain Burns1, Prof Jan Sefcik12.
University of Strathclyde1, James Weir Building 75 Montrose Street, Glasgow (UK)
CMAC2, Technology and Innovation Centre Level 6, 99 George Street, Glasgow (UK)
[email protected]
We have investigated the effect of nanofiltration on non-photochemical laser induced nucleation
(NPLIN) in order to provide better understanding of underlying nucleation phenomena. We used linearly
polarized nanosecond pulsed laser light of wavelength 1064 nm to irradiate glycine solutions at various
supersaturations (1.4-1.6) under isothermal conditions. The nucleation behaviour showed strong
supersaturation dependence in terms of probability distribution of nucleation induction times, where the
nucleation probability increased systematically with increasing supersaturation as expected. Surprisingly, a
bimodal distribution of nucleation induction time was observed in unfiltered solutions, with a first relatively fast
regime followed by a second slow regime for all supersaturations studied. The nanofiltration of the
undersaturatred solutions before their cooling to the desired crystallisation temperature resulted in drastically
reduced nucleation probability and only the second slow regime of nucleation distribution was observed across
all the supersaturations. This suggests that the filtration removed nanoscale nucleation prone moieties from
solutions which interact with laser to induce nucleation. When solutions were investigated with dynamic light
scattering we found there was a reduction in both the size and intensity of solute mesoscale clusters which
suggests a possible link between these solute clusters and NPLIN.
We also investigated the effect of irradiation on polymorphism for unfiltered solutions at different
supersaturations: the lower supersaturation (1.4) predominantly yielded α polymorph and higher
supersaturations (1.5 and 1.6) showed enhanced γ polymorph nucleation (41 % crystals were γ form). The
filtered solutions (both irradiated or non-irradiated) nucleated predominantly as α polymorph. We therefore
hypothesize that the glycine mesoscale clusters play a major role in laser induced nucleation and polymorph
control in aqueous glycine solutions.
Figure 1. Cumulative distribution of induction times for laser induced nucleation in filtered & non-filtered and
irradiated & non-irradiated glycine aqueous solutions (supersaturation 1.6)
SESSION 2
Theory and Modeling
Collaboration of atomic and macro scale calculations: polytype and defect
control of wide ba111ndgap materials
Koichi Kakimoto*1, Bing Gao1, Shin-ichi Nishizawa2, Satoshi Nakano1, Yoshihiro Kangawa1
1
RIAM, Kyushu University, 6-1, Kasuga-koen, Kasuga, Fukuoka, (JAPAN)
2
AIST, 1, Umezono, Tsukuba, Ibaraki, (JAPAN)
Modeling of crystal growth by numerical method plays an important role to predict phenomena
in macro- and microscopic point of views. This paper focuses on the process of crystal growth of
SiC by physical vapor transport. Crystal growth of a certain polytype of SiC in a process of physical
vapor transport was studied on the basis of classical thermodynamic nucleation theory in
conjunction with numerical results obtained from a macroscopic global model. Formation of a
certain polytype in the nucleation stage is determined by the energy balance among surface energy
which is obtained by the first principle calculation in an atomic scale, formation energy and
supersaturation. The preferential growth condition of a certain polytype was estimated. The value of
super saturation was estimated using a numerical model obtained by a global model that includes
species transport as well as heat transport in a furnace. The results of calculation showed that 4Hpolytype is mores table than 15R, 6H and 3C-polytypes. Free energy difference between 4H- and
6H-polytypes decreased when total pressure in the furnace decreased [1-3].
The effect of nitrogen and aluminum as doped impurities on the stability of SiC polytypes (Cor Si-face 4H and 6H substrates) formed by physical vapor transport (PVT) was investigated. The
results reveal that the formation of 4H-SiC was more stable than that of 6H-SiC when a grown
crystal was doped with nitrogen using C-face 4H- and 6H-SiC as seed crystals. In contrast,
formation of 6H-SiC was favored over 4H-SiC when Si-face 4H- and 6H-SiC seed crystals were
used. Meanwhile, the formation of 4H-SiC was more stable than that of 6H-SiC when aluminum
was the dopant and C- and Si-faces of 6H-SiC were used as seed crystals. Formation of 6H-SiC
occurred over that of 4H-SiC in the cases of C- and Si-faces of 4H-SiC as seed crystals.
To dynamically model the plastic deformation of 4H–SiC single crystals during physical vapor
transport (PVT) growth, the Alexander–Haasen model, originally proposed for the elemental
semiconductor, is extended into IV–IV compound semiconductors. By fitting the model parameters
to the experimental data, we show that the Alexander–Haasen model can describe the plastic
deformation of 4H–SiC single crystals if the activation of the carbon-core partial dislocation is
modeled in the high-temperature region (above1273 K) and the silicon-core partial dislocation is
modeled in the low-temperature region (below 1273 K). We then apply the same model to the
dynamical deformation process of a 4H–SiC single crystal during PVT growth. The time evolution
of the dislocation density is shown, and the effects of the cooling time on the final dislocation
density, residual stress and stacking faults are also examined [4-7].
References:
[1] K. Kakimoto, et al., J. of Crystal Growth, 324 (2011) 78.
[2] T. Shiramomo, et al., J. of Crystal Growth, 352, (2012) 177.
[3] T. Shiramomo, et al., J. of Crystal Growth, 385, (2014) 95.
[4] Bing Gao and Koichi Kakimoto, Cryst. Growth Des., 14 (2014) , 1272.
[5] Bing Gao, et al., J. of Crystal Growth, 386, (2014) 215.
[6] Bing Gao, et al., J. of Crystal Growth, 392, (2014) 92.
[7] Bing Gao, et al., J. of Crystal Growth, 396, (2014)7.
Gaining understanding of crystal growth processes via modeling: Pushing the
continuum from the top down
Yutao Tao, Andrew Yeckel, and Jeffrey J. Derby*
Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN 55455, U.S.A.
From a modeling and simulation perspective, crystal growth processes represent some of the
most complex and challenging systems ever analyzed, requiring a multidisciplinary and multi-scale
approach and drawing on a wide range of scientific and engineering expertise. This lecture will
describe continuum transport processes at play during crystal growth from a mathematical and
computational modeling perspective.
Recent results from research studies will be used to illustrate these modeling concepts. In
particular, we will discuss models for the interactions of solid particles with a moving solidliquid interface, focusing on silicon carbide (SiC) particles in multi-crystalline silicon. We present
a continuum model that allows for a rigorous representation of forces across disparate length scales,
including van der Waals interactions arising from atomistic effects. We demonstrate how this model
is able to represent large deformations of the melt-solid interface during the process of engulfing a
solid particle that is on the order of 1-10 microns in size. Of particular interest is the inclusion of a
physically motivated, pre-melted liquid layer in the problem formulation. Our finite-element
representation permits nanometer-scale resolution of this layer, which, importantly, circumvents the
use of arbitrary cut-off values for determining minimum gap thickness prior to particle engulfment.
We present validation of our approach by comparison to select analytical results and to ongoing
experiments of the ParSiWal project, funded by the German DLR and involving the Fraunhofer
IISB, University of Freiburg, and University of Bayreuth. We address the critical factors that
determine the transition from the stable pushing of a particle by a solid-melt interface to conditions
where engulfment is inevitable. Of particular interest and relevance is the discovery that oscillating
solidification fronts, as would arise due to turbulent fluctuations in large-scale silicon melts, can
drive engulfment of silicon carbide particles at average growth rates far below those predicted by
prior steady-state analyses.
Figure 1. Computation of a SiC particle engulfed by solidifying silicon. (a) Snapshot of finite element
mesh used in this calculation, with particle and solidification front indicated in red. (b) System
geometry, with solute concentration field (left) and temperature contours (right). Our model
accurately resolves a thin, premelted liquid layer, on the order of nanometers in thickness.
_________________
This research was supported in part by U.S. National Aeronautics and Space Administration,
NNX10AR70G; no official endorsement should be inferred.
Study on the usage of a commercial software (Comsol multiphysics®) for
dislocation multiplication model
B. Gallien, M. Albaric , J.P. Garandet, T. Duffar, K. Kakimoto , M. M’Hamdi
Keywords: dislocation density, plasticity, numerical simulation, photovoltaic silicon,
Elaboration of silicon ingots for photovoltaic application in Directional Solidification furnace leads
to formation of defects in crystal lattice. Among these defects which impact photovoltaic
conversion rate, there are dislocations, linear defects due to stresses. Several teams around the
world have created numerical simulation using home-made software in order to study dislocation
multiplication and predict the dislocation density inside ingots during elaboration.
In this study, the commercial software Comsol multiphysics®, is used to calculate the evolution of
dislocation density during the ingot solidification and cooling. Thermo-elastic stress, due to
temperature field inside the ingot during elaboration, is linked to the evolution of the dislocation
density by the Alexander and Haasen model (A&H model). The purpose of this study is to show
relevance of commercial software to predict dislocation density in ingots.
In a first, A&H physical model is introduced for a 2D axisymmetric geometry. After a short
introduction, modification of Comsol software is presented in order to include A&H equations. This
numerical model calculates dislocation density and plastic stress continuously during solidification
and cooling of ingot. Results of this model are then compared to dedicated home-made simulation
software. Results are also compared to characterization of a silicon ingot elaborated in a gradient
freeze furnace. Both of this comparison shows the relevance of using a commercial code, as
Comsol, to predict dislocations multiplication in a silicon ingot during elaboration.
Atomic scale design of epitaxial interfaces: clusters, stripes and nanowires
Michail Michailov and Bogdan Ranguelov
Institute of Physical Chemistry, Bulgarian Academy of Sciences, Sofia 1113 Bulgaria
email: [email protected]
The present lecture outlines an important area in the application of computer modelling to
crystal growth, surface and interface phenomena. Being relevant to the fundamental physical
problem of competing atomic interactions in systems with reduced dimensionality, these
phenomena attract special academic attention. On the other hand, detailed knowledge of the fine
atomic structure of interfaces is essential for understanding and solving a large number of practical
problems in contemporary material science. Typical examples are formation of nanoscale surface
patterns, two-dimensional superlattices, atomic intermixing at epitaxial interface, transport
phenomena of atoms and atomic clusters, structure and stability of quantum wires on surfaces. In
the present report we discuss a variety of diffusion mechanisms that control nanoscale interface
patterning by surface-confined atomic exchange, formation of alloyed atomic stripes and islands,
relaxation of pure and alloyed atomic terraces, migration of clusters and their stability in external
field. The computational Monte Carlo model refines important details of diffusion of adatoms and
clusters accounting for the energy barriers at specific atomic sites: smooth domains, terraces, steps
and kinks. This systematization imply classification order of surface alloying: blocked, incomplete,
and complete. The diffusion kinetics, integrity and decomposition of atomic islands in an external
field are considered in detail and assigned to specific energy regions depending on the cluster
stability in mass transport processes. Step roughening impact on atomic step permeability
phenomena is discussed. The presented ensemble of diffusion scenarios opens a way for nanoscale
surface design towards regular atomic interface patterns with exotic physical features. Finally, the
lecture discusses the problem of thermal stability of metal nanowires on crystal surfaces. The
spontaneous breakdown of free-standing or interface-located monatomic nanowires is considered in
a model involving consecutive three-step mechanism for nanowire rupture, grounded on formation
of active atoms, atomic vacancies and vacancy clusters. The present report also demonstrates the
extended capability of atomistic models in computer simulations to unravel simultaneously acting
effects, to distinguish between them, and finally to evaluate their specific contribution to
experimentally observed complex physical phenomena.
References:
[1] M. Michailov “Classification Order of Surface-Confined Intermixing at Epitaxial Interface” in: “Nanophenomena at
Surfaces: Fundamentals of Exotic Condensed Matter Properties”, Springer Series in Surface Science 47, Chapter 6, p.
145-168, M. Michailov (Ed), Springer, Berlin Heidelberg 2011
[2] M. Michailov “Computational Study of Stripe Alloy Formation on Stepped Surfaces” Phys. Rev. B, 80, p. 035425
(2009)
[3] M. Michailov, M. Vladkov “Surface Diffusion of Pb Clusters on Cu(111) Influenced by Size Dependent ClusterSubstrate Misfit: Monte Carlo Tight Binding Simulation Model” Surface Science 601, 18, p.3912 (2007)
[4] B. Ranguelov and M. Michailov “Atomic diffusion on vicinal surfaces: step roughening impact on step
permeability” Journal of Phys. CS 558 (2014) 012004
[5] M. Michailov, D. Kashchiev “Monatomic metal nanowires: “Rupture kinetics and mean lifetime”, Physica E 70
(2015) p.21–27
Numerical analysis of dislocation density in multicrystalline silicon for solar cells
using experimental verification
Satoshi Nakano1, Bing Gao1, Karolin Jiptner2, Hirofumi Harada2, Yoshiji Miyamura2, Takashi Sekiguchi2,
Masayuki Fukuzawa3and Koichi Kakimoto1
1
Research Institute for Applied Mechanics, Kyushu Univ., 6-1 Kasuga-koen, Kasuga, Fukuoka 816-8580 (Japan)
2
NIMS, 1-1 Namiki, Tsukuba, Ibaraki, 305-0044 (Japan)
3
Kyoto Institute of Technology, Matsugasaki, Kyoto, 606-8585 (Japan)
In recent days, monocrystalline silicon is mainly produced by the Czochralski method. This
method can produce high-quality and dislocation-free silicon ingot, but production cost is high. The
directional solidification technique can produce multicrystalline silicon ingot for solar cells and
reduce the production cost. However dislocations in multicrystalline silicon have been identified as
one of the most problem for improving the efficiency of solar cells [1]. Therefore, it is necessary for
the demand of increasing the efficiency of solar
cells to reduce the dislocation density. Experimental
measurement is an important method for evaluating
the quality of silicon for solar cells [2], but it is very
difficult to clarify how to multiply dislocation
density during growth and cooling process.
Moreover, it is also difficult to investigate how to
reduce the dislocation density. Therefore, numerical
simulation is an important tool for having these
knowledge.
We
developed
the
three-dimensional
Alexander–Haasen model to investigate distribution
of dislocation density in the crystal [3, 4]. Figure 1
shows the ditribution of disloaction density at
center line as a function of the height from the
bottom of the crystal. The results show that the Figure 1. Disloaction density at center line
dislocation density in the crystal for calculation as a function of the height from the bottom
data is close to that for experimental data. of the crystal
Therefore, we can predict the dislocation density
more quantitavely by using our method.
Acknowledgement
This work was partly supported by the New Energy and Industrial Technology Development
Organization (NEDO) under the Ministry of Economy, Trade and Industry (METI).
References:
[1] K. Arafune, T. Sasaki, F. Wakabayashi, Y. Terada, Y. Ohshita, M. Yamaguchi, Physica B 376-377
(2006) 236.
[2] K. Jiptner, M. Fukuzawa,Y.Miyamura, H.Harada, T.Sekiguchi, Jpn. J. Appl. Phys. 52 (2013)
(065501-1).
[3] B. Gao, S. Nakano, H. Harada, Y. Miyamura, K. Kakimoto, Cryst. Growth Des 13 (2013) 2661.
[4] B. Gao, K. Jiptner, S. Nakano, H. Harada, Y. Miyamura, T.Sekiguchi, K. Kakimoto, J. Cryst. Growth,
411 (2015) 49.
Numerical Modeling of Titanium Distribution in Sapphire Crystals Grown by
the Kyropoulos Method
Carmen Stelian*1, Gourav Sen1, Nicolas Barthalay2, Thierry Duffar1
1
SIMAP-EPM, 1340 Rue de la Piscine, BP 75, F-38402 Saint Martin d’Hères (France)
2
Le Rubis SA, BP 16, 38560 Jarrie Grenoble (France)
Sapphire crystals grown by using the Kyropoulos method excel the competition in structural quality, size
and production costs. Ti-doped sapphire crystals are of large interest as active media for the future high power
laser chains.
Large size Ti-doped sapphire crystals have been successfully grown by Le Rubis SA Company. The
optical characterization of 10 cm diameter crystals has shown a non-uniform radial distribution of titanium [1].
The analysis of Ti3+ ion radial distribution in several slices of 1 cm thickness, have shown that the
concentration is higher at the periphery of the crystal as compared to the central part of the ingot, which has a
nearly uniform composition.
In the present work, a transient model has been developed in order to simulate the heat, momentum and
species transport during the growth of Ti-doped sapphire crystals by Kyropoulos method. The modeling is
performed in two steps. First, a global model is used to simulate the heat exchanges in the whole furnace.
Then, the temperature distribution carried out from the global simulation is used as thermal boundary condition
for modeling the solidification process in an axi-symmetric domain containing the sample and the crucible. The
transient computations show an unsteady flow generated by the strong interaction between the convection and
the thermal field. The flow pattern, which is changing periodically in time, is characterized by two main flow
cells. The first one is located near the symmetry axis, with the fluid moving down to the bottom of the crucible.
The second vortex has a lower intensity and is located near the free surface of the melt. The shape of the
isotherms is strongly affected by the buoyancy convection. The intense flow occurring at the symmetry axis
influences the crystal-melt interface, which becomes conically shaped a short time after starting the growth
process.
Computations of Ti distribution show a uniform composition of the melt due to the intense convective
mixing. The non-uniform radial profile measured in the grown ingot is explained by the conical shape of the
crystal-melt interface. The lateral part of the sample is solidified at a later stage of the growth process, as
compared to the central part. At that time, the concentration of titanium in the liquid increases, due to the
chemical segregation at the growth interface. That explains the radial U-shaped profile with higher Ti
concentration at the crystal periphery.
References:
[1] Nehari A., Brenier A., Panzer G., Lebbou K., Godfroy J., Labor S., Legal H., Cheriaux G.,
Chambaret J.P., Duffar T., Moncorge R., Cryst. Growth Des. 11 (2011) 445.
Evolution of grains during solidification of silicon – attempts of numerical
simulations for an understanding
Miller Wolfram*1, Popescu Alexandra2
1
Leibniz Institute for Crystal Growth (IKZ), Max-Born-Str. 2, 12489 Berlin (Germany)
Faculty of Physics, West University of Timisoara, Bd. v. Parvan 4, 300223 Timisoara
2
Despite the great importance of direct solidification of silicon for application in photovoltaics
there is still a lack of detailed understanding of the evolution of grains, grain boundaries and
dislocations. Different attempts have been made to tackle the problem by numerical simulations.
We present calculations on the mesoscopic level by means of a phase field method. The influence
of growth parameters as cooling rate and temperature gradient will be discussed for particular
examples. This includes some remarks on the growth kinetics of {111} facets and interfacial
energies between melt and crystal as well as between grains of different orientations. In the
mesoscopic calculations we mimic the typical process by a fixed temperature at the boundary of the
melt, decreasing in time by a given cooling rate [1]. On the boundary of the solid we apply a heat
flux removing the incoming heat by the initial temperature gradient in the melt and the heat
produced by solidification defined by the initial temperature gradient and he given cooling rate.
These mesoscopic calculations will be set into the context with macroscopic computations and
an outlook will be given.
References:
[1] W. Miller, A. Popescu, C. Cantù, J. Crystal Growth, 385 (2014) 127
Analytic scaling function for size distributions of 2D surface islands
V. G. Dubrovskii1-3, N. V. Sibirev1, Yu. S. Berdnikov1
1
2
St. Petersburg Academic University, Khlopina 8/3, 194021, St. Petersburg, Russia
Ioffe Physical technical Institute RAS, Politekhnicheskaya 26, 194021, St. Petersburg, Russia
3
ITMO University, Kronverkskiy pr. 49, 197101 St. Petersburg, Russia
Modeling of island size distributions (ISDs) is paramount both in terms of pure understanding of physical
properties of irreversible systems and of progress toward tailoring the island morphology. One of the most
interesting features of the ISDs is the scaling property suggesting that, in the limit of high ratios of the adatom
diffusion constant over the deposition rate, the ISD scales as n( x,  s , )  [ /  s 2 ] f ( x) . Here,  s 
and  are the time-dependent mean size and coverage, respectively, and f (x) is a universal scaling function
of the scaled size s /  s  .
We obtain an explicit solution for the island size distribution described by the rate equations for irreversible
growth with the capture rates  s ()   p ( a  s  1) for all sizes s  1 . Our solution has the form [1]
f ( x)  ( p  1)b p 1
(a  p) p
x  (bx, a  p ) ,
(a  1)
with b  (a  1)( p  1) /( p  2) ,  as the gamma-function and  as the regularized incomplete gammafunction [Fig. 1 (a)]. This function depends on the two parameters a and p, is monotonically decreasing at
p  0 , monomodal at p  0 and is capable of describing a rich variety of distribution shapes [Fig. 1 (b)].
(a)
(b)
Fig. 1. (a) Collapse of the numerical solutions at a  2 , p  0.5 and different times
(symbols) to the analytic scaling function (line); (b) Scaling function at p  1 / 2 and
different a .
The obtained results suggest that the scaling features of the ISDs are closely related to the size-linearity of the
capture rates. A simple analytic scaling is obtained here rigorously and helps to gain a better theoretical
understanding of possible origins of the scaling behavior. We also consider how our results fit the experimental
size distributions of Ga, In, Al and Mn linear atomic chains on Si(100)-2×1 surfaces [2].
References
[1] V.G. Dubrovskii and N.V. Sibirev, Phys. Rev. E 91 (2015) 042408.
[2] V.G. Dubrovskii and Yu.S. Berdnikov, J. Chem. Phys. 142 (2015) 124110.
On Modeling Interface Attachment Kinetics in Melt and Solution Growth
Systems
Oleg Weinstein1, Oren Bass1, Alexander Virozub1, Andrew Yeckel2, Wolfram Miller3, Jeffrey J. Derby2,
Simon Brandon*1
1
2
Dept. of Chemical Engineering, Technion, Haifa (Israel)
Dept. of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN (USA)
3
Simulation & Characterization, Leibniz Institute for Crystal Growth, Berlin (Germany)
* [email protected]
Interface attachment kinetics obviously always takes place at fluid/crystal interfaces during
crystal growth from a fluid phase. However, when modeling crystal growth processes it is not
always necessary to explicitly account for this phenomenon. In such situations the departure from
equilibrium at the growing interface can be neglected and its shape and position can be tracked
based on the analysis of transport phenomena and, when relevant, capillarity. This is often the case
in many melt growth systems in which the melt/crystal interface position typically coincides with
the melting-point temperature of the growing crystal. At the same time, certain melt growth systems
and most large-scale solution growth processes do exhibit evidence of the importance of interface
attachment kinetics in determining growth characteristics. This evidence is typically provided in the
form of faceting along the evolving fluid/crystal interfaces. Such facets are indicative of relatively
slow kinetics (in particular crystallographic orientations) requiring a significant departure from
equilibrium to sustain growth. Modeling growth of such systems requires the combined analysis of
transport phenomena, interface attachment kinetics and (when necessary) capillarity. The strong
anisotropy in growth kinetics, the related combined action of different growth mechanisms, and the
significant difference in time scales associated with relevant phenomena, make it particularly
challenging to model such systems.
In this contribution we will review our methods for modeling interface attachment kinetics in
melt and solution growth systems and show sample calculations with specific reference to a number
of important questions. These include the physics occurring at junctions between different surfaces
in melt-growth systems, the dynamics associated with sudden changes in growth mechanisms, the
interaction between anisotropic capillarity along the triple phase line and anisotropy (i.e. faceting)
due to attachment kinetics along the melt/crystal interface in Czochralski growth systems, the
physics of step sources and sinks at edges joining faces in solution growth systems and issues
related to differences in time scales associated with interface attachment kinetics and transport
phenomena.
Tailoring crystal growth more and more quantitatively via multiscale simulations
Prof. Dr.-Ing. Heike Emmerich1
1University Bayreuth, Universitätsstraße 30, 95440 Bayreuth (Germany)
Due to the global market situation, the world wide materials industries experiences a strong
pressure to develop advanced materials with special purpose properties at successively decreasing
time scales. Thus there is a steadily growing importance of systematic materials development
supported by computer simulation methods. Indeed, materials science simulation methods have
matured to this point: There has been a growing impact on materials development by modeling and
simulation at all relevant length scales (quantum-mechanical, atomic, mesoscopic, continuum).
Dedicated methods have been designed for each length scale, as well as methods to address scalebridging phenomena (multi-scale modeling).
The talk gives an overview how these methods can contribute more and more quantitatively to main
features of bulk as well as epitaxial growth with a strong focus on nucleation and successive
microstructure evolution and what kind of insight is possible at what kind of computational price.
The methodological focus is on a synergetic combination of DFT, KMC, phase-field crystal and
phase-field methods as well as efficient experimental calibration and comparison. Precise scenario,
insight-gained tied to necessary model and simulation advances are depicted for Si as well as AlN
growth.
Phase field simulations of particle capture during directional solidification of
silicon for solar cells
Emmerich Heike Emmerich1, Hörstermann Henning Hörstermann*1, Kundin Julia Kundin1, Friedrich
Jochen Friedrich2, Azizi Maral Azizi2, Reimann Christian Reimann2, Cröll Arne Cröll3, Jauß Thomas Jauß3,
Sorgenfrei Tina Sorgenfrei3
1
University of Bayreuth, Chair of Material and Process Simulations, Bayreuth (Germany)
2
Fraunhofer IISB, Erlangen (Germany)
3
University of Freiburg, Institute for Geosciences, Freiburg (Germany)
We study the interaction between the solidification front and the SiC particles present in the
melt during the growth process of silicon for solar cells. These and other particles can form in the
melt as a result of contamination. Usually, particles of a given size are pushed in front of the
solidification front for growth velocities below a critical value and are incorporated into the crystal
for growth velocities exceeding this value. During the growth of silicon crystals for solar cells,
process parameters should be selected in a way that most of the particles are pushed as captured
particles reduce the efficiency of the solar cell.
In order to describe the relationship between critical particle size and critical growth
velocity, existing theoretical models for particle capture usually assume an equilibrium of all forces
acting on the particle while moving with the same velocity as the solidification front (see e.g. [1]
and references therein). For silicon carbide particle in silicon, these models predict significantly
higher critical particle sizes than observed in experiments [2]. Furthermore, experiments suggest
that the relation between critical growth velocity and particle size can not be described by a power
law [3], as most of the theoretical models predict.
In addition to adapting existing theories [4,5] in order to explain these deviations, we use a
phase-field model to systematically study the influence of different choices for the repulsive
interactions between particle and solidification front, partial engulfment of the particle by the
solidification front, non-spherical particle shapes, and different capture scenarios on the predicted
critical particle size and its dependence on the growth velocity [6]. We find that the critical particle
size is often substantially dependent on the shape and surface roughness of the particles: the mass of
the critical particle, for example, can change by a factor of five if the particle's aspect ratio changes
by merely 3%. In comparison, the predictions from models that use different repulsive forces and
capture scenarios but predict the same critical particle size at one growth velocity, for its value at a
growth velocity twice as high typically differ by less than 10%.
We assess the implications of these results on the typical approach to compare the
predictions for critical growth velocities for particles of different size with experimental results in
order to test the validity of a theoretical model. We propose how a better differentiation between
models can be achieved.
References:
[1] R. Asthana and S. Tewari, Journal of materials science, 28 (1993) pp. 5414–5425
[2] A. K. Søiland, Silicon for solar cells, PhD thesis, NTNU, 2004.
[3] J.J. Derby, Oral presentation, CSSC-8, Bamberg, May 5-8, 2015
[4] A.V. Catalina, S. Mukherjee, D.M. Stefanescu, Metall. Mater. Trans. A 31 (2000) pp. 2559–2568, 2000
[5] J. Kundin et al., in preparation
[6] H. Hörstermann et al., in preparation
Phase-field study of morphological evolution during directional solidification:
influence of temperature gradient and convection
Ankit, Kumar*1,2, Selzer, Michael1,2, Bhattacharya, Avisor1,2, Nestler, Britta1,2
1
Institute of Applied Materials (IAM), Karlsruhe Institute of Technology,
Haid-und-Neu Str. 7, 76131 Karlsruhe (Germany)
2
Institute of Materials and Processes (IMP), Karlsruhe University of Applied Sciences,
Moltkestr. 30, 76133 Karlsruhe (Germany)
In the past, phase-field method has been applied to address various aspects of topological
evolution accompanying solidification [1,2] and precipitation [3,4,5]. Particularly the solidification
of alloys is known to yield patterns of great geometrical complexity, such as dendrites, cells, or
faceted morphologies. In the present work, we employ the multiphase-field model [1] to study the
influence of applied temperature gradient on the polycrystalline evolution (Fig. 1a) in binary alloys.
Using faceted anisotropic interfacial energy and kinetic functions, the numerical simulations are
carried in the parameter space of practical interest and compared with experimental findings. Next,
we discuss the influence of convective fluid on the morphological evolution and growth
competition due to the misorientation (w.r.t most-preferred-orientation) amongst neighboring
crystals.
In the arena of dendritic solidification, it is well known that the fluid flow modifies the
convective heat transport away from the dendrite tip. In absence of convective flow, a small
perturbation of the preexisting solid layer evolves as instability. As a result of strong solute
segregation adjacent to the primary arm, new instabilities, similar to damped wave patterns, evolve
as shown in Fig. 2c. Repeated nucleation adjacent to primary instability is also seen for the case of
needle-like growth in diffusion-controlled regime (Fig. 2b). Finally, it is shown that the imposed
fluid flow curtails the nucleation of such new instabilities as the primary arm evolves (Fig. 2d).
Figure 1. Phase-field simulation of directional (a) polycrystalline (b) needle-like and (c) dendritic growth. (d)
Same as (c) with imposed fluid flow.
References:
[1] Nestler B., Garcke H., Stinner B., Phys. Rev. E, 71(2005) 041609.
[2] Selzer M., Jainta M., Nestler B., Phys. Status Solidi B, 246(2009) 1197-1205.
[3] Ankit K., Nestler B., Selzer M., Reichardt M., Contrib. Mineral. Petrol., 166(2013) 1709-1723.
[4] Ankit K., Urai J., Nestler B., J. Geophys. Res.-Sol. Ea. (2015) doi: 10.1002/2015JB011934.
[5] Ankit K., Selzer M., Hilgers C., Nestler B., J. Petrol. Sc. Res., (2015) in press.
Phase-Field Crystal Modeling of Heterogeneous Nucleation and Heteroepitaxy
László Gránásy1,2,*, Frigyes Podmaniczky1, Gyula I. Tóth1,3,György Tegze1, Tamás Pusztai1
1
Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, POB 49, Budapest (Hungary)
Brunel Centre for Advanced Solidification Technology, Brunel University, Middlesex UB8 3PH, Uxbridge (U.K.)
3
Department of Physics and Technology, University of Bergen, 55 Allégaten, 5007 Bergen (Norway)
2
Crystallization of supersaturated liquids usually starts by epitaxial growth or by heterogeneous
nucleation on foreign surfaces. Herein, we review recent advances made in modeling heteroepitaxy
and heterogeneous nucleation on flat/modulated surfaces and nanoparticles within the framework of
a simple dynamical density functional theory, known as the Phase-Field Crystal (PFC) model [1-3].
The crystalline substrate is represented by spatially confined periodic potentials. It will be shown
that the contact angle and the nucleation barrier are non-monotonous functions of the lattice
mismatch between the substrate and the crystalline phase. In continuous cooling studies for
substrates with lattice mismatch, we recover qualitatively the Matthews–Blakeslee mechanism of
stress release via the misfit dislocations. The simulations performed for particle-induced freezing
will be confronted with recent analytical results, exploring thus the validity range of the latter. It
will be demonstrated that time-dependent studies are essential, as investigations based on
equilibrium properties often cannot identify the preferred nucleation pathways. Results obtained
with diffusive dynamics [1-3] (applicable to colloids) and with a hydrodynamic extension of the
PFC theory [4] (for simple liquids) will be compared. Modeling of these phenomena is essential for
designing materials on the basis of controlled nucleation and/or nano-patterning.
Figure 1. Island formation of 2D hexagonal structure of faceted crystal habit on a square-lattice substrate in the 2D PFC
model for a lattice mismatch of 14%. On the right the Voronoi polyhedron map is shown: Colors grey, blue, yellow, and
red stand for nearest neighbor numbers of 4, 5, 6, and 7, respectively.
References:
[1] Elder K.R., Katakowski K., Haataja M., Grant M., Physical Review Letters 88 (2002), 245701.
[2] Emmerich H., Löwen H., Wittkowski R., Gruhn T., Tóth G.I., Tegze G., Gránásy L., Advances in
Physics 61 (2012) 665.
[3] Tóth G.I., Tegze G., Pusztai T., Gránásy L., Physical Review Letters 108 (2012), 025502.
[4] Tóth G.I., Gránásy L., Tegze G., Journal of Physics: Condensed Matter 26 (2014) 055001.
Phase-field Modelling of Spiraling Ternary Eutectic Dendrites
László Rátkai1,*, Tamás Pusztai,1 Attila Szállás,1 László Gránásy1,2
1
Institute of Solid State Physics and Optics, Wigner Research Centre for Physics, POB 49, Budapest (Hungary)
Brunel Centre for Advanced Solidification Technology, Brunel University, Middlesex UB8 3PH, Uxbridge (U.K.)
2
Extending previous work [1], we have studied the formation of eutectic dendrites in a model
ternary system within the framework of the phase-field theory. We have mapped out the domain in
which two-phase dendritic structures grow. With increasing pulling velocity, the following
sequence of growth morphologies is observed: flat front lamellae  eutectic colonies  eutectic
dendrites  dendrites with target pattern  partitionless dendrites  partitionless flat front (Figure
1). We confirm that the two-phase and one-phase dendrites have similar forms, and display a
similar scaling of the dendrite tip radius with the interface free energy. It is also found that the
possible eutectic patterns include the target pattern, and single- and multi-arm spirals, of which the
thermal fluctuations choose. The most probable number of spiral arms increases with increasing tip
radius and with decreasing kinetic anisotropy. Our numerical simulations confirm that in agreement
with the assumptions of a recent analysis of two-phase dendrites [2], the Jackson-Hunt scaling of
the eutectic wavelength with pulling velocity is obeyed in the parameter domain explored, and that
the natural eutectic wavelength is proportional to the tip radius of the two-phase dendrites. Finally,
we find that it is very difficult/virtually impossible to form spiraling two-phase dendrites without
anisotropy, an observation that seems to contradict the expectations outlined in Ref. [2]. Yet, it
cannot be excluded, that in isotropic systems two-phase dendrites are rare events difficult to observe
in simulations.
Figure 1. Solidification morphology and pattern formation as a function of dimensionless pulling velocity. The c1 and c2rich solid solutions are coloured red and yellow, respectively, whereas the liquid is transparent, and purple stands for c1
 c2. The front view (top row), the longitudinal section (central row) and transverse cross sections (bottom row) are
displayed.
References:
[1] Pusztai T., Rátkai L., Szállás A., Gránásy L., Phys. Rev. E 87 (2013) 032402.
[2] Akamatsu S., Bottin-Rousseau S., Faivre G., Brener E.A., Phys. Rev. Lett. 112 (2014) 105502.
Time Evolution of 2D Cellular Automata with “Crystal Growth” Rules
Alexander Kolevski1, Hristina Popova2, Georgi As. Georgiev3, Vesselin Tonchev2
1
2
Alexandrovska University Hospital, 1 Georgi Sofijski str., Sofia (Bulgaria)
Institute of Physical Chemistry, Bulgarian Academy of Sciences, 11 Acad. Georgi Bonchev str., Sofia (Bulgaria)
3
Faculty of Biology, University of Sofia “St. Kliment Ohridski”, 8 Dragan Tsankov blvd.. Sofia (Bulgaria)
With crystal growth (CG) in complex environments in mind (protein crystallization, bio-film
drying patterns) we build a set of 2D Cellular Automata (CA) with each cell having three possible
states: 0, 1(single atom) and 2 (crystalline). The state of a cell in time t=i+1 is determined by the
states of five cells in t=i (the cell itself and its nearest neighbors). The number of rules for these CA
is 3^(3^5), thus the common notions of CG are used for rule selection. The general (batch
crystallization) setup of our simulations is: define the rule - how 1-cell transforms in 2-cell; create a
random subset of 1-cells, others are 0 with no further addition of 1-cells; update the cells using the
rule; attempt exchanging the values of all 1-cells with a neighbor in state 0; repeat until all 1-cells
“crystallize” (turn in 2-cells). One “hopping” and one “growth” update (see [1]) form one time step,
thus permitting to monitor the evolution of the number of 2-cells.
We start with the simplest rule – every time a cell in state 1 has a neighbor in state 1 or 2 it also
turns in state 2 (critical nucleus of two atoms). The time evolution is of Kolmogorov-Avrami (KA)
type [2], the parameters change with the initial number of 1-cells. Increasing the number of
necessary non-zero neighbors changes the range of parameter values in the KA equation.
Next we study DLA CA populating the lattice with 1-cells and placing a 2-cell in the center
while forbidding further nucleation (Figure 1a, in green). In one subset of the simulations we add
unidirectional bias – hops in right are with higher probability (Figure 1a, in red) than those in left.
Bias changes the canonical fractal dimension of 1.71, thus caution is needed when measuring fractal
dimensions in such cases. Time evolution of the crystalline phase is of logistic type but it has a
universal form (Figure 1b, inset). We conclude with even more complex automata to account for the
existence of more nuclei (double impulse technique).
Authors acknowledge the financial support from grant T02-8/121214. VT is grateful to Christo
Nanev and Isak Avramov for the numerous discussions.
Figure 1. Cellular Automaton with “DLA” rule (pbc hold), initial occupation 10%: (a) bias modifies
the fractal dimension of 1.71 in a complex manner; (b) time evolution is also affected, both
dependencies are collapsed onto an universal logistic curve one with K=6.3 (inset).
References:
[1] D’Souza R., Margolus N., Physical Review E, 60 (1999) 264.
[2] Avramov I., Physica A, 379 (2007) 615.
POSTER
S02-P01
Atomic scale design of epitaxial interfaces: clusters, stripes and nanowires
Michail Michailov and Bogdan Ranguelov
Institute of Physical Chemistry, Bulgarian Academy of Sciences, Sofia 1113 Bulgaria
The present lecture outlines an important area in the application of computer modelling to
crystal growth, surface and interface phenomena. Being relevant to the fundamental physical
problem of competing atomic interactions in systems with reduced dimensionality, these
phenomena attract special academic attention. On the other hand, detailed knowledge of the fine
atomic structure of interfaces is essential for understanding and solving a large number of practical
problems in contemporary material science. Typical examples are formation of nanoscale surface
patterns, two-dimensional superlattices, atomic intermixing at epitaxial interface, transport
phenomena of atoms and atomic clusters, structure and stability of quantum wires on surfaces. In
the present report we discuss a variety of diffusion mechanisms that control nanoscale interface
patterning by surface-confined atomic exchange, formation of alloyed atomic stripes and islands,
relaxation of pure and alloyed atomic terraces, migration of clusters and their stability in external
field. The computational Monte Carlo model refines important details of diffusion of adatoms and
clusters accounting for the energy barriers at specific atomic sites: smooth domains, terraces, steps
and kinks. This systematization imply classification order of surface alloying: blocked, incomplete,
and complete. The diffusion kinetics, integrity and decomposition of atomic islands in an external
field are considered in detail and assigned to specific energy regions depending on the cluster
stability in mass transport processes. Step roughening impact on atomic step permeability
phenomena is discussed. The presented ensemble of diffusion scenarios opens a way for nanoscale
surface design towards regular atomic interface patterns with exotic physical features. Finally, the
lecture discusses the problem of thermal stability of metal nanowires on crystal surfaces. The
spontaneous breakdown of free-standing or interface-located monatomic nanowires is considered in
a model involving consecutive three-step mechanism for nanowire rupture, grounded on formation
of active atoms, atomic vacancies and vacancy clusters. The present report also demonstrates the
extended capability of atomistic models in computer simulations to unravel simultaneously acting
effects, to distinguish between them, and finally to evaluate their specific contribution to
experimentally observed complex physical phenomena.
References:
[1] M. Michailov “Classification Order of Surface-Confined Intermixing at Epitaxial Interface” in: “Nanophenomena at
Surfaces: Fundamentals of Exotic Condensed Matter Properties”, Springer Series in Surface Science 47, Chapter 6, p.
145-168, M. Michailov (Ed), Springer, Berlin Heidelberg 2011
[2] M. Michailov “Computational Study of Stripe Alloy Formation on Stepped Surfaces” Phys. Rev. B, 80, p. 035425
(2009)
[3] M. Michailov, M. Vladkov “Surface Diffusion of Pb Clusters on Cu(111) Influenced by Size Dependent ClusterSubstrate Misfit: Monte Carlo Tight Binding Simulation Model” Surface Science 601, 18, p.3912 (2007)
[4] B. Ranguelov and M. Michailov “Atomic diffusion on vicinal surfaces: step roughening impact on step
permeability” Journal of Phys. CS 558 (2014) 012004
[5] M. Michailov, D. Kashchiev “Monatomic metal nanowires: “Rupture kinetics and mean lifetime”, Physica E 70
(2015) p.21–27
S02-P02
A single-domain approach to simulate the effect of convective flow on the mushy
zone structure in Czochralski growth of semitransparent oxide crystal
Reza Faiez*, Majid Mashhoudi, Yazdan Rezaei
1
Solid State Lasers Department, Laser & Optics Research School, Tehran P.O. Box 11365-8486, Iran
In the growth model considered, the two-dimensional convective flow in GGG melt (Pr=4.69) is
characterized by Ra=5.353×103 ΔTmax , Ma=2.742×102 ΔTmax, and Re=127.12Ω (rad/s) where 0.5
≤Ω (rad/s)≤3.0 is the crystal (rx = 30mm) rotation rate and the applied ∆Tmax=67K ensures the
growth at the tri-junction point. Both the crystal and melt have the same optical properties (n=1.8,
a=258 m-1) and discrete ordinates method was used to estimate the radiative heat flux in the
equation of energy. The phase field method was used to solve the phase change problem with
convetion. This method is based on a single-domain approach where a system of momentum and
energy equation is solved in the entire physical domain. For the cases with Ω≤2.0, the fluid motion
within the mushy zone is dominated by the buoyancy and thermocapillary forces ( Ur<0). The radial
velocity sign was changed when the rotation rate slightly increased to Ω=2.3. This can be infered
that, in the cases with Ω≥2.3 the rotationally driven convection plays a predominant role inside the
mushy region. As well, the ratio between the vertical and horizontal temprature gradient beneath the
zone, gz/gr found to be decreased to the values smaller than unity for the cases with Ω≥2.3, at
which the shape of mushy region was largely modified. This abrupt deformation of the mushy zone
found to be correlated with a baroclinic instability in the fluid resulting in cold plumes detaching
from the crystal and desending towards the crucible bottom. It was shown that, increasing Ω, the
gradiant Richardson number, Rig increases and the thermal Rossby number, RoT decreases. The
linear analysis predicts the onset of geostrophic instability when Bu≤0.58. This condition was
satisfied for Ω≥2.3. Remarkably, in this model, the Burgers number is very close to its critical value
(Bu*=0.58), when Ω=2.3 as shown in figure 1.
2
Figure 1. The dimensionless parametes, Rig, Bu, RoT and Gr/Re each as a function of the
rotationally-driven flow intensity,
Rerx2 /
where
Bu [( N /2)( hc / rc )]2 , RoT  g l ( T / z ) hc2 / 2 ( rc rx )2
Gr  g l T max rc3 / 2
,
Ri g  N 2 /( u r / z )2
and N is the buoyancy frequency.
,
S02-P03
Modeling of patterns by the phase field crystal method in three dimensions
Ilya Starodumov*1, Jesus Bueno2, Hector Gomez2, Peter Galenko3, Dmitri Alexandrov1
1
Laboratory of Multi-Scale Mathematical Modelling. Department of Mathematical Physics. Ural Federal University,
620000, Ekaterinburg (Russian Federation)
2
Department of Mathematical Methods. University of A Coruña. Campus de Elviña, 15192, A Coruña (Spain)
3
Friedrich-Schiller-Universität Jena, Physikalisch-Astronomische Fakultät, D-07737 Jena (Germany)
The phase-field crystal model (PFC model) is a continuum model which describes processes on
atomic length scales and patterns on the nano- and micro-length scales [1,2]. This model is
characterized by a conserved field which is related to the local atomic number density, such that it is
spatially periodic in the solid phase and constant in the liquid phase. The PFC model provides an
efficient tool for simulating the ordering of nanoscale structures on micron length scales, liquidsolid transitions, dislocation motion and plasticity, glass formation and foams, epitaxial growth,
grain boundary premelting, crack propagation, surface reconstructions, grain boundary energies,
dynamics of colloidal systems, and polymers [3].
In this study, we consider the solidification of a metastable and unstable liquid state as
described by the three-dimensional PFC model. The phase transition from the metastable state to
the stable one occurs by overcoming the energy barrier which is usually necessary for the
emergence of a new phase. Contrary to that, a transition from the unstable state proceeds without
energy barrier that is usually evolves by fluctuation mechanism. Both of these transitions are
modeled numerically for obtaining various crystalline patterns emerging from the liquid.
For the numerical solution of the PFC model presented in Ref. [4], we have obtained a scheme
-continuous functions
based on isogeometric analysis (IGA) which allows us to generate the
required for the numerical discretization. For integration in time, the developed numerical algorithm
uses the generalized- method. The algorithm has been realized in C-language code. We have used
the wide spread frameworks PetIGA and PETSc which implement NURBS-based Galerkin finite
element method. Using PETSc tools has allowed us to customize code in effective parallelization
mode. We have tested our program on more than 200 CPU cores as well as 10 GPU cores and in all
cases we have observed productivity of calculation proportional to the increase of the number of
cores.
Using the developed program code, various crystal patterns in three spatial dimensions were
obtained. The structure diagram has been created in coordinates “driving force-average atomic
density” and compared with the diagram theoretically calculated in Ref. [5]. The developed
program code can be applied for the problem of selection of the lattice parameter at the front of the
periodic new phase invading homogeneous liquid or other periodic crystal lattice. The theory and
program code were developed for small and large driving force of liquid-solid or solid-state
transformations.
References:
[1] K.R. Elder and M. Grant, Phys. Rev. E 70, 051605 (2004).
[2] K.R. Elder, N. Provatas, J. Berry, P. Stefanovic, and M. Grant, Phys. Rev. B 75, 064107 (2007).
[3] H. Emmerich, H. Löwen, R. Wittkowski, T. Gruhn, G. I. Toth, G. Tegze, L. Granasy, Advances
in Physics 61, 665 (2012).
[4] P.K. Galenko, H. Gomez, N.V. Kropotin, K.R. Elder, Phys. Rev. E 88, 013310 (2013).
[5] A. Jaatinen, T. Ala-Nissila, Journal of Physics: Condensed Matter 22(20), 205402 (2010).
S02-P04
Kinetic Monte Carlo simulations of vicinal GaN(000-1) surface evolution during
N-rich growth
Filip Krzyżewski*1, Magdalena A. Załuska-Kotur*1
1
Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, Warsaw (Poland)
We use 2-component kinetic Monte Carlo model to study vicinal GaN(000-1) surface patterns.
The model was recently used in the analysis of wurtzite crystals surface evolution [1]. In this work
we apply it to the gallium nitride N face. Hence we improved the previous model [2-5], which was
limited due to the control of only one kind of atoms forming GaN crystals. New model allows for
the full control on fluxes and diffusion of all atoms.
We study the influence of miscut angle, temperature and nitrogen supersaturation on the
character of the surface structures that emerge during crystal growth.
Different surface patterns were obtained. At steep surface with 4º miscut smooth surface with
straight, parallel steps is observed. Decrease of miscut angle to 2º leads to surface roughening and a
mixture of bunches and meanders emerges [1]. Numerical results agree with experimental plasmaassisted MBE (PAMBE) growth of GaN(000-1) [6].
PAMBE experiments, in low temperatures, show step flow growth mode [7]. In such a case
speed of adatom diffusion plays an important role in the surface evolution process. When the
diffusion is slow in comparison to the terrace width, time of particle wandering at the surface is
long. Adatoms can easily encounter other atoms in their route to step edges. It leads to two
dimensional nucleation on the surface. Islands which emerge in such a way are incorporated by the
steps which move forward. Processes of island nucleation and step movement lead to the emergence
of mixed bunched-meandered surface pattern. On the other hand, when the surface is steep, terraces
are narrow and time of adatom wandering on the surface is shorter. Particles attach to the steps
before they encounter other atoms. No 2D nucleation takes place and the system surface evolves to
the smooth pattern.
We show that increase of temperature or nitrogen flux reduces 2D nucleation at terraces. Hence
in such conditions, at low miscut obtained surfaces are smoother.
This work was supported by research grant from the National Science Centre (NCN) of Poland
(Grant NCN No. 2013/11/D/ST3/02700).
Figure 1. Results of the simulation at lower miscut 2º
Figure 2. Results of the simulation at higher miscut 4º
References:
[1] F. Krzyżewski and M. A. Załuska-Kotur J. Appl. Phys. 115, 213517 (2014)
[2] M. A. Załuska-Kotur, et al, Cryst. Growth & Design 13, 1006 (2013)
[3] M. A. Załuska-Kotur, F. Krzyżewski, S. Krukowski, Journal of Applied Physics, 109 (2011) 023515
[4] Ma.A. Załuska-Kotur, Fi.Krzyżewski, Journal of Applied Physics 111, 114311 (2012)
[5] M. A. Załuska-Kotur, F. Krzyżewski, S. Krukowski, J. Cryst. Growth 343 (2012) 138
[6]C. Cheze, et. al. Appl. Phys. Lett. 103, 071601 (2013)
[7] B. Heying, et al, J. Appl. Phys. 88, 1855 (2000)
S02-P05
Modeling of dendritic growth under earthly and reduced gravity conditions
P.K. Galenko*1, D.V. Alexandrov2, D.A. Danilov3, K. Reuther1, M. Rettenmayr1, D.M. Herlach4
1
3
K ARLSRUHE
F RIEDRICH S CHILLER U NIVERSITY , J ENA (G ERMANY )
2
Ural Federal University, Ekaterinburg (Russia)
I NSTITUTE OF T ECHNOLOGY , E GGENSTEIN -L EOPOLDSHAFEN (G ERMANY )
4
G ERMAN A EROSPACE C ENTER , C OLOGNE (G ERMANY )
A thermo-solutal problem of a free dendrite growing with high velocity under forced fluid flow is
considered analytically. The present theoretical model is based on the Oseen approximation for the
equations of fluid motion and takes into account small anisotropy of surface energy and atomic
kinetics. A criterion for the stable dendritic growth is derived from the solvability condition by the
method described in Refs [1,2]. This criterion generalizes the previous known results for the stable
growth of a dendritic crystal. Model predictions are compared with experimental data on crystal
growth kinetics in droplets processed in electromagnetic and electrostatic levitation facilities [3,4].
Developed theoretical and simulation methods are applied to crystallization of Ni-B, Cu-Zr and TiAl alloys under earthly and reduced gravity conditions. This work has been done under support
from German Research Foundation (DFG Project RE 1261/8-2), Russian Foundation for Basic
Research (RFBR Project No. 14-29-10282ofi_m) and by the DLR Space Management within
contract 50WM1140.
References:
[1] D.V. Alexandrov and P.K. Galenko, Phys. Rev. E 87, 062403 (2013).
[2] D.V. Alexandrov and P.K. Galenko, Physics-Uspekhi 57(8), 771 (2014).
[4] S. Binder, P.K. Galenko and D.M. Herlach, Phil. Mag. Lett. 93, 608 (2013).
[5] S. Binder, P.K. Galenko and D.M. Herlach, Journal of Applied 115, 053511 (2014).
S02-P06
Relationship between stability of facet surfaces and incorporation of zinc-blende
phase in InN during pressurized reactor MOVPE: A theoretical approach
Akira Kusaba*1, Yoshihiro Kangawa1, 2, Stanisław Krukowski3, Koichi Kakimoto1, 2
1
Dept. Aeronautics and Astronautics, Kyushu University, Fukuoka 819-0395 (Japan)
2
RIAM, Kyushu University, Fukuoka 816-8580 (Japan)
3
UNIPRESS, ul. Sokolowska 29/37, 01-142 Warsaw (Poland)
In-rich InGaN is a promising material for bright green and red LEDs. However, the increase in
In content tends to deteriorate the crystalline quality owing to the decrease in decomposition
temperature or the optimum growth temperature. Pressurized-reactor (PR) MOVPE, which enables
high-temperature film growth, is an efficient method for fabricating InGaN films of high crystalline
quality and high In composition. In case of [000-1] (-c) growth, however, it has been reported that
zinc-blende phase (ZB) whose growth islands have (1-1-1) facet incorporates into wurtzite phase
(WZ) whose growth islands have (1-100) facet depending on growth conditions of PR MOVPE.[1]
Our aim is the theoretical estimate of growth conditions when pure WZ phase grows.
First, we calculated the surface energies of ideal surfaces on (1-100) and (1-1-1) facet plane
based on the method that makes effective use of the symmetry of ZB structure.[2, 3] Then, we
calculated the difference in free energies between (A) the system consisting of the reconstructed
surface with adatoms and (B) the system consisting of an ideal surface and gas phase particles.[4]
Here, the total energies were obtained by DFT calculations and the entropy of gas phase particles as
function of T and p were obtained by quantum statistical mechanics. We regard the sum of surface
energy of ideal surface and free energy of reconstructed surface based on ideal surface as surface
energy of reconstructed surface.
Figure 1 shows the difference in surface energies between (1-100) and (1-1-1) facet surfaces,
i.e., σ(1-100)−σ(1-1-1). The growth conditions
of WZ (blue hexagon) and ZB (red square)[1]
are also shown in the figure. In this growth
regime, WZ becomes stable in the high
temperature and low In partial pressure region.
Conversely, difference in surface energies
between (1-100) and (1-1-1) becomes small
under low temperature and high In partial
pressure region. Moreover, σ(1-100) − σ(1-11) drastically increases near the boundary of
WZ/ZB mixture. These results suggest that the
probability of ZB incorporation increases with
decreasing difference in surface energies
between (1-100) and (1-1-1). Now, we are
investigating the surface phase diagram of
Figure 1. Difference in surface energies,
InN(0001) to understand the growth process
σ(1-100)−σ(1-1-1).
along [0001] (+c).
References:
[1] T. Kimura et al., Phys. Stat. Sol.C, 9 (2012) 654.
[2] C. E. Dreyer et al., Phys. Rev. B, 89 (2014) 081305.
[3] S. B. Zhang et al., Phys. Rev. Lett., 92 (2004) 086102.
[4] Y. Kangawa et al., Surf. Sci., 493 (2001) 178.
S02-P07
Study of the early stages of Calcium Phosphate nucleation in water by means of
ab Initio Molecular Dynamics
Mancardi Giulia*1, Terranova Umberto1, De Leeuw Nora2
1
University College London, 20, Gordon street, London WC1H 0AJ (United Kingdom)
2
Cardiff University, Park Place, Cardiff CF10 3AT, (United Kingdom)
Amorphous Calcium Phosphate (ACP) is the precursor phase of apatite crystals in bone and
tooth tissues [1]. The formation of ACP is thought to proceed through a cluster-growth model [2].
The first step is the aggregation of prenucleation clusters (PNCs) [3], which are already present in
body fluids before nucleation. PNCs are in fact ion-association complexes, with formula
[Ca(HPO4)3]4-, which aggregate in solution. Above the solubility limit of ACP, they take up
calcium ions from solution to form insoluble post-nucleation clusters with formula [Ca2(HPO4)3]2that precipitate as ACP [3].
Here, we apply the umbrella sampling technique [4] to study the behaviour of PNCs in aqueous
solution. We have driven the system to the detachment of the (HPO4)2- group and its replacement by
water, along the reaction coordinate of the distance between the central Ca2+ ion and one
phosphorous atom out of the three coordinated (HPO4)2- groups (black dotted line in Figure 1).
Increasing systematically the targeted Ca-P equilibrium distance, we have performed a series of ab
initio molecular dynamics simulations, aimed at investigating the potential of mean force for the
phosphate-water exchange process. In addition, we discuss the effect of nearby Ca2+ counterions,
reported experimentally [3], to the free energy barrier.
Figure 1. Prenucleation cluster
References:
[1] Dey A., Bomans P.H.H., Muller F.A., Will J., Frederik P.M., de With G., Sommerdijk N.A.J.M., Nature
Materials, 9 (2010), 1010-1014
[2] Onuma K., Ito A., Chem. Mater., 10 (1998), 3346-3351
[3] Habraken W.J.E.M., Tao J., Brylka L.J., Friederich H., Bertinetti L., Schenk A.S., Verch A., Dmitrovic
V., Bomans P.H.H., Frederik P.M., Laven J., van der Schoot P., Aichmayer B., de With G., DeYoreo J.J.,
Sommerdijk N.A.J.M., Nat. Commun., 4 (2013), 1507
[4] Torrie G., Valleau J., Journal of Computational Physics, 23 (1977), 187-199
S02-P08
ON OBTAINING EQUILIBRIUM CRYSTAL SHAPE
UNDER NON-STATIONARY CONDITIONS
Gershanov Vladimir*1, Skorynina Alina1,Garmashov Sergey1
1
Southern Federal University, 5 Zorge, Rostov-on-Don (Russia)
The criterion for the equilibrium shape of a crystal contacting with its solution in some solvent
is the equality of the equilibrium concentrations in the liquid along the solid-liquid interface. The
equilibrium concentrations at all parts of the interface are determined only by the Gibbs-Thomson
effect, i.e. by the capillary effects. The equilibrium crystal shape is a particular case of the inverse
Gibbs-Thomson effect [1], when the mass transfer in the crystal-solution system proceeds under the
action of capillary forces under negative feedback conditions.
Generally, the mass transfer in the crystal-solution system takes place when both the interfacial
energy and interface kinetics are anisotropic. The higher value of the interfacial energy stimulates
obtaining the equilibrium shape, while interface kinetics and its anisotropy, in contrast, prevent this
process and lead to one of growth shapes. Therefore, in order to obtain the equilibrium shape, it is
important to eliminate the kinetic restrictions on the mass transfer at the solid-liquid interfaces. As
shown in [2], this is possible under non-stationary thermal conditions only. We consider the case of
the negative crystal, but, in our opinion, the result is also to be true for the case of the positive
crystal.
As shown in [2], the influence of interface kinetics can be eliminated at the rates of temperature
changes that generate supersaturations (at cooling) and undersaturations (at heating) in the solution
volume much larger than the critical supersaturations Ccr (undersaturations Cds) needed for the
crystallization (dissolution) processes at the singular interfaces. Under these conditions, the mass
transfer in the solution is restricted mainly by the diffusion process, and not by interface kinetics.
The complete disappearance of interface restrictions in this case is accompanied by another
nonlinear effect, namely, the effect of switching diffusive fluxes between the singular and nonsingular parts of the solid-liquid interface [2]. Depending on the form of the temperature
oscillations, this effect determines the ratio of the areas of the singular and nonsingular parts, and,
therefore, it is to be minimized for obtaining the equilibrium crystal shape. This is possible if the
saw-tooth temperature oscillations satisfy the following relation: ac / ah = Ccr / Cds, where ac (ah )
are the rates of cooling (heating).
We have simulated numerically the mass transfer under the non-stationary thermal conditions
for the case when the shape of the modeled negative crystal coincides with its equilibrium shape. It
is assumed that the negative crystal is a cylindrical liquid inclusion enclosed in a positive crystal,
and, therefore, the mass transfer in the liquid can be considered as two-dimensional. The simulation
has been performed using a computer program [3].
It has been shown that if the above-mentioned two criteria are met, the crystal shape remains in
equilibrium if it was in equilibrium in its initial state. Otherwise, if the initial shape was not in
equilibrium, the crystal obtains the equilibrium shape under the influence of the non-stationary
thermal conditions.
References:
[1] Gershanov V.Yu., Garmashov S.I. Technical Physics, 60 (2015) 61–65.
[2] Gershanov V.Yu., Garmashov S.I. Journal of Crystal Growth. 311 (2009) 2722–2730.
[3] Garmashov S.I., Gershanov V.Yu., Navigator in the World of Science and Education, 13 (2011) 63.
S02-P09
Working point of the EFG process
Laurent Carroz1, 2 and Thierry Duffar*3
1
SNECMA Villaroche, Rond-point René Ravaud, 77550 Réau, France
2
RSA, 380 Rue Rn 85 BP 16, 38560 Jarrie, France
3
SIMaP-EPM, UMR 5266 CNRS, 38402 Saint Martin d’Hères, France
The Edge-defined Film-fed Growth (EFG) technique allows growing shaped crystals directly
from the melt, then avoiding post machining operations that are costly and often generate defects in
the crystal. Initiated by Stepanov [1,2] cited in [3] and developed by Labelle [4], this technique,
considering its potential, received a great attention very early and quickly matured to industrial
process. Currently the most important for the industrial crystal grower is to find the best working
point of his process.
In this frame, a theoretical investigation of the EFG process working point based on the
meniscus height control is carried out. The link between the two control parameters, which are the
pulling rate and the upper die temperature, is analytically found from the thermal equilibrium at the
crystallization interface. Using the pressure equilibrium in the film and considering the viscous drag
and meniscus shape, the change in the meniscus height depending on the crystal radius is analyzed.
Limited to small crystal radii, an algebraic formulation of the temperature gradient at the interface is
established. Some die design parameters are taken into account and their impacts on the process
working point are discussed.
An example of the EFG process working point curves are given in figure 1 for different radii.
Figure 1. Example of EFG working points for crystallization of sapphire rods. V is the pulling rate, RC the
crystal radius and ΔT the overheating of the shaper, above the melting point.
References:
[1] A. V. Stepanov, Zh. Tekh. Fiz. 29 (1959), 382.
[2] A. V. Stepanov, The future of metalworking, Lenizdat, Leningrad 1963, In Russian.
[3] T. Duffar, (ed.), Crystal Growth Processes based on Capillarity: Czochralski, Floating Zone,
shaping and crucible techniques, J. Wiley-Blackwell, Chichester, UK, 2010.
[4] H. E. Labelle, Growth of inorganic filaments, US Patent #3471266, 1969.
S02-P11
Kinetic model of cement hydration with time-dependent rates
Valentini Luca1,2*, Artioli Gilberto1,2, Ferrari Giorgio3
1
Department of Geosciences, University of Padua, via Gradenigo 6, 35131 Padua (Italy)
2
CIRCe Centre, via Gradenigo 6, 35131 Padua (Italy)3
R&D Department, Mapei SpA, Via Cafiero 22, 20158 Milan (Italy)
Cement-based materials are of fundamental importance for modern society, especially for the
developing countries needing to tackle the issue of poor infrastructures. At present, the low cost and
broad availability of raw materials, as well as the relatively small environmental footprint per unit
volume produced, make it hardly imaginable to substitute cement with any other material. On the
other hand, the large demand and annual production result in significant issues related to CO2
emissions, mainly due to calcination of limestone, the primary raw material for the manufacture of
Portland cement. In order to meet the need of reducing greenhouse gas emissions without
hampering the worldwide availability of cement, it is fundamental to drive research towards
optimizing cement production and designing more sustainable cement-based materials, hence the
need of acquiring extensive knowledge about the processes that govern the chemistry of cement.
Cement hydration consists of a set of reactions by which anhydrous particles dissolve into ionic
species in solution that, upon reaching supersaturation with respect to a specific phase, precipitate
into hydrated solids, inducing the transformation of a fluid slurry into an elastic solid with high
mechanical strength. The main product of cement hydration is a poorly crystalline, nano-scale
calcium-silicate hydrate (commonly referred to as C-S-H in the field of cement chemistry) having a
pseudo-tobermoritic crystal structure. The precipitation of C-S-H consists of a first nucleation step,
during which new interfaces are formed in the pore solution (homogeneous nucleation) or at preexisting particle-water interfaces (heterogeneous nucleation). Nucleation is followed by the growth
or aggregation of the nuclei, as more ions are withdrawn from the pore solution and attached to the
surfaces of the newly formed species.
In this study, a kinetic model of the nucleation and growth of C-S-H is presented. The model is
based on the combination and generalization of the Johnson-Mehl-Avrami-Kolmogorov (JMAK)
and “boundary nucleation and growth” (BNG) models. Both the JMAK and BNG models had been
previously used to describe cement hydration kinetics by fitting calorimetric curves. The limitation
of this approach stems from the fact that constant rates of nucleation and growth are assumed.
However, the rate of cement dissolution-precipitation is controlled by the time-dependent
composition of the solution. Moreover, calorimetry only provides a picture of the overall kinetics,
without any information about the rates of dissolution-precipitation of the single phases. Here,
specific functions are used to describe the time-dependent rates of nucleation and growth. The
model is then used to fit the time distribution of the C-S-H mass fraction, obtained by in-situ X-ray
powder diffraction. The possibility of detecting changes in nucleation mechanisms, induced by
organic and inorganic additives, will be briefly discussed.
S02-P12
Crystal surface morphology as a consequence surface diffusion anisotropy
Magdalena A. Załuska-Kotur*, Filip Krzyżewski, Marcin Mińkowski
Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw, Poland
*[email protected]
Formation of various geometric patterns during crystal growth is a subject of continuous
interests of many researchers. It is important as an interesting example of far from equilibrium,
stationary process and because of practical applications in the crystal growth technology.
Temperature, surface miscut and flux of external particle are parameters that can be used to
control crystal growth in the experiment. On the microscopic base rate and character of diffusion
over terraces, along and across steps is very important phenomenon that determines final surface
morphology. Diffusion towards and across steps depends on so called Schwoebel barrier. During
crystal growth or sublimation, the height of barrier at step determines occurrence step bunching,
meandering and island step and positions. A novel variational analytic approach to the collective
diffusion will be presented and illustrated in various examples [1]. Highly anisotropic diffusion is
obtained for complex substrate's potential energy landscape or in the presence particle-particle
interactions [2,3]. We analyze particle movement in such conditions. In some situations Schwoebel
barrier at upper or lower step side is expected. As a consequence during crystal growth or
sublimation surface dynamics can change drastically as an answer to slight change of external
conditions. Results of calculations of diffusion coefficients for particles jumping over the surface
in different conditions are then applied in the kinetic Monte Carlo simulation of crystal growth
process. The kMC simulations are done for two different systems: GaN(0001) and 4H SiC(0001)
[4,5]. Within certain parameters steps move uniformly and stay straight during growth or
sublimation processes of both simulated crystals. We show that the presence of Schwoebel barrier
or strong diffusion anisotropy change this process into unstable one, being source of bunches,
meanders or both patterns emerging together. Phase diagram for all observed structure was found.
All surface patterns, emerging in the simulations, have their corresponding cases in the
experimental results [4]. The numerical models allow to observe how they develop and to study
their time evolution.
This work was supported by research grant from the National Science Centre (NCN) of Poland (Grant NCN
No. 2013/11/D/ST3/02700)
References:
[1] Magdalena A. Załuska-Kotur, Appl. Surf. Sci. 304 (2014) 122.
[2] M. Mińkowski, M.A. Załuska-Kotur , J. Stat. Mech. (2013) P05004
[3] M. Mińkowski, M.A. Załuska-Kotur, Phys. Rev.B 91 (2015) 075411
[4] M. A. Załuska-Kotur, Filip Krzyżewski, Stanisław Krukowski, Michał Leszczyński, Robert Czernecki ,
Cryst. Growth & Design 13 (2013) 1006
[5] Filip Krzyżewski and Magdalena A. Załuska–Kotur J. Appl. Phys. 115 (2014) 213517.
S02-P13
Monte Carlo simulation of island formation during GaAs(001) homoepitaxial
growth
Ageev Oleg Alekseevich, Solodovnik Maxim Sergeevich, Balakirev Sergey Vyacheslavovich*, Mikhaylin Ilya
Alekseevich
Institute of Nanotechnologies, Electronics, and Electronic Equipment Engineering of Southern Federal University,
2, Shevchenko St., Taganrog (Russian Federation)
We report kinetic Monte Carlo simulation of the initial stage of GaAs homoepitaxial growth on
the technologically important GaAs(001)-(2×4) reconstructed surface. The crystal is modeled as a
simple cubic solid-on-solid lattice. Arsenic dimer rows and missing trenches alternate across the
lattice. Atoms can interact with their nearest and next nearest neighbors. We take into account the
alteration of activation energy of each included diffusion process depending on the top-layer local
environment of a particle.
We observe that at temperature (T) of 580°C and growth rate (v) of 0.1 monolayer (ML) per
second the island density (N) is saturated after deposition of 0.06 ML GaAs. The simulation yields
N = 2·1012 cm-2, in agreement with experiments. Islands are preferentially formed in the trenches
and favor elongation along the [11 0] direction (Fig. 1).
The simulations were performed with the different growth conditions. It is known that N goes
down with temperature increase and rises with growth rate increase, and our simulations confirm
that. We also observe that N depends on V/III flux ratio. We find it to rise about twice with the
increase of V(As2)/III flux ratio from 3 to 40 either at lower temperature of 550°C (Fig. 2) or at
higher growth rate of 1 ML/S with the other conditions being equal. At lower growth rates and
higher temperatures N increases slightly with V/III ratio increase too. Whereas the growth
temperature decrease leads to the reduction of adatom diffusion coefficient, and the growth rate
increase enhances the probability of island formation in a random site, the flux ratio increase
intensifies the process of covering of Ga pairs formed in the most favorable sites. Thereby, the
growth process can be controlled by altering flux ratio without significant growth rate and
temperature changes which could induce defectiveness of the structure.
This work was supported by the Russian Science Foundation Grant No. 15-19-10006. The
results are obtained using the equipment of Common Use Center and Education and Research
Center "Nanotechnologies" of Southern Federal University.
Figure 1. Island morphology in a simulation area of
160 Å × 200 Å after deposition of 0.06 ML GaAs at T
= 580°C, v = 0.1 ML/s, V(As2)/III ratio = 10
Figure 2. Island density as a function of V(As2)/III flux
ratio after deposition of 0.06 ML GaAs at T = 550°C
(squares), T = 580°C (circles), T = 610°C (triangles); v =
0.1 ML/s
S02-P14
Mathematical modeling of the process of growing a single crystal CdTe 100 mm
by the Obreimov-Shubnikov method
Marina Pavlyuk*1, Ekaterina Sukhanova2, Marina Zykova2, Vladimir Kanevsky1, Igor Avetissov2
1
A.V.Shubnikov Institute of Crystallography RAS, Leninskii pr. 59, Moscow, (Russian)
D. Mendeleev University of Chemical Technology of Russia, Miusskaya pl. 9, Moscow, (Russia)
2
The growth kinetics is very important from the standpoint of improving of single crystal
technology and understanding of optical and structural defects formation in the crystal during the
growth process.
A direct study of the kinetics of CdTe crystal growth is very difficult. Since the growing crystal
is well shielded, the crystallization front (FC) in the melt and its visualization is not possible.
Sometimes, in practice the FC in defective single crystals can be determined by decorating using
microbubbles or by X-ray microanalysis, which allows displaying the components distribution
along the growth axis and ingot diameter. These data could be applied to prove the results of
numerical modeling of the growth process. The task of analysis of growth kinetics of large CdTe
single crystals grown by the Obreimov-Shubnikov technique was solved by the numerical
simulation using ANSYS 14.5 Fluent software. The calculation was carried out in three steps. At
the first step we have calculated a thermal profile of an empty shaft furnace (Figure 1a). At the
second step we simulated an internal space of the furnace with a quartz ampoule and a crucible with
melt inside the ampoule (1b). At the final step we calculated the melt flows in the crucible using the
thermal conditions obtained at the previous steps. The enthalpy model was used for crystallization
simulation. The simulation results are consistent with the growth experiment results, confirming the
adequacy of the numerical model.
This work was supported by the Russian Foundation for Basic Research RFBR (grant №14-02-31726 mol_а).
a)
b)
Figure 1. Temperature distribution: a) thermal profile in the empty shaft furnace filled by air and b) thermal
profile of the inner space of the furnace with the with a quartz ampoule and a crucible with melt inside the
ampoule
S02-P16
Experimentally Verified Numerical Simulation of Germanium Single Crystals
Grown by the AVC-AHP Technique
Yousefi L. Pouya*, Sheikhi Aidin, Mason Jeremy K., and Balikci Ercan
Department of Mechanical Engineering, Bogazici University, 34342 Bebek, Istanbul, Turkey
The axial heat processing (AHP) [1] and axial vibrational control (AVC) [2] techniques are
used to investigate the solid/liquid (s/l) interface shape and its morphological stability during the
antimony-doped germanium single crystal growth from the melt. To this end, three crystals each
have been grown by the AHP and AVC techniques with varying growth parameters that include the
melt height, pulling velocity, amplitude of vibration, and vibrational frequency.
In the AHP method, a baffle is immersed in the molten material inside a cylindrical crucible
that surrounded by a fixed furnace supplying a heat flux to the system. The baffle is used to reduce
the effective melt height, measured from the s/l interface to the baffle. The AVC method
additionally vibrates the submerged baffle axially to mix the melt in a controlled manner. Each
crystal is ground, polished and electro-etched in a H2O and Na2SO3 solution (79.2:1) [3] to visualize
the interface shape.
The AHP and AVC techniques have also been simulated using ANSYS Fluent software, with
the simulation parameters corresponding to the experimental growth parameters. The influence of
these parameters on the flow velocity map, temperature distribution in the melt, and s/l interface
shape of the growing crystal is analyzed. Since the experimental flow velocity of the Sb-doped Ge
single crystal is not measurable due to opacity, additional crystal growth experiments were
performed to verify the simulated flow velocity. Sodium nitrate (NaNO3) single crystals were
grown inside quartz glass tubes by both the AHP and AVC methods, with aluminum powder added
to the transparent melt to allow for visual capture of the flow pattern.
References:
[1]
E. Balikci, A. Deal, and R. Abbaschian, “Antimony-doped germanium single crystals grown from the
melt by the axial heat processing (AHP) technique,” J. Cryst. Growth, vol. 262, no. 1–4, pp. 581–593,
2004.
[2]
I. Avetissov, V. Kostikov, V. Meshkov, E. Sukhanova, M. Grishechkin, S. Belov, and A. Sadovskiy,
“Modeling of axial vibrational control technique for CdTe VGF crystal growth under controlled
cadmium partial pressure,” J. Cryst. Growth, vol. 385, pp. 88–94, 2014.
[3]
E. Balikci, A. Deal, R. Abbaschian, S. V. Bykova, V. D. Golyshev, M. a. Gonik, V. B. Tsvetovsky,
M. P. Marchenko, and I. V. Frjazinov, “A study on the morphological stability of faceted interfaces in
antimony-doped germanium single crystals grown by the axial heat processing method,” Cryst.
Growth Des., vol. 4, no. 2, pp. 377–381, 2004.
The study is supported by TÜBİTAK, TURKEY, grant no 212M030.
S02-P17
Microscopic modelling of confined crystal growth and dissolution
Høgberget, Jørgen*1, Røyne, Anja1, Dysthe, Dag Kristian 1, Jettestuen, Espen1,2
1
Department of Physics, University of Oslo, P. O. Box 1048 Blindern N-0316, Oslo (Norway)
International Research Institute of Stavanger, Forskningsparken AS, Gaustadalléen 21, 0349 Oslo (Norway)
2
We extend previous solid-fluid crystal growth and dissolution models [1] to include the effect
of confinement on solute systems. This is done by adding a plane surface subject to a constant
pressure at a certain equilibrium height above the crystal surface.
To model the repulsive interaction between the growing and the confining surface we use a
Debye-Hückel type potential. When the geometry of the growing surface changes, the value of the
repulsive interaction changes, and consequently also the value of the equilibrium height. This effect
is known as the “force of crystallization”. As we increase the applied pressure, we observe that the
growing surface is flattened, and the equilibrium concentration increases. This effect is known as
“pressure solution”.
With the addition of confinement to the model, the equilibrium concentration is no longer a
priori known. It is therefore an important step of the model to obtain equilibrium, such that a certain
level of supersaturation can be specified. We see from our results that the model reproduce
analytical equilibrium thermodynamics both with and without the effect of confinement.
We will present results where we have used the model to investigate the dependency of the
surface roughness with supersaturation for various levels of applied pressure, as well to
parameterize the linear growth rate constant. The latter is given as the slope of the curves presented
in Figure 1. These results all point in the direction that the model produce a temperature dependent
asymmetry between growth and dissolution.
Figure 1. Measurements of the linear growth rate (average height per time) as a function of the
supersaturation for a crystal growing in confinement under various applied pressures (indicated by
different lines). The supersaturation is calculated using the equilibrium concentration at the given
pressure.
References:
[1] Gilmer G. H. and Bennema P., Journal of Applied Physics, 43 (1972) 1347.
S02-P18
Dendritic Growth Kinetics in Undercooled Melts under Static Magnetic Fields
Gao, Jianrong*1, Kao, Andrew2, Pericleous, Koulis2, Galenko, Peter K.**3, Alexandrov, Dmitri V.4
1
Key Laboratory of Electromagnetic Processing of Materials (Ministry of Education), Northeastern University,
Shenyang 110819 (People’s Republic of China)
2
Centre of Numerical Modelling and Process Analysis, University of Greenwich, London SE10 9LS (United Kingdom)
3
Department of Physics and Astronomy, Friedrich Schiller University of Jena, Jena 07743 (Germany)
4
Department of Mathematical Physics, Ural Federal University, Ekaterinburng 620000 (Russian Federation)
*email: [email protected]; **email: [email protected]
Dendritic growth from undercooled melts has been intensively studied over the past seventy
years. Current attention is focused on the effect of fluid flow on dendritic growth, which has been
long assumed to be responsible for a discrepancy between theory and experiment in the low
undercooling region [1]. Recently, a new theory was proposed to describe dendritic growth kinetics
with melt convection at arbitrary Peclet numbers [2]. This new theory, termed Alexandrov-Galenko
theoy (AG theory for short), has a potential to account for a broad range of experimental data, but
has not been fully testified yet. This paper presents measured dendritic growth velocities in pure
nickel samples of different purity under static magnetic fields of intensities up to 6 T. The measured
growth velocities show strong dependences on the intensities of the static magnetic fields for
undercoolings below 100 K. This variation can be attributed to both the modification of residual
bulk flow and the introduction of thermoelectric magnetohydrodynamics (TEMHD). The measured
growth velocities were modeled using the AG theory by assuming magnetic field-tuned fluid flow
velocities. TEMHD in dendritic growth was modeled using an enthalpy-based method [3] to have
insights into the flow-dependent growth kinetics. The numerical simulation shows a good
agreement with the experimental observations and the analytical modeling. The effects of impurities
on TEMHD and dendritic growth kinetics are discussed.
Figure 1. Dendritic growth velocities of pure nickel (99.999% purity) as a function of undercooling. The solid circles
shows the measured data under a static magnetic field of B = 2 T. The solid line shows
the calculated data using the AG theory [2] assuming an incident flow velocity of U = 1.0 m/s.
References:
[1] Funke O., Phanikumar P., Galenko P. K., Chernova L., Reutzel S., Kolbe M., Herlach D.M., J. Cryst.
Growth 297 (2006) 211.
[2] Alexandrov D.V., Galenko P.K., Physics-Uspekhi, 57 (2014) 771.
[3] Kao A., Pericleous K., Magnetohydrodynamics, 48 (2012) 361.
S02-P19
Multiphase-field theories of crystallization: A comparative study
Gyula I. Tóth*1,2, Tamás Pusztai2,Bjørn Kvamme1, László Gránásy2,3
1
Department of Physics and Technology, University of Bergen, Allégaten 55, 5007 Bergen (Norway)
2
Wigner Research Centre for Physics, P.O.Box 49, 1525 Budapest (Hungary)
3
BCAST, Brunel University, UB8 3PH Uxbridge, Middlesex (United Kingdom)
We present a comparative study of the most widespread, free energy functional based multiphasefield theories, a technique used in modelling multicomponent and/or polycrystalline solidification.
Focusing on physical consistency, first we set up a list of both equilibrium and dynamic criteria, and
put several multiphase theories to this test. We show that even if planar two-phase interfaces are at
least numerical stationary solutions of the dynamic equations, they do not represent equilibrium, i.e.
they are not the solution of the general Euler-Lagrange equations in most of the existing multiphase
theories. In the rest, the planar interface = stationary solution compatibility is established either by
leaving the energy functional formalism for large number of phases or limiting ourselves to 3
phases. The latter also prescribes additional conditions for the form of the free energy functional,
and we are also not free in choosing equilibrium interfacial properties.
In order to resolve the problems of existing multiphase descriptions, we combine the successful
elements of the investigated approaches with a recently developed mobility matrix, together with
proposing a new free energy functional. The result is a new, general multiphase description for
arbitrary number of phases (or components), which (i) keeps the variational formalism, together
with (ii) showing natural reduction in the lack of a phase (or component) on the level of both the
free energy functional and the dynamic equations, (iii) using arbitrary (even anisotropic) pairwise
equilibrium interfacial properties, (iv) penalizing high-order multiple junctions, (v) showing
equilibrium stationary compatibility, (vi) avoiding the appearance of spurious phases on twophase interfaces, and (vi) showing numerical method independent results.
Our new model has been tested against (fluid-flow coupled) multi-component spinodal
decomposition as well as multi-dendritic solidification, thus demonstrating the robustness of the
theory.
Figure 1. Fluid-flow assisted spinodal decomposition in a ternary liquid.
References:
[1] G. I. Tóth, T. Pusztai, L. Gránásy, to be submitted.
[2] G. I. Tóth, B. Kvamme, to be submitted.
S02-P21
Thermoelectric Control of Crystal Growth
Kao Andrew1, Pericleous Koulis1
1
Centre of Numerical Modelling and Process Analysis, University of Greenwich, London SE10 9LS (United Kingdom)
It is known that an electric potential exists at the junction of two materials in the presence of a
thermal gradient. This, Seebeck effect, describes how the potential (ΔΨ) forms, when two materials
with varying Seebeck coefficients (S) are placed in thermal contact, and that at the boundary this
e.m.f varies with interface temperature. In a conducting melt, the current J is given by the
generalised form of Ohm’s law for moving media J   E  u  B  ST  , which includes the
Seebeck contribution. At the material interface the potential difference can then be written as
  ST . When this concept is applied to the evolution of a
growing dendrite [1], the interfacial temperature (Ti) can be
defined by the Gibbs-Thompson condition:
T i  Tm 
  ,   Tm
  mC0  Cli  , where
the second term
H
accounts for local free energy through surface energy anisotropy
 and curvature  and the final term accounts for solute
partitioning in binary alloys. This equation leads to a local
variation in surface temperature and the formation of
thermoelectric (TE) currents, which are therefore an inherent part
of solidification. When an external magnetic field is applied to this
situation, the TE currents interact with it to induce solutal
convection at the material interface, giving rise to the phenomenon
of TE magneto-hydrodynamics (TEMHD) first named by Shercliff
[2]. The resulting transport of mass alters the thermal and solutal
fields surrounding the dendrite, leading to changes in morphology.
These changes, which have been observed experimentally [3],
have been modelled by the authors using a 3D phase-field variant,
which allows the effects of convection [1]. This contribution
demonstrates how crystal morphology can be tailored, by varying
the strength and direction of the applied magnetic field as shown in
the figure 1(b), for a z-directed field Bz.
References:
[1] Kao A., Pericleous K., Magnetohydrodynamics, 48 (2012)
[2] Shercliff J A, “Thermoelectric Magnetohydrodynamics,” J. Fluid
Mech. 91, 231 (1979)
[3] Yasuda H et al. “Influence of the Static Magnetic Field on Dendritic /
Columnar Solidification, Observed by X-ray Imaging” Proc Light Metals
TMS 2015
(a)
(b)
Figure 1: (a) Normal
isothermal dendritic growth
of a binary alloy, and (b)
model-predicted disrupted
morphology when a strong
magnetic field acting along
the Z direction is applied.
(TN-normalised surface
temp-erature)
S02-P22
Orientation-field model for polycrystalline solidification in binary alloys with
a singular coupling between order and orientation
Bálint Korbuly1, Tamás Pusztai,1 László Gránásy1,2
1Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, P.O. Box 49, Budapest H-
1525, Hungary
2BCAST, Brunel University, Uxbridge, Middlesex, UB8 3PH, United Kingdom
In order to model polycrystalline solidification in binary alloys, we have adopted a new orientation field model
of Henry et al. [1] based on a singular coupling between the square gradient of the orientation field and the
phase field. Extending the orientation field to the liquid phase as in previous work [2] (where it is made to
fluctuate in time and space) and employing an economic model for foreign particles, we capture phenomena
like homogeneous nucleation of growth centres, and the formation of new grains at the growth front (growth
front nucleation), multi-dendritic solidification, dizzy dendrites, and polycrystalline seaweed structures. We also
investigate grain coarsening phenomena, and compared the model's predictions with existing models and
experiments.
Figure: A dendrit, a spherulite and a snapshot of grain coarsening
[1] H. Henry, J. Mellenthin, and M. Plapp: Orientation-field model for polycrystalline solidification with a
singular coupling between order and orientation. Physical Review B 86, art. no. 054117 (2012).
[2] L. Gránásy, L. Rátkai, A. Szállás, B. Korbuly, G.I. Tóth, L. Környei, and T. Pusztai: Phase-field modeling of
polycrystalline solidification: From needle crystals to spherulites – a review. Metall. Mater. Trans. A 45, (4)
1694-1719 (2014). Open access.
S02-P23
Rotationally-driven, axisymmetric oscillatory convection in a semitransparent
Czochralski melt model
1
Reza Faiez*, Yazdan Rezaei
Solid State Lasers Department, Laser & Optics Research School, Tehran P.O. Box 11365-8486, Iran
Thermal striations are commonly assumed to be caused by convective instabilities and
temperature fluctuations at the crystallization front. In the present hydrodynamic modeling of
Cz/Gd3Ga5O12 melt, time-dependent Navier-Stokes equations were solved for an axisymmetric fluid
flow in a cylindrical crucible with rc=60 mm, as the melt characteristic length, and hc=2rc as the
melt height. The crucible wall is at a constant temperature Tw=Tmp+ΔTmax , and it is assumed to be
an opaque and gray surface (ε=0.5) diffusely emitting and reflecting thermal radiation. The melt
absorbs and emits but not scatter radiation, and its optical properties (n=1.938 and a=0.1m-1) are
independent of temperature and wavelength. The melt free surface, with a meniscus configuration at
the crystal periphery, is a semitransparent diffuse-gray surface. The crystal (rx=24mm) is simulated
by a rotating plane surface (Tx=Tmp; ε=1) inclined toward the melt as a convex to melt interface.
Energy is transmitted through the melt surface to radiatively black ambient walls at constant
temperature, Ta=Tmp - ΔTmax . Depending on the crystal-rotation rate, Ω (rad/s) strictly periodic
flow was observed in the melt characterized by Pr=4.69, Gr=(1.142×103) ΔTmax and
Re=5.085×102Ω, and without Marangoni effect, Ma=(1.682×102) ΔTmax , where ΔTmax=108K is the
driving temperature differences.
Assuming that the rotationally-driven forces are approximately equal to the buoyancy forces at
Gr . Pr ≈ Re2, a significant change in the period of oscillating flow, tp(s) is expected at around
Ω~1.50. As shown in Fig.1, the convective flow remains steady for Ω<1.15 (tp=0). Increasing the
rotation rate, 1.15≤Ω≤1.50, the flow becomes an axisymmetric oscillatory one exhibiting a cold
plume descending from the crystal periphery along the rotation axis toward the crucible bottom.
Figure 1. Numerical results of the period of temperature oscillation and maximum stream
function with crystal rotation rate
Due to a relatively low Pr number, the melt flow is reheated before the cold plume descends
fully to the crucible bottom. The period of oscillations, tp found to be almost abruptly increased to
its maximum value of ~20s at Ω ~ 1.5 rad/s. From the tp(Ω) curves, the Marangoni effect has a
suppressing effect on the oscillatory flow for the range of 1.2<Ω<4.0, so that the tp,max decreased
from ~20s to ~11s in the presence of thermocapillary forces. Striation distances, ds can be estimated
by ds= vztp where vz is the crystal pulling rate, and the frequency of oscillations in the vicinity of the
crystallization front is given by ω=(1/tp)(δT2/α) where δT is the thermal boundary layer thickness
and α is the thermal diffusivity of the melt. Hence, tp,max corresponds with the lowest frequency of
thermal fluctuations and largest striation distances, which affect the crystal homogeneity much
more than do the high-frequency ones.
S02-P24
Thermal stability and spontaneous breakdown
of free-standing metal nanowires
Bogdan Ranguelov1, Paraskevas Giazitzidis2, Panos Argyrakis2, Michail Michailov*1
1
Institute of Physical Chemistry, Bulgarian Academy of Sciences, 1113 Sofia (Bulgaria)
2
Aristotle University of Thessaloniki, Thessaloniki (Greece)
Recently we have suggested a new physical model for spontaneous, hole-mediated
breakdown of metal monatomic nanowire located on crystal surface (M. Michailov, D. Kashchiev,
Physica E 70 (2015) p. 21–27). The physical scenario of breakdown process implies three
consecutive steps of nanowire rupture including (i) formation of active atoms, (ii) generation of
single atomic vacancy and (iii) evolution of single vacancy into an unrecoverable vacancy cluster
(hole). In all these steps preceding and finally causing the nanowire rupture, the impact of the
substrate is significant. The substrate could act on nanowire stability in two directions. It can
stabilize or in contrast it can facilitate the nanowire rupture depending on different factors as the
anisotropy and softness of the surface potential, lattice misfit between substrate and nanowire
atomic arrangement, etc. These competing processes are operated by the substrate/nanowire
interface energy minimization. Since a large number of experiments deal with nanowire features on
a substrate, the evaluation of substrate contribution on nanowire stability is essential. Therefore, the
knowledge of thermodynamic behavior of a free-standing or nanowires not affected by any external
forces is important. Does the vacancy and hole formation model is valid solely for epitaxial
interfaces? In the present study, grounded on continuous space Monte Carlo atomistic simulations,
we discuss this problem analyzing the thermal behavior of free metal monatomic chain for which
the influence of the substrate is entirely avoided. The extensive atomistic simulations demonstrate
that free-standing nanowire follows more elementary mechanism of rupture. The formation of a
single atomic vacancy causes non-recoverable nanowire breakdown. Hence, because of the missing
stabilization role of the interface the rupture kinetics is much faster. Describing this kinetics via rate
equations, we evaluate some important time- and temperature-dependent physical features of the
free-standing nanowire as mean lifetime τ, number of vacancies Nv(t), and the probability Pv(t), for
generation of at least one vacancy until time t, Figure 1. Hence, providing insight into the
mechanism and kinetics of spontaneous thermal rupture of a free monatomic metal nanowire, the
present study reveals the degree of validity of the hole-mediated nanowire breakdown mechanism.
Figure 1. Temporal evolution of Cu free-standing nanowire at 10 K at 0 (upper atomic chain), 600,
1100, 1600 Monte Carlo Steps
S02-P25
Towards the understanding of hydrozincite precipitation; Population balances
on sparingly soluble compounds.
Martín-Soladana Pablo M. 1, Lai Xiaojun 1, York David 1, Buchkremer Anne 2, Granito Nathalia 2,Wise
Geoff 2. Xu Dan 2,Martín-de-Juan2Luis.
1
Institute of Particle Science and Engineering, School of Chemical and Process Engineering. University of Leeds, LS2
9JT, UK.
2
Procter & Gamble Co. Newcastle innovation centre. Newcastle. United Kingdom
The control of particle size in reactive crystallization is of interest, among others, to
pharmaceutical, catalyst and cosmetic industries. In this work, the contributions of nucleation
growth and aggregation to the final particle size distribution (PSD) were resolved for the case of
hydrozincite, a sparingly soluble compound important for its high surface area and for being a
precursor of zinc oxide. Population balance models (PBM) and momentum theory, as proposed by
Jones et al.[1] , were, used to study the influence of the associated process parameters, such as pH,
shear rate and concentration over the final PSD. The kinetic parameters (nucleation rates, growth
rates and aggregation kernels) were obtained by optimizing the model to the experimental PSD
data.
The particle size distribution was obtained by static light scattering and FBRM. The particles
were further characterized by measuring the Zeta potential, X-ray diffraction and microscopy
techniques. STEM and XRD show primary particles from 8 to 25 nm arranged in compact
aggregates with fractal dimensions from 1.7 to 2.7 and sizes of 7-50 µm as light scattering and
SAXS measurements shows. More dispersed aggregates were found at lower pH. This was
attributed to the higher surface charge shown by zeta potential measurements. The results of this
study are of potential used in the design of crystallizers and to improve the knowledge on
population balance.
Reference:
[1] Jones, A. G., Hostomský, J., & Wach, S. (1996).. Chemical Engineering Communications,
146(1), 105–130. S02-P26
Effects of boundary conditions and geometry on structural and thermodynamic
properties of modeled semiconductors
Natalia Podolska*1,2
1
Saint-Petersburg Branch of Joint Supercomputer Centre, 26 Politehnicheskaia str., Saint-Petersburg (Russia)
2
Ioffe Institute, 26 Politehnicheskaia str., Saint-Petersburg (Russia)
Understanding of behaviour and properties of semiconductor materials at different scales (bulk,
films, nanostructures etc.) is a key question for developing of semiconductor technologies and
modelling of crystal growth and structures (heterstructures, quantum dots etc.) [1,2,3].
In the paper, we present the numerical analysis of effects of boundary conditions and geometry
(size, shape etc) on structural and thermodynamic properties of wurtzite and zinc blende II-VI and
III-V ternary compounds. To find the structural and thermodynamic properties, the simulations have
been carried out with a modified valence force field method and models, based on some ideas
described in [4]. The use of multiple computation runs was used to improve the representative
statistics of the valence force field computations, which is necessary for an accurate prediction of
properties and their composition dependences [4].
Interatomic distances (anion-cation, anion-anion and cation-cation) and thermodynamic
properties (mixing energy, interaction parameter, enthalpy of mixing etc) will be presented as
functions of sizes, scales (from bulk to thick and thin films, wires or columns) and shapes (films
with different thickness, cubes, columns with parallelogram and diamond-shaped cross-sections).
Good agreement with the experimental data was demonstrated. Moreover, the simulation results
were compared with results obtained by other methods.
The reported study was partly supported by RFBR (Russian Foundation for Basic Research),
research project for young researchers No.14-08-31581.
Periodic BC
In-As
Counts
Free
Na=512
Free
Na=2744
4
Mixing Energy Em (kJ/mol)
Ga-As
10
Number of atoms
100
1k
10k
3
2
0.38
kJ/mol
1.55 kJ/mol
1
Periodic BC
Free BC
Em@Na=110592
0
2.40 2.45 2.50 2.55 2.60 2.65 2.70
Anion-Cation Distance (A)
100k
In0.5Ga0.5As
-17
10
-16
10
2
Surface Area (m )
-15
10
Figure 1. Ga-As and In-As distances (left) in zinc blende In0.5Ga05As as well as mixing energy as a function of surface
area (right). Shape of modeled crystals is cube. "Free" denotes that "free surface" and "Periodic" denotes that periodic
(bulk crystal) boundary conditions were used. "Na" is the number of atoms in the modeled crystals. Vertical arrows (right)
denote differences between values of the mixing energy.
References:
[1] Joyce H.J., Gao Q., Tan H.H., Jagadish C., Kim Y. et al., Progress in Quantum Electronics 35 (2011) 23
[2] Porte L., Journal of Crystal Growth 273 (2004) 136–148
[3] Guisbiers G., Nanoscale Res Lett (2010) 5 1132–1136
[4] Karpov S., Podolskaya N., Zhmakin I., and Zhmakin A., Phys.Rev.B 70 (2004) 235203
S02-P27
The Conductivity Of Two-Dimensional Electron Crystal On The Surface of
liquid 4He. Modeling.
Syvokon Vitalii 1, Nasyedkin Kostyantyn 2, Sharapova Iryna*1
1
B.Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine,
47 Lenin Ave., Kharkov 61103 (Ukraine)
2
RIKENCEMS, Hirosawa 2-1, Wako 351-0198, (Japan)
The surface electrons over liquid helium (Wigner crystal) is a spatially ordered state of a twodimensional system of classical particles with the Coulomb interaction. Ordering occurs when the
ratio between the potential and kinetic energies (plasma parameter Г) of the particles exceeds a
certain value (Г > 130). The order-disorder transition in this system is a Berezinski-KosterlitzThouless-type phase transition. The phase transition can be observed while investigating the
transport characteristics of the electron layer (complex conductivity) which are different in the
ordered and disordered states.
When the crystal is exposed to an external electric field directed along the surface of the liquid
(guiding field), the layer conductivity varies nonmonotonically with the increasing field. In the limit
of high guiding fields both the components of the crystal conductivity are close to the conductivity
of a disordered electron layer.
It is found [1] that the conductivity of a Wigner crystal changes drastically as the holding
potential decreases. The active part of the conductivity was observed to change sharply in a narrow
interval of compressing voltages, which suggests a possible transition in the system. The reactive
part of the conductivity was varying smoothly. The process observed could hardly be related either
to melting, because it occurred much below the melting temperature, or to a dynamic transition,
because the measurement was made in low guiding fields. The sharp changes in the conductivity
may be accounted for by the disturbance of the crystalline order when the holding field decreases
and a solid disordered phase is formed. “Evaporation” of the electrons onto the higher-lying surface
levels was assumed as a possible mechanism in [2].
This study is a continuation of the investigation of the electron crystal conductivity under the
condition of a decreasing holding potential. The model calculation suggests another possible reason
for the observed behavior of the conductivity.
The modeling was reduced to calculating a possible configuration of the electron after their
redistribution provoked by the compressing field. A correlation density function was calculated to
characterize the degree of ordering of the electrons.
The modeling results show that a decrease in the holding field causes redistribution of the
electrons. As a result, their surface density increases in the direction from the center of the layer
towards its edge though a certain order of the electron arrangement still persists. Besides, it is found
that the active part of the conductivity increases sharply even with a slight decrease in the holding
potential, i.e. the resistance of the layer increases.
References:
[1] Nasyedkin K. A., Syvokon V. E., Neoneta A.S., Pisma v ZhETF, 91 (2010) 652.
[2] Slavin V. V., Krivchikov A. A., Fiz. Nizk. Temp., 38 (2012) 1390.
S02-P28
Transitions between regimes of crystal growth kinetics under decaying
supersaturation
Vesselin Tonchev*1,Christo Nanev1, Georgi As. Georgiev2, Peter Vekilov3
1
Institute of Physical Chemistry, Bulgarian Academy of Sciences, 11 Acad. Georgi Bonchev str., Sofia (Bulgaria)
2
Faculty of Biology, University of Sofia “St. Kliment Ohridski”, 8 Dragan Tsankov blvd.. Sofia (Bulgaria)
3
Department of Chemical Engineering, University of Houston, Houston, TX 77204-4004(USA)
Numerous industrial and laboratory processes involve the precipitation of crystals during which
solute is not supplied, thus supersaturation decays in time. This may induce a transition between
different regimes of crystal growth that needs to be accounted in crystallization models of particle
size and distribution. In order to model the transition between regimes of crystal growth we assume
that the normal growth velocity is rg   g S g where g is a kinetic coefficient and S is the
supersaturation. The growth rate is defined as twice the normal velocity (in units of the g=1 normal

r
velocity) Gg  2 g  2 Bg  g , S/S0 is the normalized supersaturation and Bg  g S0g 1 . The
1
1S0
different kinetic regimes are characterized by their respective values of the kinetic exponent g.
Following the “morphology selection principle” [1] we assume that if two growth regimes with
kinetic exponents g1 and g2 are simultaneously available in the system, the growth starts with the
faster one. We show that in this case, if the growth starts from the regime with g1, transition into a
regime with g2 is possible only if g1>g2, fig. 1a. Thus, in order to have transition into a regime with
higher value of g this should become available at some value of the decreasing supersaturation; this
transition is illustrated with experimental data on the crystallization of Ni in fig.1b.
These findings will contribute to the refinement of models of batch crystallization aimed at
predicting the properties of the crystal population and the kinetics of crystal synthesis.
a
b
Figure 1. Two possible transitions along the decaying (normalized)supersaturation: (a) both regimes
with g1=2 and g2=1 are available from the beginning of the growth; (b) growth starts with g1=1
and then in certain point of supersaturation another regime with g2 = 2 appears
References:
[1] Ben-Jacob E., Contemporary Physics, 34 (1993) 247.
[2] Dimitrov V., J. Crystal Growth, 76 (2003) 504.
S02-P29
EFFECT OF SURFACE RECONSTRUCTION ON Ge‐Si(001) HETEROEPITAXY Paramita Ghosh Indian Institute of Technology Kanpur, Kanpur‐208016, India The most widely studied heteroepitaxial system is Ge on Si(100), due to its ease for integration with Si-based
devices. The (100) surface of Silicon shows several reconstructions, of which the 2 × 1 is the most relevant for
growth at high temperature in Molecular Beam Epitaxy (MBE). Surface reconstruction changes the nature of
bonding on the surface inducing additional anisotropies in surface energy and affects properties of the growing
film.
We have developed a two component three dimensional solid-on-solid model on simple cubic lattice, with
necessary modifications to account for surface reconstructions. Additionally, the elastic effects due to lattice
mismatch between the film and the substrate are modeled using a harmonic ball and spring model of elasticity.
This model ables to explain most of the features of Si on Si(001) homoepitaxy like dimer chain formation,
island size and shape distribution and their dependence on temperature[1]. In the case of Ge on Si(001), this
model is able to reproduce strain induced effects like dimer chain vacancy formation and alignment of
vacancies around 1ML coverage[2]. In this study we have revealed how elastic effects, coupled with
reconstruction can explain the observed behavior at the early stages of growth of Ge on Si(001).
We have extended the simulations to multilayer growth to study how reconstruction plays a role in the 2D/3D
growth transition. Our goal here is to see if it can be used to accurately predict formation and shapes of
quantum dots which are formed during Stranski-Krastanov growth.
References
[1] P.Ghosh, M. Ranganathan, Surf. Sci. 630 (2014) 174.
[2] P. Ghosh, P. Nath and M. Ranganathan, Surf. Sci. 639 (2015) 96.
S02-P30
Interatomic distances and thermodynamic properties of wurtzite
and zinc blende AlInGaN
1
2
Materials based on quaternary III-V semiconductor alloys, such as AlInGaN, are very inportant
for developing of modern micro- and optoelectronics. At the same time, there is a lack of
experimental data and theoretical information on structural (interatomic distances) and
thermodynamic properties of these quaternaries. So, numerical simulations seem as the most
informative and direct way of obtaining this information.
In the paper, we present simulation results and analysis of the structural (anion-anion, cationcation, anion-cation) and thermodynamic properties (mixing energy and thermodynamic functions)
of bulk wurtzite and zinc blende AlxInyGa1-x-yN as a function of compositions 'x' and 'y'. To find the
structural (anion-cation, cation-cation and anion-anion) and thermodynamic (mixing energy,
enthalpy and entropy of mixing, spinodal decomposition) properties dependence on a function of
compositions, the simulations have been carried out with the modified valence force field method
and some ideas described in [1], adapted for quaternary alloys. The multiple computation runs was
used to improve the representative statistics of the valence force field computations, which is
necessary for an accurate prediction of properties and their composition dependences [1]. Analytical
approximation of mixing energy as a function of compositions 'x' and 'y' in AlxInyGa1-x-yN will be
presented. Using the approximation, thermodynamic properties of the solid solution such as
enthalpy and entropy of mixing, spinodal decomposition will be described.
Good agreement with the experimental data was demonstrated.
Figure 1. Mixing energy in kJ/mol of wurtzite AlxInyGa1-x-yN as a function of compositions 'x' and 'y'.
References:
[1] Karpov S., Podolskaya N., Zhmakin I., and Zhmakin A., Phys.Rev.B 70 (2004) 235203
[2] Monroy E., Gogneau N., Enjalbert F., Fossard F., Jalabert D., Bellet-Amalric E., Le Si Dang, Daudin B.,
J. Appl. Phys. 94 (2003) 3121
S02-P31
A numerical model on nano-line patterning of c-plane sapphire substrates for
selective area growth of AlN islands
I. Davis Jacob, A. Rosy, G.K.Priya Merline, K. Prabakaran, K. Baskar and M. Chitra*
Crystal Growth Centre, Anna University, Chennai (India)
*email for correspondence : [email protected], [email protected]
Abstract: A simple numerical model of nanopatterning of c-plane sapphire substrates for
selective area growth of AlN islands is proposed. This is to reduce the threading dislocations on the
GaN epitaxial layers arising due to lattice mismatch between GaN and sapphire. Lattice constant of
sapphire is greater than that of GaN whereas the lattice constant of aluminium nitride is less than
that of GaN. When the two lattices of sapphire and AlN are alternated periodically on the surface of
the c-plane substrate, the lattice mismatch between the GaN and alternating sapphire/AlN substrate
is reduced laterally on the c-plane interface. This will have a tremendous impact on the quality of
the GaN epitaxial layers formed on the substrate. The dislocation density on the GaN epitaxial
layers is expected to decrease due to better lattice matching conditions. A simple numerical model
is proposed based on the origin of line dislocations in a given direction (One Dimension) and in a
given area (Two Dimensions). It is found that a minimum of one line dislocation would arise
laterally on the (c-plane) interface of GaN-sapphire beyond an atomic distance of five lattices of
sapphire whereas a line dislocation on the (c-plane) interface of GaN-aluminium nitride would arise
beyond 40 lattices of aluminium nitride in a given direction. The theoretical ratio of sapphire and
AlN lattices in a given direction and that in a given area are estimated for minimum dislocation
conditions. Sapphire can be patterned or etched periodically in the shape of wells (line-patterning)
on the c-plane surface for selective area growth of AlN. The periodicity, line-patterning density and
sizes (width of wells) of the aluminium nitride islands were estimated.
S02-P32
Modeling of axial heterostructure formation in multicomponent III-V nanowires
Koriakin Aleksandr*1,2, Sibirev Nikolai1,2, Dagou Zeze2,3, Dubrovskii Vladimir1,2
1
St. Petersburg Academic University, Khlopina 8/3, St.Petersburg (Russia)
2
ITMO University, Kronverkskiy pr. 49, St. Petersburg (Russia)
3
School of Engineering and Computing Sciences, South Road, Durham (UK)
Heterostructure nanowires (NWs) have a wide range of potential applications in opto- and
nanoelectronics where the presence of an abrupt heterojunction is highly desirable for designing
devices with high-performance characteristics. Vapor-liquid-solid (VLS) growth is probably the
method most used to synthesize NWs because it facilitates the formation of relatively sharp
interfaces for several III-V semiconductors, elements from group V may be easily interchanged
(e.g. InAsP/InAs, GaAsP/GaP [1]). In turn, the formation of abrupt interfaces is much more difficult
when elements from group III are interchanged (e.g. for AlAs/GaAs, GaInAs/InAs,
InGaAs/GaAs[1]). This difference of interface sharpness has been explained by the fact that
solubility of group III atoms in the catalyst droplet (10-40%) is usually higher than that of group V
atoms, e.g. arsenic and phosphor (1-6%). Despite the variety of experimental data, theoretical
studies of heterojunction formation in NWs are very limited. Moreover, only a small set of
materials can be considered within the assumptions made.
In this paper, we propose a model describing heterostructure formation in ternary III-V NWs
grown by catalytic VLS method. Our approach is based on the determination of chemical potentials
of dissolved materials using the regular solution model and the Stringfellow formula for the
computation of the interaction coefficients of species present in the droplet [2]. The model allows
the estimation of the heterojunction width dependence on the growth temperature. This dependence
has not been reported before by any previous theoretical studies. The AlGaAs/GaAs heterojunction
formation in the Au-catalyzed AlGaAs NWs was considered as an example of ternary system. The
heterojunction width was found to increase with the growth temperature with a second-order
polynomial dependence (Figure 1).
Figure 1. AlGaAs/GaAs heterojunction width as a function of the growth temperature.
References:
[1] Messing M. et al., Nano Lett., 11 (2011) 3899
[2] Glas F., Appl. Phys., 108 (2010) 73506
SESSION 3
Product and Process Design of Pharmaceuticals and Fine Chemicals
Using crystal growth to generate single chirality from an achiral start
Rene Steendam1, Jorge Verkade1, Tim van Benthem1, Hugo Meekes1, Willem van Enckevort1, Jan Raap2,
Floris Rutjes1, Elias Vlieg1
1
Radboud University, Institute for Molecules and Materials, Nijmegen, The Netherlands
2
Leiden Institute of Chemistry, Leiden University, The Netherlands
In recent years the process of Viedma ripening, in which a racemic mixture of enantiopure
crystals is ground, has been found to be an effective and elegant way to deracemize a chiral
compound [1]. Here we show that a combination of an organic reaction with Viedma ripening leads
to the remarkable result that from fully achiral starting conditions, an end state of single chirality
can be reached in a single process [2]. This approach not only provides more insight into the origin
of homochirality in life but also offers a pathway to acquire enantiopure compounds for industrial
applications.
Figure 1. A schematic showing that a chemical reaction of achiral starting material first leads to a mixture of left and
right-handed crystals (red and blue), that subsequently transform to single chirality.
References:
[1] W.L. Noorduin et al., Angew. Chem. Int. Ed. 48 (2009) 9600.
[2] R.R.E. Steendam et al., Nature Commun. 5 (2014) 5543.
Crystallisation Characteristics of an Organic Material in Industrial Mother
Liquor with Impurities
Khan Shahid 1, Mahmud Tariq*1, Roberts Kevin 1, Zhu Xiaofeng 1, George Neil2 and Sillers
Pauline2
1
Institute of Particle Science and Engineering, School of Chemical and Process Engineering, The University of Leeds,
Leeds LS2 9JT, UK
2
Syngenta, Jealott's Hill International Research Centre, Bracknell, Berkshire RG42 6EY, UK
In pharmaceutical and fine chemical industries, the isolation and purification of organic
materials are commonly carried out using various solution crystallisation techniques including the
batch cooling crystallisation process. In industrial crystallisation processes, mother liquors usually
contain unwanted dissolved molecules (generally referred to as impurities) produced via reaction
steps prior to the crystallisation and their concentration may vary from batch to batch. It has long
been established that the supersaturation driven nucleation and crystal growth rates can change
profoundly even in the presence of low levels of impurities added intentionally to or inherently
present in the solution, and thus affects the size, shape and purity of the product crystals. This could
also impede efficient downstream processing of crystals such as filtration, drying and milling. In
order to control industrial crystallisation processes to meet product specifications, such as narrow
crystal size distribution, high chemical purity and desired crystal morphology, with high product
yields, it is important to develop a detailed understanding of the crystallisation characteristics of
product materials in the mother liquors containing process generated impurities. This can be
achieved via replicating the industrial process at laboratory scales in the presence of impurities.
The work reported here investigated the crystallisation behaviour of an organic material
(referred to as compound A due to confidentiality) from an industrial mother liquor (which mainly
contains an organic compound), corresponding pure solvent and the pure solvent doped with the
process generated impurity as a function of representative processing variables, e.g., level of
impurities, seeding and cooling profile. Experiments were carried out in a 500 mL jacketed glass
stirred tank crystalliser with temperature controlled using Julabo FP50-HD thermostatic bath. The
metastable zone width and induction time for the nucleation of compound A were determined using
a turbidimetric method as a function of both cooling rate and solute concentration in the pure and in
impurity added solvent. ATR-FTIR spectroscopy coupled with a PLS calibration model was used
for on-line monitoring and control of supersaturation during the batch cooling crystallisation of
compound A.
The metastable zone width was found to be wider in the mother liquor and in the solvent doped
with impurity compared with that in pure solvent. The induction time for nucleation of compound A
increases with increasing impurity concentration. A significant outcome of this research is reflected
in the observations that the crystals produced in pure solvent have a much different physical form
compared to those crystallised from mother liquor. The former crystals tend to be smaller and
heavily agglomerated when compared to the latter which display superior crystal quality and
external morphology. The latter perhaps is a reflection of the nucleation and solubilisation abilities
of the other components present in the mother liquor. However, in the pure system, particles
spontaneously nucleated at much higher supersaturation levels leading perhaps to an excessive
primary nucleation rate resulting in smaller and more agglomerated crystals.
Preferential Orientation of β-phase Triacylglycerol on Graphite Surface
Fumitoshi Kaneko1*, Shinichi Yoshikawa2, Haruyasu Kida2, Kiyotaka Sato3
1
Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka (Japan)
2
R&D Division for Future Creation, Fuji Oil Co., Ltd., Tsukubamirai, (Japan)
3
Hiroshima Univeristy, 1-4-4, Higashihiroshima (Japan)
In order to promote the lipid crystallization, surfactants and materials having long hydrocarbon
chains have been used as additives. It is considered that their alkyl chains act as templates for the
heterogeneous nucleation by ordering the hydrocarbon-chain moieties of lipids. Recently, it has
been clarified that inorganic and organic crystals (i.e., talc, graphite, carbon nanotube, theobromine,
terephthalic acid, and ellagic acid dihydrate) remarkably promoted the lipid crystallization to form
thermodynamically stable crystals [1, 2]. These additives are sparingly soluble in lipids and possess
no long hydrocarbon chains in their molecules; therefore, we assume that the promotional effects
are caused by the strong intermolecular interactions between the surfaces of the crystalline materials
and lipids. To understand the mechanism of this type of heterogeneous nucleation, we launched an
investigation of the molecular orientation in trilaurin (LLL) crystals generated on the flat hexagonal
net plane of a graphite sheet.
In this study, the orientation of the LLL β-form crystals generated on the surface of a graphite
sheet was examined by X-ray diffractometry (XRD) and polarized Fourier transform infrared–
attenuated total reflection (FTIR–ATR) spectroscopy. Figure 1 shows the XRD profile taken under
the condition that the scattering vector is parallel to the normal of the graphite sheet. There appear
the intense 00l reflections due to the long spacings of LLL β-form crystals, whereas the reflections
due to the subcell structure (T//) in the 2θ region of 19-24° are significantly week, suggesting that
the lamellar planes of the LLL crystals were parallel to the surface of the graphite sheet. Figure 2
shows the polarized FTIR-ATR spectra, where the p- and s-polarized spectra emphasize the
components of transition moment normal and parallel to the sample surface, respectively. The ppolarized spectrum shows CH2 wagging progression bands much more intense than those in the spolarized spectrum. Since the transition moments of the wagging modes are parallel to the long
hydrocarbon chains, the ATR spectral feature is consistent with the model obtained by XRD
experiments. These results indicate that the heterogeneous nucleation of the LLL β-form crystals
takes place with the lamellar orientation parallel to the surface of the graphite sheet.
Figure 2. Polarized FTIR–ATR spectra of LLL β
Figure 1. XRD profile of LLL β
References:
[1] Shinichi Yoshikawa, Haruyasu Kida, Kiyotaka Sato, J. Oleo Sci., 63 (2014) 333-345
[2] Shinichi Yoshikawa, Haruyasu Kida, Kiyotaka Sato, Eur. J. Lipid Sci. Technol., 117 (2015) in press.
Crystallization of L-Glutamic acid polymorphs in stirred and stagnant
conditions
Tahri Yousra*1,2, Gagnière Emilie1, Chabanon Elodie 1, Bounahmidi Tijani2, Mangin Denis1
1
Université de Lyon, Université Claude Bernard Lyon 1, CNRS, UMR 5007, LAGEP, 43 Boulevard du 11/11/ 1918,
69622 Villeurbanne (France)
2
Ecole Mohammadia d’Ingénieur LASPI, Avenue Ibnsina, 10765 RABAT (Morocco)
This work deals with the study of the polymorphism of L-Glutamic acid (LGlu) which can
crystallize in two known monotropic polymorphs: the stable form β with needle like shape and the
metastable form α with prismatic shape [1]. Since the β form can generate many difficulties in
production, transport and storage [2] it is more suitable to produce α form. Two experimental
devices were used. Cooling crystallizations in water were performed in both a stirred double
jacketed vessel of 2 L and a non-agitated thermostated cell of 4 mL. The crystallization was
monitored in situ by a video probe in stirred conditions and by a microscope in stagnant conditions.
Effect of temperature and supersaturation on the polymorphism of LGlu was investigated.
In stirred conditions, at low supersaturation, the effect of temperature was relevant: at high
temperatures only the stable form β nucleated while almost only the metastable form α was
observed at low temperatures. At high supersaturation, both polymorphs crystallized with high
percentage of α at low temperatures (around 10°C) and high percentage of β at higher temperature
(around 45 °C).These results suggest that LGlu polymorphism is strongly affected by temperature
and does not obey to the Ostwald rule of stages. It was also observed the β polymorph habit
changed with supersaturation. At low supersaturation, the β form exhibited needle-shaped habit
which is the shape generally reported [1]. However at high supersaturation, β crystals showed
surprising lozenge slab habit close to that of α form (figure 1 a). These lozenge slabs were
confirmed to be the β polymorph by X-ray Diffraction. Therefore, relying only on the appearance to
differentiate between the two LGlu polymorphs can be misleading.
In stagnant conditions, spontaneous nucleation of LGlu could not be observed at similar low
supersaturation as in the stirred vessel within 72 hours. At high supersaturation only the polymorph
β nucleated as lozenge slabs (Figure 1b) and grew with the same shape or transformed to hexagonal
slabs depending on the supersaturation.
These results will be used to model the competition between nucleation and growth of the two
polymorphic phases.
Figure 1. (a) Images of LGlu polymorphs in stirred conditions: (1) α form,(2) β form with lozenge shape (3) β form with
needle shape. (b) Microscope image of β polymorph with lozenge shape in stagnant conditions
References:
[1] Kitamura, M. (1989). Polymorphism in the crystallization of L-glutamic acid. Journal of crystal growth,
96(3), 541-546.
[2] Bernstein, J. (2007). Polymorphism in molecular crystals (Vol. 14). Oxford University Press, chapter1.
Design of Optimal Start-up Procedures for MSMPR Crystallizers
Kamaraju Vamsi Krishna*1, Power Graham1, Hou Guangyang2, Zhao Yan1, Glennon Brian1
1
Synthesis and Solid State Pharmaceutical Centre (SSPC), Department of Chemical and Bioprocess Engineering,
University College Dublin, Belfield, Dublin 4, Ireland
2
APC Ltd, Belfield Innovation Park, Dublin 4, Ireland
With increasing interest on continuous processing in pharmaceutical manufacturing due to its
distinct advantages over batch operation in terms of delivering consistent product, safety, and
increased productivity, Mixed Suspension Mixed Product Removal (MSMPR) crystallizers are
widely employed for continuous crystallization of active pharmaceutical ingredients (APIs).
However, design of optimal start-up procedures for MSMPR is not sufficiently addressed in the
literature yet, which can critically affect the economic operation of continuous crystallization
processes.[1] Few attempts have been made in the past to understand the effect of various process
conditions on the settling time to reach steady state. Hou et al. (2014) experimentally studied the
impact of various seed distributions and concluded that seeding with previously isolated MSMPR
product suspension shows the shortest settling time.[2] Su et al (2015) developed rigorous
mathematical models to demonstrate the application of concentration control strategy for start-up
procedure of single stage and cascaded MSMPR antisolvent crystallizers.[3] Further, Yang and
Nagy (2015) have recently studied the start-up optimization methods for combined cooling and
antisolvent MSMPR crystallizer by choosing optimal trajectories to achieve minimum start-up
duration and amount of waste.[4] The current study presents a systematic methodology for
designing optimal start-up procedure using the advantages of batch crystallization.
The effect of different initial suspension properties on the settling time for steady state is
studied with the help of dynamic simulations based on population balance modeling of MSMPR
crystallizers. Thus, batch control strategies were employed to achieve the target suspension
properties required to minimize the amount of out-of-spec MSMPR product. Experimental
validation confirms the advantage of the proposed methodology compared to general start-up.
(a)
(b)
Figure 1. Dynamic simulations of MSMPR with different initial suspensions –
(a) Concentration profiles; (b) Profiles of volume-weighted mean size of product crystals
References
1.
2.
3.
4.
Myerson, A.S., et al., Journal of Pharmaceutical Sciences, 2015. 104(3): p. 832-839.
Hou, G.Y., et al., Crystal Growth & Design, 2014. 14(4): p. 1782-1793.
Su, Q., Z.K. Nagy, and C.D. Rielly, Chemical Engineering and Processing: Process Intensification, 2015.
89(0): p. 41-53.
Yang, Y. and Z.K. Nagy, Industrial & Engineering Chemistry Research, 2015.
A phenytoin polymorph accessible via surface mediation
Daniela Reischl,1 Christian Röthel,1,2 Eva Roblegg,1 Heike M.A. Ehmann3 and Oliver Werzer1*
1
University of Graz, Institute Pharmaceutical Sciences, Department for Pharmaceutical Technology, 8010 Graz,
Austria
2
Graz University of Technology, Institute for Solid State Physics, 8010 Graz, Austria
3
Graz University of Technology, Institute for Chemistry and Technology of Materials, 8010 Graz, Austria
The exploration for new polymorphic forms of organic compounds is one of the most effective
route for controlled manipulation of drug release from solid dosage forms. In recent years extensive
and theoretical work was applied to identify and predict new polymorphs, especially those useful
for pharmaceutical applications. In general, changes in parameters like choice of solvent,
concentration, temperature and pressure are capable of changing the polymorphic assembling as
another local energetic minimum is accessible. Another route for a polymorphic alteration is
crystallization in close vicinity of surfaces. Such crystallization often reveals the formation of new
polymorphs which are only existent some monolayers off a solid surface and are therefore classified
as surface induced or surface mediated.[1][2] Furthermore, there is evidence that some of these
surface mediated phases result from growth kinetics rather than certain thermodynamic
parameters.[2]
In this work, we demonstrate the formation of a new surface mediated polymorph of phenytoin,
a drug molecule, in a model experiments. So far, experiments were only able to resolve one
polymorph of phenytoin either on in the bulk or on surfaces.[3][4] Anyway, by the usage of simple,
but very effective techniques like controlled drop casting, spin coating or vacuum deposition the
formation of a new surface mediated polymorph is demonstrated at conventional silica surfaces. As
will be shown, this phase is only accessible in thin films thus sophisticated experimental techniques
like atomic force microscope as well as gracing incidence x-ray diffraction are required to gain
information on this new polymorph within thin films. The results reveal a morphology which is
distinct from those of the bulk phase.[3][4] Furthermore the unit cell of the surface mediated phase
is extended compared to this of the bulk phase meaning a less dense packing is present in the
surface mediated phase. This typically means that the stability of the surface mediated phase is also
reduced, which is further supported by in-situ temperature dependent measurements; a monotropic
solid-solid phase transition into the bulk phase takes place at around 160°C. As an application
relevant consequence, this surface phase has a significantly better dissolution behavior compared to
phenytoin in its bulk polymorph with the release into the dissolution media being much faster. The
results presented show a very promising approach for drug dissolution enhancement which might be
directly accessible within application like transdermal patches or buccal stripes. For an application
in conventional solid oral dosage forms, some additional work is required to generate this
polymorph onto nanoparticles or materials suitable for powder processing which should be
accessible with the pre-knowledge from this study. .
References:
[1] D. Nabok, et. al. Physical Review B 12 (2007) 235322.
[2] B. Wedl, et. al. RSC Advances 01 (2012) 4404
[3] H. M.A. Ehmann, et. al. J Phys Chem C 118 (2014) 12855
[4] H. M.A. Ehmann, et. al. Cryst. Growth Des. 15 (2015) 326
Nucleation Kinects of Co-crystal by Simultaneous Monitoring of Dissolution and
Crystallisation using Process Raman Technique: Precipitation of Burkeite
Boyang. Zou1*, Xiaojun Lai1, Dan Xu2 and Luis Martin de Juan2
1
University of Leeds, Leeds, LS2 9JT, United Kingdom
2 Procter
& Gamble, Newcastle Innovation Centre, Newcastle, United Kingdom
The formation of co-crystal or double salt is attracting interest of research due to its important applications
in enhancing physical and chemical properties of final products of crystalline materials, such as stability,
solubility, compressibility and hygroscopicity.[1] Burkeite is an inorganic co-crystal with a wide range of
applications, e.g. it is an essential component of personal care products. Industrial processes precipitate
burkeite isothermally from the solution system while raw material particles of Na2SO4 and Na2CO3 are
dissolving This makes the crystallisation kinetics study using conventional measurement of induction time
infeasible, due to the co-existence of multiple component particles in the system and the varying degree of
supersaturation prior to burkeite precipitation. Therefore, the solution equilibrium and crystallisation kinetics
are difficult to control during the process.
This research employed in-situ Raman technique, with the aid of Chemometrics, to determine the
concentrations of multiple components in their different phases simultaneously as well as to detect the onset of
burkeite precipitation. A new methodology has been developed for fast determination of detailed isothermal
ternary phase diagram of Na2CO3-H2O-Na2SO4 system (e.g. see Figure 1).
The modified KBHR[1,2] approach for nucleation kinetics determination was applied to this isothermal
crystallisation system. The detected metastable zone limits with respect to the phase equilibrium were
correlated to the increase rate of supersaturation during the dissolution of Na2SO4. Using this first principle
model, the nucleation mechanism, interfacial tension and critical size of burkeite nucleus were derived. This
novel strategy could be applied to other systems, offering a fundamental base for modelling nucleation rate
and size control for industrial process of co-crystals.
Figure 1. A Na2CO3-H2O-Na2SO4 ternary phase diagram determined by using in-situ Raman technique
References:
[1] Ainouz, A., Authelin, J.R., et al., Int. J. Pharm. 2009. 374, 82-89.
[2] D.M.C. Corzo, A. Borissova, et al., Cryst.Eng.Comm., 2014, 16, 974
Continuous production of lactose monohydrate crystal seed suspensions by
rapid antisolvent crystallization using a continuous nucleation unit
Pól MacFhionnghaile*, John McGinty, Jan Sefcik
EPSRC Centre for Innovative Manufacturing in Continuous Manufacturing and Crystallisation, Department of
Chemical and Process Engineering, University of Strathclyde, G1 1XJ, Glasgow, UK
[email protected]
A novel continuous nucleation unit was used to produce seed crystals of lactose monohydrate
via rapid antisolvent crystallization. We compared several different solvent-antisolvent systems
with varying solvent mixture compositions. In this study isopropanol, ethanol, and acetone were
used as antisolvents and were continuously mixed with aqueous lactose solutions in a concentric
static mixer setup at a constant temperature.
Due to the design of the nucleator it was possible to observe the solvent-antisolvent mixing
region while being able to vary the flow rates of the inlet streams and through that varying solvent
mixture composition and the overall process flow rate. The fully mixed solutions were feed into a
temperature controlled monitoring vessel for on-line analysis using FTIR spectroscopy, FBRM and
PVM. It was found that by changing key process parameters, such as flow rate and solventantisolvent composition, resulting particle attributes of lactose seed crystal suspensions could be
controlled providing seeds of a desired solid form, particle size and morphology. This approach can
be used to generate seed suspensions in reproducible and scalable manner for seeding of either
batch or continuous crystallization processes.
Monitoring Vessel
V1
Lactose Solution
Pump 1
Mixing
Observable through glass vessel
Pump 3
V2
Antisolvent
On‐line monitoring: Temp., Particle Size (FBRM), Solvent compostion (FTIR), Morphology (PVM) V3
Pump 2
Collection Vessel
Figure 1. Schematic diagram of the nucleation set-up
Off‐line monitoring: Crystallinity (PXRD),
Spectroscopy (ATR‐IR), Particle size and shape (Microscopy, Malvern)
POSTER
S03-P03
Achiral molecules in engineering of non-centrosymmetric crystal structures:
polymorphs and co-crystals of 1H-3,5-dinitropyridine-2-one
Fedyanin Ivan* and Lyssenko Konstantin
A.N.Nesmeyanov Institute of Organoelement Compounds of Russian Academy of Sciences,
Vavilova st. 28, 119991, Moscow, Russian Federation
Organic molecules that have no chiral center tend to crystallize in centrosymmetric space
groups, as this type of packing minimizes the energy of interactions between bond dipoles.
Crystal structure of 1H-3,5-dinitropyridine-2-one (DNHQ) is non-centrosymmetric, in contrast
to its close analogues (e.g. thymine and uracil, space group P21/c). Instead of more common
centrosymmetric dimers, chiral H-bonded chains are the main element of supramolecular
organization in DNHQ. These chains also found in the new polymorph of DNHQ, which has two
symmetrically independent molecules assembled into these chains. Note that in series of co-crystals
of DNHQ with polyaromatic hydrocarbons crystal structures are all non-centrosymmetric. The
chiral chain is therefore the supramolecular synthon that defines the arrangement of DNHQ
molecules in its crystals. The hydrogen bond in polymorphs and co-crystals of DNHQ is bifurcate,
but parameters of the second interaction with oxygen atom of nitro group vary significantly among
crystal structures, as well as properties of weaker stacking and non-specific interactions.
High-resolution X-ray diffraction experiments and ab-initio calculations of crystals and isolated
molecular complexes allowed clarifying the nature of intermolecular interactions, estimate their
energy and overall stability of crystal packing. We propose the possible reasons for noncentrosymmetricity of the structures, and a model for crystallization of the second DNHQ
polymorph that can be only obtained by heteronucleation.
Figure 1. Deformation electron density distribution for intermolecular H-bond in the co-crystal of DNHQ with
phenanthrene.
This study was supported by Russian Foundation for Basic Research, Project No. 14-03-010894
S03-P05
Non-Photochemical LASER-Induced Nucleation in Water/Ethanol of sulfathiazole.
Li Wenjing1,2, Aziza Ikni1,2, Philippe Scouflaire1,3, Shi Xiaoxuan1,2, Nouha El Hassan1,2, JeanMichel Gillet1,2, Anne Spasojević-de Biré1,2*
1
Université Paris Saclay, CentraleSupélec, Campus de Châtenay, Grande Voie des Vignes, 92295
Châtenay-Malabry, France
CNRS, UMR 8580, Laboratory “Structures Propriétés et Modélisation des Solides” (SPMS), Grande Voie
des Vignes, 92295 Châtenay-Malabry, France
3
CNRS, UPR 288, Laboratory “Energétique Moléculaire et Macroscopique, Combustion” (EM2C), Grande
Voie des Vignes, 92295 Châtenay-Malabry, France
2
Crystallization is a crucial in the pharmaceutical industry, due to its importance in the control of the crystal
purity, shape, size distribution and polymorphism, which can affect directly the drug stability, dissolution
and bio-availability. It becomes more and more significant to find an efficient way to control the
crystallization. The non-photochemical laser induced nucleation (NPLIN)1, 2 shows great advantage as an
unusual nucleation method in controlling temporarily and sometimes spatially the crystallization by
manipulating the laser parameters. In order to demonstrate experimentally the feasibility of NPLIN applied
in pharmaceutical molecules, experiments were realized with solutions of sulfathiazole dissolved in
water/ethanol (1:1). Firstly, the solubility curve and metastable zone were measured for the sulfathiazole
solutions, it turns out βc, 25, w/e (168hrs) = 170%. NPLIN succeeded in inducing nucleation of the metastable
solutions within several minutes, the crystal nucleus appears in the interface air/solution. It is found that
there is a dependency of the nucleation efficiency on laser power density and also on supersaturation β of the
sulfathiazole solutions (figure 1a). Furthermore, the experiments implied the number of laser shots effected
directly the obtained crystal number and size, the more laser shots sent to irradiate the solution, the more
crystals were produced and the smaller the crystal size was (figure 1b). Moreover, after characterization of
the obtained crystals by single crystal diffractometer and by Raman diffusion, it is noticed that the linear
polarization favored the formation of polymorph IV, while the circular polarization tended to increase the
proportion of the polymorph III. To study the interaction energy of the sulfathiazole molecule with each
neighbor molecule, a full DFT computation was carried out using the same quantum chemistry model within
the functional density theory framework (M06-2X/cc-PVTZ), available from the Gaussian09 software. This
theoretical calculation reveals, when the form III grows in the direction of the most stable dimer, it will form
a two dimensional crystal packing; while form IV will form a one dimensional crystal packing. This result
confirms the hypothesis that the linear polarization favors the production of form IV while the circular
polarization favors the formation of form III.
CBZ-Acetonitrille-CP
CBZ-Acetonitrille-LP
CBZ-Methanol-CP
CBZ-Methanol-LP
Sulfathiazole-W/E-CP
Sulfathiazole-W/E-LP
Laser power density (GW/cm2)
0,5
0,4
0,3
0,2
0,1
0,0
105
110
115
120
125
130
135
140
Supersaturation (%)
a)
b)
1. CLAIR B., IKNI A., LI W, SCOUFLAIRE P., QUEMENER V. SPASOJEVIĆ - de BIRÉ A. « A new experimental
setup for a high throughput controlled Non-Photochemical LASER-Induced Nucleation (NPLIN). Application to
Glycine crystallization» J. Appl. Crystallogr. 2014, 47, 1252-1260
2 IKNI A., CLAIR B., SCOUFLAIRE P., VEESLER S., GILLET J-M., EL HASSAN N., DUMAS F., SPASOJEVIĆ de BIRÉ A. «Experimental demonstration of the carbamazepine crystallization from Non-Photochemical LASERInduced Nucleation in acetonitrile and methanol » Cryst. Growth & Design, 2014, 14(7) 3286-3299
S03-P06
Purification of fermentatively produced specialty carbohydrates
Bekers Katelijne Maaike*, Moens Helena, Vanlerberghe Brecht, Waegeman Hendrik
Bio Base Europe Pilot Plant, Rodenhuizekaai 1, Gent (Belgium)
Specialty carbohydrates are of high interest for industrial applications. Because of their role in
human biology, many areas could benefit from their multiple health benefits. Especially cosmetic,
pharmaceutical and nutraceutical markets have high potential.
However, the production of specialty carbohydrates for industrial use by chemical synthesis is
unsuitable. The developed processes have major issues with stereoselectivity, complex and
expensive techniques for purification and the use of toxic compounds. Production is therefore not
economic viable and especially for nutraceutical applications the use of toxic compounds is
unwanted or even prohibited. Enzymatic synthesis has the benefit of using more specific reactions
and less harsh conditions, but still the complexity of the molecules and purification remain a
tremendous hurdle to tackle.
Because of these issues, biotechnological routes to produce specialty carbohydrates are
currently developed. Whole cells have been metabolically engineered to produce different
monosaccharides or oligosaccharides of interest, starting from a supplied precursor. The cells are
engineered as such that metabolic pathways involved in the degradation of the precursor are
eliminated and the production of by-products strongly reduced. By doing so, the precursors are
efficiently and directly converted into the desired product. By using a fermentation process, a cost
and time effective process can accordingly be developed, allowing an interesting economy of scale
with industrial compatible cost and yield for different specialty carbohydrate targets.
Bio Base Europe Pilot Plant (BBEPP) is involved in the optimization and scale-up of the
fermentation process and downstream processing of the production of specialty carbohydrate. One
of the issues in their process development that is currently addressed by BBEPP, is the
underdeveloped downstream process (DSP). The process economics would benefit significantly if a
crystallization process could be applied.
This poster presentation will give an overview of different strategies applied and the equipment
used by BBEPP for development, scale-up and demonstration of product recovery and purification.
With this, it will discuss the opportunities and challenges in applying crystallization for the product
recovery and purification of monosaccharides an oligosaccharides from fermentation broth.
S03-P12
Crystallisation Characteristics of an Organic Material in Industrial Mother
Liquor with Impurities
Khan Shahid 1, Mahmud Tariq*1, Roberts Kevin 1, Zhu Xiaofeng 1, George Neil2 and Sillers
Pauline2
1
Institute of Particle Science and Engineering, School of Chemical and Process Engineering, The University of Leeds,
Leeds LS2 9JT, UK
2
Syngenta, Jealott's Hill International Research Centre, Bracknell, Berkshire RG42 6EY, UK
In pharmaceutical and fine chemical industries, the isolation and purification of organic
materials are commonly carried out using various solution crystallisation techniques including the
batch cooling crystallisation process. In industrial crystallisation processes, mother liquors usually
contain unwanted dissolved molecules (generally referred to as impurities) produced via reaction
steps prior to the crystallisation and their concentration may vary from batch to batch. It has long
been established that the supersaturation driven nucleation and crystal growth rates can change
profoundly even in the presence of low levels of impurities added intentionally to or inherently
present in the solution, and thus affects the size, shape and purity of the product crystals. This could
also impede efficient downstream processing of crystals such as filtration, drying and milling. In
order to control industrial crystallisation processes to meet product specifications, such as narrow
crystal size distribution, high chemical purity and desired crystal morphology, with high product
yields, it is important to develop a detailed understanding of the crystallisation characteristics of
product materials in the mother liquors containing process generated impurities. This can be
achieved via replicating the industrial process at laboratory scales in the presence of impurities.
The work reported here investigated the crystallisation behaviour of an organic material
(referred to as compound A due to confidentiality) from an industrial mother liquor (which mainly
contains an organic compound), corresponding pure solvent and the pure solvent doped with the
process generated impurity as a function of representative processing variables, e.g., level of
impurities, seeding and cooling profile. Experiments were carried out in a 500 mL jacketed glass
stirred tank crystalliser with temperature controlled using Julabo FP50-HD thermostatic bath. The
metastable zone width and induction time for the nucleation of compound A were determined using
a turbidimetric method as a function of both cooling rate and solute concentration in the pure and in
impurity added solvent. ATR-FTIR spectroscopy coupled with a PLS calibration model was used
for on-line monitoring and control of supersaturation during the batch cooling crystallisation of
compound A.
The metastable zone width was found to be wider in the mother liquor and in the solvent doped
with impurity compared with that in pure solvent. The induction time for nucleation of compound A
increases with increasing impurity concentration. A significant outcome of this research is reflected
in the observations that the crystals produced in pure solvent have a much different physical form
compared to those crystallised from mother liquor. The former crystals tend to be smaller and
heavily agglomerated when compared to the latter which display superior crystal quality and
external morphology. The latter perhaps is a reflection of the nucleation and solubilisation abilities
of the other components present in the mother liquor. However, in the pure system, particles
spontaneously nucleated at much higher supersaturation levels leading perhaps to an excessive
primary nucleation rate resulting in smaller and more agglomerated crystals.
SESSION 4
Bulk Crystal Growt
A new large-lattice-constant perovskite substrate crystal
Uecker, Reinhard*1, Klimm, Detlef1, Bertram, Rainer1, Guguschev, Christo1, Brützam, Mario1,
Kwasniewski, Albert1, Klupsch, Michael1, Gesing, Th.M.2, Schlom, D.G.3
1
Leibniz Institute for Crystal Growth, Max-Born-Str. 2, D-12489 Berlin (Germany)
University of Bremen, Solid State Chemical Crystallography /FB02, Leobener Str. /NW2, D-28359 Bremen
(Germany)
3
Department of Materials Science and Engineering, Cornell University, 230 Bard Hall, Ithaca, NY 14853-1501 (USA)
2
A broad range of bulk oxide crystals with cubic and pseudo cubic perovskite structure is used as
substrates for the epitaxy of high quality perovskite thin films with targeted strain. Such strain
engineering allows the enhancement or total change of the properties of functional oxides. LuAlO3
has the smallest lattice constants of the commercially available oxide perovskites (3.67 Å) whereas
the discovery of new thin films continuously requires new substrates with larger lattice constants.
For several decades the universal SrTiO3 has been that employable perovskite-type substrate with
the largest lattice constant (3.90 Å). First the introduction of the rare earth scandates LnScO3
(Ln=Dy-La) shifted the upper limit to 3.95-4.05 Å. However, with CeScO3 and LaScO3 the largest
of them are excluded from Czochralski growth -the most appropriate method for the growth of high
perfection bulk crystals- because of their exceptional high melting temperature (>2250 °C).
Therefore, PrScO3 with 4.02 Å forms the end of this range. I.e., the large number of 17 different
substrates covers a lattice constant range of 0.35 Å (3.67-4.02 Å). This dense occupation enables a
very precise tuning of film properties in this region by strain engineering. Notwithstanding that
several oxide perovskites having larger lattice constants are reported, so far only one could be
grown as bulk crystal: LaLuO3 (4.17 Å). That means there is a serious lack of larger-lattice-constant
perovskites to be used as substrate crystals for advanced new thin films.
To discover new perovskites in this region which can be grown as bulk crystal, the pseudo
binary phase diagram of the above edge components LaScO3-LaLuO3 was systematically
investigated. In the result solid solution formation was found close to the 1:1 composition. The
liquidus temperature is below 2200 °C which allows the growth by the Czochralski method from an
iridium crucible. This solid solution exhibits an interesting structure: Because the Lu ion can
occupy both, the position of the large A cation and that of the smaller B cation in the perovskite
cell, a few percent of it were proven to occupy besides B also a few A sites. Thus the formula of the
Czochralski grown bulk crystal is (La1.94,Lu0.06)(Lu1.11Sc0.89)O6. It shows a pseudo cubic lattice
constant of about 4.12 Å, i.e., it fits exactly into the gap between PrScO3 and LaLuO3. Because of
the low segregation, the shift of the lattice constants over the crystal length is rather small.
Therewith, for the first time an excellent substrate crystal for highly topical films like BaSnO3
(transparent semiconducting oxide), BiScO3 (piezoelectric with high temperature stability) and
PbZrO3 (interesting antiferroelectric) could be made available.
Floating-zone Growth of Large Single-Crystal of Haldane Chain Compound
SrNi2V2O8
A.T.M. Nazmul Islam*1, B. Lake1, A.K. Bera1, B. Klemke1, E. Faulhaber2, J.M. Law3, A.
Schneidewind4, J.T. Park5, E. Wheeler6
1
Helmholtz-Zentrum Berlin für Materialien und Energie, D-14109 Berlin (Germany)
Helmholtz-Zentrum Berlin für Materialien und Energie, Gemeinsame Froschergruppe, D-85747 Garching (Germany)
3
Hochfeld Magnetlab Dresden, Helmholtz-Zentrum Dresden-Rossendorf, D-01314 Dresden (Germany)
4
Jülich Center for Neutron Science JCNS, Froschungszentrum Jülich GmbH, Outstation at MLZ, D-85747 Garching
(Germany)
5
Heinz Maier-Leibnitz Zentrum, TU München, D-85747 Garching (Germany)
6
Institut Laue-Langevin, Boite Postale 156, 38042 Grenoble Cedex (France)
*[email protected]
2
Low dimensional quantum magnets are a special class of material sought by condensed matter
physicists, since they show exotic magnetic behaviors. Haldane in his pioneering work predicted
that one-dimensional (1D) Heisenberg antiferromagnet systems with integer spin will show a singlet
ground state and a gapped excited state known as the Haldane gap, whereas half-integer spin chains
will have a spin-liquid ground state with gapless spinon excitations. ANi2V2O8 (A=Pb, Sr) whose
structure has magnetic Ni2+ ions with spin S=1 arranged in a screw chain along the c-axis forming a
quasi 1D spin-chain structure, is an ideal candidate to study the integer spin Haldane chain. These
materials provide fertile ground to investigate the effect of the inter-chain interactions and single
ion anisotropy on the Haldane state. In addition they can be tuned through a quantum phase
transition to long-range magnetic order via application of a magnetic field. Large and high quality
single crystals of these compounds are essential for such studies. However, ANi2V2O8 (A=Pb, Sr),
is a incongruently melting compound of three oxides AO (A=Sr,Pb), NiO and V2O5 among which
the phase relationship is not well understood. So, despite continual interest, more than a decade
after the discovery of ANi2V2O8 (A=Pb, Sr), there is no report on single-crystal growth of either
compound. We think the challenge lies in finding a suitable flux composition for growth of such a
complex multinary compound. In this work we report the first growth and characterization of a
large single crystal (~25mm in length and ~5 mm in diameter) of SrNi2V2O8 by Traveling solvent
floating zone method in an IR heated Floating-zone furnace.
Europium and potassium co-doped strontium metaborate single crystals grown by the
Czochralski method
Głowacki Michał 1*, Solarz Piotr 2, Ryba-Romanowski Witold 2, Martín Inocencio R. 3, Diduszko Ryszard 1,4, Berkowski
Marek 1
1 Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw (Poland)
2 Institute of Low Temperature and Structure Research, Polish Academy of Sciences, ul. Okólna 2, 50-950 Wrocław (Poland)
3 Departamento de Física, Instituto de Materiales y Nanotecnología (IMN),Universidad de La Laguna, Av. Astrofísico Francisco
Sánchez, s/n E-38206 La Laguna, Tenerife (Spain)
4 Tele and Radio Research Institute, Ratuszowa 11, 03-450 Warsaw Poland
*e mail: [email protected]
Strontium borates are suitable materials for use as matrices for luminescent dopant ions. Several
published reports have been devoted to doping strontium metaborates with europium [1-2], but the
results were inconsistent. To elucidate the ambiguity of available information we undertook
attempts to grow good quality SrB2O4 single crystals and investigate the light emission from both
Eu2+ and Eu3+ ions that occur in this host. Divalent europium ions give rise to an UV–blue
luminescence, while the trivalent ones– to a red luminescence. As a consequence the materials
under study are promising phosphors for white light emission applications.
Recent studies on europium doped strontium borates [3] have shown that the europium emission
is more efficient when the host matrix is co-doped with alkali ions. In this presentation we report on
the first successful growth of strontium metaborate single crystals co-doped with europium and
potassium by the Czochralski method and on their structural and spectroscopic features. In
particular, results of optical gain measurements using pump and probe method will be presented and
discussed.
a)
b)
Figure 1. As-grown SrB2O4 single crystals (a) and their diffraction patterns (b)
Acknowledgements:
The work was funded by the Polish National Science Center (NCN) on the basis of the decision number
DEC-2013/09/D/ST5/03878
References:
[1] K. Machida, G. Adachi, J. Shiokawa, M. Shimada, M. Koizumi, J. Lumin. 21 (1980) 233-237
[2] H. J. Seo, B. K. Moon, B. J. Kim, J. B. Kim, J. Phys: Condens Matter 11 (1999) 7635-7643
[3] Hua-Yu Zhu, Yin-Wen Li, Li Zhang, Shou-Li Suo, Al-De Sun, Man-Geng Lu, Optoelectr. Adv.
Materials 6 (2012) 555-559
Flux growth and characterization of highly Yb3+-substituted cubic RE2O3
(RE=Gd, Y, Lu) laser crystals and of cubic Lu1.56Gd0.41Eu0.03O3 crystals
Matias Velázquez*1, Philippe Veber1, Gabriel Buşe1, Yannick Petit1, Philippe Goldner2, Olivier
Plantevin3, Daniel Rytz4, Emmanuel Véron5, Rekia Belhoucif6, Véronique Jubera1, Patrick
Aschehough2, Gérard Aka2
1
CNRS, Université de Bordeaux, ICMCB, UPR 9048, 87 avenue du Dr. A. Schweitzer, 33608 Pessac cedex (France)
PSL Research University, Chimie ParisTech – CNRS, Institut de Recherche de Chimie Paris, 75005 Paris (France)
3
CSNSM, UMR 8609 CNRS-Université d’Orsay, Bât. 108, 91405 Orsay Campus (France)
4
FEE-GmbH, Struthstrasse 2, 55743 Idar-Oberstein (Germany)
5
CEMHTI-CNRS UPR 3079, 1D Av. de la Recherche Scientifique, 45071 Orléans (France)
6
Faculté de Physique, Laboratoire d’Électronique Quantique, USTHB, BP 32 El alia, 16111 Bab Ezzouar, Alger (Algeria)
2
Developing large optical grade cubic rare-earth sesquioxides (RE2O3, RE=Sc, Y, Gd, Tb,
Lu) single crystals, pure or doped with Yb3+ ions stands as one of the most challenging endeavours
of today’s crystal growth [1]. This is essentially due to the high melting point of these compounds
(~2400-2500°C) and because of a series of structural phase transitions occurring upon cooling for
some of them, as Gd2O3 or Tb2O3. In this work, we will present highly Yb3+-substituted Gd2O3,
Y2O3 and Lu2O3 single crystals of the cubic phase with dimensions of several mm³ which were
recently grown by a newly designed high-temperature solution growth method [2,3]. Furthermore,
we will report on their characterization by means of X-ray diffraction, visible, near infrared and
Fourier transformed infrared (FTIR) spectroscopy, electron probe microanalysis (EPMA) coupled
with wavelength dispersive spectroscopy (WDS), exhaustive and complete chemical analysis by
GDMS, emission spectroscopy and Squid magnetometry. Our solution growth method uses an
original and nontoxic solvent with a growth setup operating in air between 1250°C and 1100°C, that
is, at half the melting temperature of rare-earth sesquioxides. The high-temperature solution growth
conditions and two thermodynamic features of the solvent will be discussed. Indeed, not only cubic
Gd2O3 single crystals had never been grown before, but Yb3+-substitution levels as high as
Gd1.61Yb0.39O3, Y1.69Yb0.31O3 and Lu1.86Yb0.14O3 were remarkably reached. In addition to
demonstrating that this flux growth process allows the obtention of optimal doping for high-power
laser applications, we will emphasize that it impedes the dissolution of OH- groups in the crystals,
avoids the reduction of Yb3+ ions into Yb2+ without resorting to any post-growth thermal annealing,
hinders the Yb-pairs formation kinetics in Y2O3 crystals and, last but not least, favours broader
absorption and emission bands. Laser operations were demonstrated with uncoated and uncooled
Yb3+-doped cubic Gd2O3 and Y2O3 crystals [4]. We will also show and discuss our latest ~0.5 cm3
cubic Lu1.56Gd0.41Eu0.03O3 scintillator crystal, the crystal habit and physical properties of which
were fully characterized by Laue X-ray diffraction, absorption and emission spectroscopies and
magnetic susceptibility measurements.
References:
[1] A. Yoshikawa, V. Chani, MRS Bulletin, 34 (2009) 266.
[2] Ph. Veber, M. Velázquez, V. Jubera, S. Pechev, O. Viraphong, Cryst. Eng. Comm. 13 (16)
(2011) 5220-5225.
[3] M. Velázquez, Ph. Veber, G. Buşe, Y. Petit, Ph. Goldner, V. Jubera, D. Rytz, A. Jaffres, M.
Peltz, V. Wesemann, P. Aschehough, G. Aka, Opt. Mater., 39 (2015) 258-264.
[4] F. Druon, M. Velázquez, P. Veber, S. Janicot, O. Viraphong, G. Buşe, M. Abdou Ahmed, T.
Graf, D. Rytz, P. Georges, Opt. Lett., 38(20) (2013) 4146–4149.
On the crystal growth of incongruent borate type crystal LaxGdyScz(BO3)4 (x + y
+ z = 4) by the Czochralski method
Lucian Gheorghe1, Flavius Voicu1, Gabriela Salamu1, Federico Khaled2, Alexandru Achim1, Cristina
Gheorghe1, Pascal Loiseau2, Nicolaie Pavel1, Gérard Aka2
1
2
National Institute for Laser, Plasma and Radiation Physics - LSSQE, Magurele-Bucharest, Romania
PSL Research University, Chimie ParisTech – CNRS, Institut de Recherche de Chimie Paris, 75005 Paris, France
Some of the most important NLO crystals that are used in current commercial applications
include KTiOPO4 (KTP), KH2PO4 (KDP), KD2PO4 (DKDP), β-BaB2O4 (BBO), YAl3(BO3)4
(YAB), LiB3O5 (LBO) and periodically poled LiNbO3 (PPLN). Despite of the wider usage,
essentially all of these crystals melt incongruently with the exception of LiNbO3, so they all have to
be grown by flux method, which makes them expensive and limited in size most often. So, the
feasibility to produce large NLO crystals at low cost is highly desirable, especially for high-power
or high-energy frequency conversion applications.
LnSc3(BO3)4 (Ln = lanthanide) borates crystallizes in different allotropic forms depending on
the ratio of the ionic radii of Ln and Sc (rLn/rSc). For example, for Ln = La, LaSc3(BO3)4 - LSB
crystal is centrosymmetric (monoclinic structure, space group C2/c) and therefore optically linear,
while for Ln = Gd, GdSc3(BO3)4 - GSB crystal is isostructural with non-centrosymmetric trigonal
huntite mineral CaMg3(CO3)4 (space group R32) and consequently optically nonlinear [1]. Recently
it was demonstrated that the monoclinic structure of LSB can be converted to the trigonal form by
doping with smaller Gd3+ ions, and LaxGdyScz(BO3)4 (x + y + z = 4) - LGSB nonlinear crystals
were grown by the top seeded solution growth method (TSSG) from a flux of Li6B4O9-LiF [2].
Even though LSB present a non-congruent melting behaviour, it can be grown by the Czochralski
method if the starting material contains an excess of LaBO3. Therefore an attempt of growing good
quality and large size crystals of LGSB by the Czochralski method was undertaken. Also, the
doping with luminescent ions was investigated for self-frequency doubling applications.
XRD and DTA analysis were performed in order to determine both the limits of the solid
solution of LaxGd1-xSc3(BO3)4 with space group R32 and the most efficient composition of the flux.
The crystal growth parameters were then optimized and relatively large size (about 10 mm in
diameter and 30 mm in length) crystals of LGSB and Yb:LGSB of high quality were grown by the
Czochralski method for the first time (Fig. 1). The optical properties of the grown crystals were
evaluated and the spectroscopic and infrared laser emission properties of Yb:LGSB crystals were
characterized. All these features suggest that pure and Yb-doped LGSB crystals have great potential
for high-power NLO applications.
Figure 1. The photographs of LGSB (left) and Yb: LGSB (right) grown crystals.
References
[1] S. T. Durmanov, O. V. Kuzmin, G. M. Kuzmicheva, S. A. Kutovoi et al., Opt. Mater., 18 (2001)
243.
[2] Xiang Xu, Ning Ye, J. Cryst. Growth, 324 (2011) 304.
Improvement of crystal growth of Li4SiO4 single crystals for neutron detection
and their scintillation and luminescence properties
Jan Pejchal*1, Vladimir Babin1, Alena Beitlerova1, Shunsuke Kurosawa2,3, Yuui Yokota2,3,
Akira Yoshikawa2,3, Martin Nikl1
1
Institute of Physics CAS , Cukrovarnicka 10, Prague 6 (Czech Republic)
Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai (Japan)
3
New Industry Creation Hatchery Center, 6-6-10 Aoba, Aramaki, Sendai (Japan)
2
Neutrons have recently become essential probes in material research on both macroscopic and
microscopic scale. They can be applied in various imaging techniques or scattering techniques to
investigate material or molecular structure and others [1]. Possible applications in security systems
or oil well logging can be considered as well.
We have investigated Li4SiO4 scintillation crystals for their possible application in neutron
detection due to high Li content, which would enable a sufficient probability of interaction of the
material with a neutron, and low density of 2.35g/cm3, which is important for lowering the
background gamma-ray sensitivity. Its lower melting point (1250 °C) might enable incorporation of
Ti3+ without being oxidized to Ti4+. Then, the Ti3+ 3d-3d luminescence in red spectral region, which
matches the sensitivity of contemporary photodiodes, might be exploited. The micro-pulling-down
method [2,3] employing the Ir crucible and afterheater was optimized for crystal growth of Li4SiO4
taking into account the incongruent Li evaporation. Moreover, it was found that increased heating
power led to milder temperature gradient, thicker meniscus, smaller crystal diameter and resulting
smaller tension in the as-grown crystals. This allowed us to grow high-quality crack-free single
crystals. The undoped, Ti-, Cr-, Mn- and Al- doped crystals were prepared and studied. Preliminary
radioluminescence measurements under X-ray excitation showed quite high overall scintillation
efficiency of the Ti-doped sample reaching as high as 250% of that of Bi4Ge3O12 reference
scintillator. The emission spectrum was dominated by one broad band peaking at 350 nm,
tentatively ascribed to Ti4+ charge transfer luminescence. Reasonable light yield of
10000 photons/neutron was found. However, its long decay time of 54 μs might be a limitation
especially for high counting rate applications. The overall scintillation efficiency of the Cr3+ sample
was much lower and the spectrum shows one broad peak at 463 nm with a decay time around 10 μs,
which are characteristics not corresponding to those of Cr3+ ion. This means that another
luminescence process takes place. The efficiency of the Mn-doped sample was slightly higher and
the spectrum consisted of two broad bands at 442 nm and 680 nm. The latter one was characterized
by a long decay time of 5 ms which would correspond to the Mn4+ luminescence. The origin of the
442 nm one with much faster decay in the order of microseconds is not clear. On the other hand, the
radioluminescence spectrum of the Al-doped sample closely resembled to that of the Ti-doped one,
just its magnitude is considerably lower. The similarity of the temperature dependences of
photoluminescence spectra and decay time for these two samples might suggest that Ti might be
stabilized still as a trivalent ion and an unusual luminescence mechanism might take place for the
trivalent dopants. Peculiarities and optimization of crystal growth and a preliminary sketch of
luminescence mechanism and dopant incorporation will be presented and discussed.
References:
[1] van Eijk C. W. E., Radiation Measurements 38 (2004) 337
[2] Yoshikawa A., Nikl M., Boulon G., Fukuda T., Opt. Mater. 30 (2007) 6
[3] Yoshikawa A., Chani V. I., MRS BULLETIN 34 (2009) 266
Synthesis and characterization of Ba2Cu1-xNixGe2O7, x =0, 0.1 single
crystals grown by floating zone technique
Fittipaldi Rosalba1,2, Rocco Luisa1, Ciomaga Hatnean Monica3, Granata Veronica*1,2, Lees Martin3,
Balakrishnan Geetha3, Vecchione Antonio1,2
1
Department
of Physics, University of Salerno, Fisciano (Sa) (Italy)
CNR-SPIN Salerno, Fisciano (Sa) (Italy)
3
Department of Physics, University of Warwick, Coventry, (United Kingdom)
2
In recent years, the understanding of the multiferroic properties, i.e. of the simultaneous
presence of two or more coexisting ferroic orders, has been the topic of increasing interest. The
attention to multiferroics has been mainly driven by the large magnetoelectric (ME) coupling shown
by some distorted perovskites of transition metal (TM) oxides displaying both ferroelectric and
magnetic properties. The study of the helimagnet Ba2CuGe2O7 is of great interest among the class
of multiferroic compounds because it has been predicted that it could host a lattice of magnetic
skyrmions. The study of all these complex phenomena requires the availability of good crystals. In
this study high quality Ba2Cu1-xNixGe2O7 single crystals has been grown using the floating zone
(FZ) technique, in different gas atmospheres and pressures. The excellent quality and perfect
orientation of the crystals were confirmed by high resolution X-ray diffraction measurements. In
Fig. 1 is shown the rocking curve of the (0 0 2) reflection proving the high crystallinity of the grown
Ba2Cu1-xNixGe2O7 (x = 0) crystals. The crystals were also inspected by electron back scattered
diffraction technique, these measurements allow to ascertain the absence of any misorientation on a
microscopic scale supporting the results from X-ray measurements. XRD patterns and Rietveld
refinement of crushed crystals showed diffraction peaks, all of which could be indexed to the
Ba2Cu1-xNixGe2O7 phase, which means that crystals are pure. Compositional analysis has been
carried out by WDS and they, also, put in evidence that the crystals don’t have spurious phases. The
obtained crystals showed being suitable exploring the complex magnetoelectric phase diagram.
Synthesis of large single crystals allows to investigate the fundamental physics of this material in
order to identify the mechanisms responsible for its peculiar multiferroic properties.
Figure 1. Rocking curve of the (0 0 2) reflection acquired on Ba2Cu1-xNixGe2O7 (x = 0) single crystal
Crystallization of Al2O3-YAG-ZrO2 eutectic ceramic plates by the EFG
technique
Laurent Carroz1, 2, Maya Cherif1, 3, Nicolas Barthaley2, José Peirrera2 and Thierry Duffar*3
1
2
3
The growth of eutectic oxides from the melt has been widely studied in the last decades. Indeed,
due to their very specific 3D interconnected microstructure these materials offer exceptional
mechanical properties at very high temperature [1]. Growth techniques (Bridgman, µ-pulling down,
laser floating zone) and samples size obtained are still very varied according to laboratories, but
currently, the Edge – defined Film – fed Growth (EFG) process was never mentioned to grow large
crystals with adequate conditions for industrial production. Since the EFG technique allows
growing shaped crystals directly from the melt, expensive and difficult post machining operations
for these very hard materials can be avoided. Thus EFG process is an adequate growth technique for
industrial crystal grower.
In this context Al2O3-YAG-ZrO2 eutectic ceramic plates (cf. figure 1) were crystallized with the
EFG process in Mo crucible and shaper, using an automated weight control system. Growth
parameters had to be adjusted to maintain the shape while making sure to get a homogeneous 3D
interconnected microstructure (cf. figure 1).
Figure 1. Al2O3-YAG-ZrO2 eutectic ceramic plates crystallized by the EFG technique and its interconnected
microstructure as shown by SEM metallography.
References:
[1] Y. Waku, Mechanical Properties and Thermal Stability of Oxide eutectic Composites at High
Temperatures, Materials and Manufacturing Processes, 13 (1998), 6, 841-858.
New results in adsorption at semiconductor surfaces - consequences to growth
and doping of semiconductor from the vapor
Stanisław Krukowski*1, Pawel Kempisty1, Pawel Strąk1, Maria Ptasinska2, Jacek Piechota2
1
1Institute of High Pressure Physics, Polish Academy of Sciences, Sokołowska 29/37, Warsaw (Poland)
Interdisciplinary Centre for Materials Modelling, Warsaw University, Pawińskiego 5a, Warsaw (Poland)
2
Results of ab initio simulations of adsorption of molecular and atomic species at semiconductor
surfaces are discussed. A number of the growth species, including ammonia, hydrogen, silicon
attachments to several semiconductor surfaces, such as GaN(0001), GaN(0001), AlN(0001) and
SiC(0001) is discussed. A newly identified dependence of the adsorption energy on the charge
transfer at the surface is identified and discussed. The DFT results necessary for the in-depth
analysis of the processes are presented. It was proven that the adsorption energy, in addition to
standard bonding term, is potentially supplemented by the electronic transfer contribution
depending on the Fermi level. Thus the adsorption energy may vary by several electronvolts,
depending on the Fermi level at the surface. It is shown that the predominant cases of the growth of
semiconductor occurs in the condition when Fermi level is unpinned becoming free. Such surface
state is may be analyzed using extended electron counting rule (EECR). In such condition the
adsorption energy depends on the Fermi level position in the bulk, i.e. doping of the bulk
semiconductor. The dependence of the adsorption energy on the Fermi level in the bulk provides
basic explanation of the doping of semiconductors during growth. In addition, the atomic level
mechanism of the transition of adsorption sites, incompatible to the crystal lattice, frequently
obtained in ab intio simulations of the species at the semiconductor surfaces may be explained by
electronic charge transfer. The results indicate that semiconductor crystal growth grow by the
mechanism that is different from standard Burton, Carbera Frank (BCF) model.
Range of the temperature gradients and the growth rate values in the growth of
CZT crystals from the melt
Repiso Eva1, Corrochano Álvaro1, Rubio Sandra1, Plaza Jose Luis1, Tsybrii Zinoviia2, Vuichyk
Mykola2,Dieguez Ernesto*1
1
Depart: Physics of Materials, Universidad Autónoma de Madrid (UAM), Madrid (Spain)
2
Institute of Semiconductor Physics (ISP), Kiev, (Ukraine)
CdZnTe bulk crystals have been broadly employed in room temperature X-ray and gamma ray
semiconductor detector applications due to their attractive physical-chemical material properties, in
particular the high energy detection as an important parameter in medical imaging and homeland
security applications. The presence of secondary phases, Te inclusions, dislocations, Cd vacancies,
polycrystallinity, etc. are common facts that may cause the detector degradation, but that it can be
reduced by adequate growth conditions. In fact, although it´s possible to build CdZnTe compact
detectors for their use in the above mentioned applications, a tight control of a number of crystal
growth parameters is needed to obtain high quality single crystal CdZnTe materials.
The most often methods for growing large CZT crystals from the melt are Bridgman and
Vertical Gradient Freeze techniques. Although they are both well-developed techniques, the lack of
complete information about the growth parameters is a general fact in the publications on this field.
For this reason, in this work we plan to validate the two most important growth parameters such as
the growth rate (V) and the temperature gradients (G) in the solid (s) and in the liquid (l) in view of
the heat balance equation in the solid liquid interface (SLI), taking into account known values for
the thermal conductivities of the solid and the liquid (Ks, Kl).
The range of the Gs and Gl versus V was examined by analyzing both experimental and
simulated data obtained in the VGF technique. The Gs/V versus Gl/V representation gives a straight
line where the slope is given by the ratio of the thermal conductivities Kl/Ks, being the range for an
adequate V crystal growth value deduced from this figure. Moreover, the dependence of G in the
solid and in the liquid on the V value shows that Gl has a negative dependence with V, while Gs
linearly increases with the growth rate, giving the ratio of the Gs and Gl values the same as Kl/Ks
when the growth rate is zero. Furthermore, the dependence of the product of thermal conductivities
and the thermal gradient in the solid and in the liquid (KsGs, KlGl) on the growth rate shows that
when V increases, Gl decreases and Gs increases to offset the product of LV. A complete view of
the dependence of G on V using own and published experimental data, together with simulation
results will be analyzed in this paper.
References:
[1]A. Natsume, N. Inoue, K. Tanahashi, A.Mori, Journal of Crystal Growth, 225 (2001) 221-224.
[2] H. Bensalah, J.L. Plaza, J. Crocco, Q.Zheng, V. Carcelén, A. Bensouici, E. Diéguez, Applied Surface
Science, 257 (2011) 4633-4636
Growth and Performance of Large ZnGeP2 Single Crystals
Chunhui Yang*, Zuotao Lei, Chongqiang Zhu, Liangcheng Song
Harbin Institute of Technology, No.92 West Da-Zhi Street Nan Gang District, Harbin (China)
Zinc germanium diphosohide (ZnGeP2) belongs to the chalcopyrite family with a direct band
gap, and it has large nonlinear optical coefficient, a wide transparency range, sufficient
birefringence and relatively high thermal conductivity[1]. All these physical properties make
ZnGeP2 suitable for frequency conversion applications such as tunable mid and far-infrared optical
parametric oscillator (OPO) laser systems.
Firstly, ZnGeP2 polycrystalline ingots were synthesized by two-temperature method, and the
maximum mass is about 500g for one run. The XRD and rocking curve suggest that they show
chalcopyrite structure, high pure and good crystallinity. The ingots are suitable for growth as raw
materials. Moreover, the study indicates that the more the charge amount, the higher the yield of
product.
Secondly, ZnGeP2 crystals were grown by Vertical Bridgman technique, and the largest size is
about Φ50mm×140mm. The XRD and rocking curves suggest that they show good crystallinity and
single phase, the XRF indicates that the as-grown ZnGeP2 is stoichiometric, and the absorption
coefficients of as-grown ZnGeP2 are 0.05-0.08cm-1 at 2.05µm for o-light. However, the absorption
coefficients of annealed and irradiated ZnGeP2 reduce to 0.01-0.03cm-1 at 2.05µm for o-light. The
crystals are suitable for frequency conversion applications.
Finally, the ZnGeP2 devices were tested for OPO. The ZnGeP2 crystals were cut to
6mm×6mm×(16-24)mm in sizes after thermal annealing. Both surfaces of the crystal were carefully
polished and antireflection coated for pump, signal, and idler lights. The OPO output wavelengths
were in the spectral range of 3-5 mm. The results suggest that the output power of 30W is obtained
pumping at 2.09µm and the conversion efficiency is 56%[2]. Thus, ZnGeP2 is an excellent OPO
material and is acceptable for the fabrication of the infrared nonlinear optical devices.
Figure 1. Typical ZnGeP2 devices with size of 6×6×(16-24)mm)
References:
[1] Shay J L and Wernick J H, Pergamon Press, (1975) 1-244.
[2] Zuotao Lei, Chongqiang Zhu, Chao Xu, Baoquan Yao, Chunhui Yang, Journal of Crystal Growth,
389(2014) 23-29.
Crystal growth, physical properties and applications of mixed and complex
halides
Edith Bourret*, Zewu Yan, Eric Samulon, Tetiana Shalapska and Didier Perrodin
Lawrence Berkeley National Laboratory, 1 Cyclotron Rd, Berkeley CA (USA)
The ability to make new materials is often key to major progress in fundamental physics and
numerous applications. The field of scintillation is no exception. The pace of discovery of new
scintillators has increased dramatically in the last few years after the discovery at the Lawrence
Berkeley National Laboratory of efficient scintillation in new mixed and ternary halides [1-3]. Due
to their property to emit light due to radiation interactions, these materials find uses in a variety of
applications that such medical imaging, high energy physics experiments, mining and security. We
will show that these materials are close to the fundamental limits in terms of luminosity, energy
resolution, stopping power and response time. However they are often needed in the form of single
crystals of large dimensions that is a challenge to achieve. We will present the current state of the
growth of single crystals of mixed and complex halides. In particular we will discuss the issues
stemming from raw materials purity, the hygroscopic nature of the compounds, the propensity to
fracture during cooling and their phase diagrams. Mixed Ba halides are fully miscible and melt
congruently. Figure 1 is an example showing a single crystal of BaBrCl, a mixed halide, with the
melting/solidification behavior of that compound. Complex halides exhibit a variety of growth
behavior. Results of engineering techniques aimed at improving the quality and performance of the
single crystals will be discussed.
Figure 1. BaBrCl single crystal as grown (top) and under UV illumination (bottom) and the phase diagram of the solid
solutions of BaBr2-BaCl2.
References:
[1] ] E. D. Bourret-Courchesne, G. Bizarri, R. Borade, G. Gundiah, E.C. Samulon, Z. Yan, and S. E.
Derenzo, Journal of Crystal Growth, 352 (2012) 78-83.
[2] E. D. Bourret-Courchesne, G. Bizarri, S. M. Hanrahan, G. Gundiah, Z. Yan, and S. E. Derenzo,
NIM A, 613 (01/21/2010) 95-97.
[3] G. Bizarri, E. D. Bourret-Courchesne, Z. W. Yan, and S. E. Derenzo, IEEE Transactions on Nuclear Science, 58
(2011) 3403.
Modeling of dopant transport in gas and melt during silicon FZ crystal growth
Sabanskis Andrejs*1, Surovovs Kirils1, Virbulis Jānis1
1
Faculty of Physics and Mathematics, University of Latvia, 8 Zellu str., LV-1002, Riga (Latvia)
The radial resistivity variation (RRV) is one of the most important quality criteria of a FZ
grown single silicon crystal. The resistivity is controlled by adding dopants (impurities) to silicon,
which are either incorporated in the feed rod or supplied though the atmosphere. The former case is
considered in [1,2], while the latter, which is the most common nowadays, in [3]. However, a
simplified concentration boundary condition is used in [3] at the free melt surface to model doping
from the atmosphere, not considering dopant transport in gas.
In the present work a 3D model for the calculation of dopant transport in gas in case of doping
from the atmosphere is presented. For the calculation of the 2D shape of silicon phase boundaries
and the 3D dopant transport in the melt the models described in [1] and [2] are used, respectively.
Dopant transport in the gas and melt is coupled by the boundary conditions on the melting front and
free melt surface. Results of numerical calculations are compared to the experimental RRV
distribution [4]. An example of the created mesh on puller wall, poly- and monocrystal and two
perpendicular planes in the gas is shown in Fig. 1 and the concentration field in the gas – in Fig. 2.
Figure 1. Fragment of 3D finite volume mesh.
Figure 2. Left: calculated concentration field (in logarithmic scale) in gas in vertical cross-sections. C = 1 at the inlet.
Right: top view of the inductor and the definition of the cross-section planes.
References:
[1] Ratnieks G., PhD thesis, University of Latvia (2007).
[2] Lācis K., PhD thesis, University of Latvia (2010).
[3] Larsen T. L., PhD thesis, Technical University of Denmark (2000).
[4] Rost H.-J., Menzel R., Luedge A., Riemann H., Journal of Crystal Growth, 360 (2012) pp. 43–46.
Impact of growth rate fluctuations on the bulk quality of Czochralski silicon
crystals
Gaspar Guilherme*1, Lanterne Adeline1, Jensen Øyvind2, Lehmann Toni3, Hagen Vegard4, Kildemo Morten4,
Di Sabatino Marisa1, Arnberg Lars1, Øvrelid Eivind5
1
NTNU, Department of Materials Science and Engineering, Alfred Getz vei 2B, Trondheim (Norway)
2
IFE, Instituttveien 18, Kjeller (Norway)
3
Fraunhofer THM, Am St.-Niclas-Schacht 13, Freiberg (Germany)
4
NTNU, Department of Physics, Høgskoleringen 5, Trondheim (Norway)
5
SINTEF Materials and Chemistry, Alfred Getz vei 2B, Trondheim (Norway)
During solar cell processing, striations tend to appear and variation of the electrical properties
and consequently solar cell efficiency are observed [1]. The cause of the growth of striations has
been associated to the melt-temperature fluctuations just below the solidification interface [2].
In the current work, striations formation in Czochralski-grown silicon was studied at different
stages of the growth process with focus on the top of an industrial-scale ingot.
Figure 1 shows the growth interface shape and crystallization instabilities found on a vertical cut on
top of the ingot, as measured by Lateral Photovoltage Scanning (LPS) technique. A typical pull
speed profile used during the growth of the block is also shown in the figure. Even though the pull
speed of the crown has been set as a constant value, growth rate fluctuations are observed. The
influence of the instability on the distribution of interstitial oxygen, defects, minority carrier
lifetime and residual strain have been investigated. Variations of the ingot length and diameter have
been monitored with 1 s time-resolution and the apparent crystal growth rate has been calculated.
Afterwards, the growth rate distribution has been addressed to a 2D transient model of the
Czochralski crystallization process (based on Sisim software) and fluctuations of the vacancy
distribution have been determined and compared with the experimental results. Growth rate
fluctuations have revealed a direct impact on interstitial oxygen, defects and residual strain
distribution. As-grown lifetime has demonstrated to be mainly affected during large growth rate
fluctuations.
Figure 1. LPS image of the ingot top investigated and corresponding input pull speed profile.
References:
[1] Haunschild J., Reis I., Geilker J., Rein S., Physica Status Solidi, 5 (2011) 199-201.
[2] Kanda T., Hourai M., Miki S., Shigematsu T., Tomokage H., Miyano T., Morita H., Shintani A., Journal
of Crystal Growth, 166 (1996) 663-668.
Reduction of carbon contamination during the melting process of Czochralski
silicon crystal growth
Xin Liu*, Bing Gao, Satoshi Nakano and Koichi Kakimoto
Research Institute for Applied Mechanics, Kyushu University,
6-1 Kasuga-Koen, Kasuga, Fukuoka (Japan)
Carbon (C) contamination in Czochralski (CZ) crystal growth of single crystalline silicon (Si) is
detrimental for the minority carrier lifetime, which is one of the critical parameters of wafer for
power device. Effective control of C concentration in the CZ-Si crystal is required for the
production of high performance Si wafer.
Contamination of C in Si crystal mainly originates from carbon monoxide (CO) generation on
the graphite components. And, incorporation of C occurs prior to the growth stage. The reason is
the CO generation starts from the preheating stage, and reaches the maximum in the melting stage
of the CZ-Si crystal growth. To reduce the C contamination effectively, it is essential to control the
C transport from its generation, incorporation and accumulation in the growth. For the reduction of
CO generation, silicon carbide (SiC) coating could be applied to the gas guide above the melt
surface. Enhancement of the argon (Ar) gas flow above the melt could reduce the incorporation rate
of C. And, the accumulation time of C depends on the thermal history of the growth system.
According to these principles, several strategies for reducing C contamination were investigated
numerically in this work.
Transient global simulations of heat and mass transport were conducted for melting process of
CZ-Si crystal growth with different operating parameters. A virtual PID controller for the
temperature was introduced to realize the power control of the heater. Besides the CO generation by
the reaction between graphite and silicon monoxide (SiO), the reaction due to the contact between
quartz crucible and graphite susceptor was also taken into account as another CO source.
Accumulation of C in Si feedstock was predicted for the entire melting process, which consists of
preheating, melting and stabilization stages. Effects of different strategies for C reduction were
analyzed and compared. The SiC coating for the gas guide and the increase of Ar gas flow rate
could suppress the C contamination significantly, as shown in Fig. 1. According to the
accumulation of C, the final C content depends on the growth duration and contamination flux at
the gas/melt interface.
(a)
(b)
Figure 1. Contamination of C in the melted Si. (a) Concentrations of C without coating (left) and with SiC coating (right);
(b) Concentrations of C with Ar gas flow rate of 5 SLPM (left) and 10 SLPM (right).
N-type doping of bulk gallium nitride grown by hydride vapour phase epitaxy
Patrick Hofmann1*, Frank Habel2, Martin Krupinski1, Gunnar Leibiger2, Franziska Christine Beyer3, Stefan
Eichler2, Thomas Mikolajick1,4
1
NaMLab gGmbH, Nöthnitzer Straße 64, D-01187 Dresden, Germany
Freiberger Compound Materials, Am-Junger-Löwe-Schacht 5, D-09599 Freiberg/Sa., Germany
3
Institute of Experimental Physics, TU Bergakademie Freiberg, Leipziger Straße 23, D-09599 Freiberg/Sa., Germany
4
TU Dresden, Institute for Semiconductors and Microsystems, D-01062 Dresden
2
Galliumnitride (GaN), as a representative of wide band gap semiconductors gathers attention
because of its numerous applications in the high power device sector, as well as for optoelectronic
applications [1]. The latter has a crucial necessity for doped material, since the pn-junction needs to
be contacted in order to get light emitting or laser behaviour of the GaN material.
The p-type doping is generally achieved by metalorganic chemical vapour deposition [2] during
deposition of the device itself. Typically n-type GaN is used as base material for the deposition of
the functional layers. Hydride vapour phase epitaxy (HVPE), as one of the industry relevant
methods for growing bulk GaN, offers high crystal quality whilst keeping the unintentional doping
level (UID) low [3]. It therefore qualifies for intentional doping experiments for providing n-type
GaN wafers.
Typically silicon (Si) [4,5] and germanium (Ge) [6] are used as n-type dopants for GaN. Both
occupy the substitutional gallium (Ga) site in the GaN lattice [2]. Si doping leads to tensile stress
generation in the GaN lattice, resulting in fracturing of the GaN crystals [7, 8]. This creates the need
for special growth techniques before doping in order to avoid said fracturing [5].
It is reported, that Ge doping does not show this kind of behaviour [9], hence being the obvious
alternative to Si doping. However, doping during bulk HVPE growth provides other challenges
depending on the dopant source and growth parameters [10].
A detailed characterisation of the silicon doping using dicholorsilane has been carried out and
the influences of the dopant incorporation on the bulk growth were investigated. The bulk GaN:Si
crystals were investigated by confocal Raman- and catodoluminescence measurements to assess the
strain situation of the samples. The crystal quality has been evaluated by X-ray rocking curve
measurements. In dopant intake has been characterised by electrical and optical measurements and
has been verified by mass spectroscopic methods. First results of the Ge doping during bulk HVPE
growth will be discussed in comparison to the bulk Si doping of GaN.
References:
[1] Ehrentraut, D. et al, Technology of Gallium Nitride Crystal Growth 1st ed. (Springer) chapter 1 (2010).
[2] Morkoc, H. Handbook of Nitride Semiconductors and Devices 1st ed. (Wiley-VCH) (2008).
[3] Ehrentraut, D. et al, Technology of Gallium Nitride Crystal Growth 1st ed. (Springer) chapter 9 (2010).
[4] Richter E. et al. Phys. Stat. Sol. (a) 203 (2006) 1658–1662.
[5] Richter E. et al. Electronic Materials 42 (2013) 820–825.
[6] Oshima Y. et al. Journal of Crystal Growth 310 (2010) 3569–3573.
[7] Brunner F. et al. J. Appl. Phys. 112 (2012) 033503–1–033503–5.
[8] Romanov A. E. and Speck J S Appl. Phys. Lett. 83 (2003) 2569–2571.
[9] Dadgar, A. et al. Applied Physics Express, 4 (2011) 011001-1–011001-3.
[10] Yoon M. et al. Japanese Journal of Applied Physics, 44 (2005) 828–832.
Growth of 5 kg-level LBO for ultrashort and ultrahigh power laser
Zhanggui Hu*, Yinchao Yue, Ying Zhao, Heng Tu
Key Laboratory of Functional Crystals and Laser Technology of Chinese Academy of Sciences, Technical Institute of Physics and
Chemistry, CAS, Beijing 100190, China
*Email: [email protected]
The growth of large size and high quality lithium triborate (LiB3O5, LBO) crystal is always the research
hotspot in nonlinear optical crystal field because LBO crystal is widely used in solid-state laser technology. It is
grown by the Top-Seeded Solution Growth method and Li2O-B2O3-MoO3 is currently considered as the most
effective flux system. The LBO crystal grown in conventional methods weighs about 200g and the optical
aperture is generally less than 10mm. With the development of high-energy, high-power laser technology, it is
required that the LBO crystal has a higher quality and larger size. Our group made a breakthrough in largesize LBO crystal growth first in the world.
The first, we designed a large flux crystal growth equipment to grow LBO crystals. The second, we
adopted a new solute transport technique as well as a new flux system. The third, in order to process the large
crystals we grew into larger diameter devices, we proposed a new method for the LBO crystal growth: near
phase-matching angle direction growth. In 2007, we obtained 1 kg-scale LBO (1116.8g) crystal for the first
time. In 2013, the largest LBO single crystal reported in the world with the size of 285×160×110 mm3 and the
weight of 4798g was successfully grown in 180 days by us. In 2014, based on the the first 100×100×10 mm3
LBO device in the world we provided, a high power 32.0fs and 1.0 PW laser has been achieved through
OPCPA, which represents the highest reported laser output in the world.
In the meanwhile, we have achieved 510 W green laser using 15×5×100 mm3 LBO device, and may achieve
KW power output soon. LBO device with the aperture of 150×150×10 mm3 has been fabricated for ongoing
higher power laser experiment. Moreover, in the near future, LBO crystal with aperture larger than 250 mm will
play an active role in the progress of large-aperture, high-energy, high-power laser techniques especially for
OPCPA system, ICF, and fusion energy.
as grown LBO crystal: 240mm×160mm×110mm
POSTER
S04-P01
Bulk growth of optical quality inverted Solubility Li2SO4.H2O single crystals by
the improved Sankaranarayanan -Ramasamy method
A. Silambarasan, P. Rajesh*, P. Ramasamy
Research Centre, Department of Physics, SSN College of Engineering, Kalavakkam-603110, Tamilnadu, India
*email: [email protected], [email protected]
In the trend for the development of single crystals for second harmonic generation (SHG),
Lithium Sulfate Monohydrate (LSMH) single crystal will undoubtedly attract more attention
because of its good nonlinear optical coefficient and broad transparency range. The inverted
solubility, pyroelectric behavior and higher density of LSMH makes difficult to grow as good
quality bulk size single crystals. Also, the grown LSMH crystals have some defects and the
transparency was poor due to spurious nucleation at the top region of the solution. In this work,
significant modifications in the uniaxial solution-crystallization Sankaranarayanan - Ramasamy
(SR) method was made in order to avoid such difficulties. Notably, bulk size LSMH single crystal
was grown in short period with higher growth rate and excellent optical qualities than previous
reports. The LSMH crystal grown by this method fulfilled all the requirements, such as a second
harmonic response and splendid crystal characteristics including large crystal size with desired
facets, higher laser damage stability, superior optical quality, wide transparency range, and
controllable crystal thickness, which are in general extremely difficult to achieve simultaneously in
single system. Therefore, the LSMH crystal could emerge as a potential candidate for applications
in laser photonics and optoelectronic devices
.
Figure .(a) Conventional grown LSMH (b) SR grown LSMH (c) SR grown LSMH with scale
S04-P04
TSFZ-growth, magnetism and ac conductivity of LiMn1-xFexPO4 single crystals
Christoph Neef*1, Hubert Wadepohl2, Hans-Peter Meyer3, Rüdiger Klingeler1
1
Kirchhoff Institut für Physik, Universität Heidelberg, D-69120 Heidelberg (Germany)
Anorganisch-Chemisches Institut, Universität Heidelberg, D-69120 Heidelberg (Germany)
3
Institut für Geowissenschaften, Universität Heidelberg, D-69120 Heidelberg (Germany)
2
Olivine-structured materials LiMPO4 (M = Mn, Fe, Co, Ni) are one of the promising present and
next generation cathode materials for lithium-ion batteries. In order to understand and to simulate
the relevant processes associated with Li-(de)intercalation, information on the anisotropic Litransport properties and on structural phase changes during intercalation is crucial. In addition to
these partially application driven research demands, strong magneto-electric effects, magnetic
frustration and unusual ferrotoroidal ordering phenomena raise more fundamental questions in this
materials class as well.
In the present work, mm-sized single-crystals of the series LiMn1-xFexPO4 (x=0, 0.3, 0.5, 1)
were grown using the optical floating zone technique. Li2O volatilization during the melting
procedure, which is typical for Li containing oxides, was strongly reduced by increasing the
ambient pressure to 30 bar of purified Ar. The resulting samples are characterized by EDX and
single crystal XRD showing a successful growth and the solid solution behavior between the end
members LiMnPO4 and LiFePO4. SQUID magnetometry and thermal expansion studies at low
temperatures imply antiferromagnetic order with the Neel temperature continuously shifting upon
Fe doping from 33 K for LiMnPO4 to 50 K for LiFePO4.
The composition dependent bulk conductivities of the series, which are of particular interest for
application as battery material, are studied using ac impedance measurements. The ac conductivity
strongly increases for Fe contents above x = 0.5 while it is low for the Mn rich compounds with x ≤
0.3. Independent of the composition, there is an anisotropy in the ac conductivity between the
crystallographic main axes amounting to about one order of magnitude, favoring the b-axis.
Figure 1. left: Oriented and cut crystal with compostion LiMn0.7Fe0.3PO4; right: Crystal structure
according to single crystal XRD. PO4 tetrahedra in green, MO6 octahedra (M=Mn, Fe) in blue.
S04-P06
Czochralski growth of bulk Li2MoO4 crystals for the scintillating bolometers
used in the rare events searches
Matias Velázquez*1, Pierre de Marcillac2, Andrea Giuliani2, Philippe Veber1, Dominique Denux1, Rodolphe
Decourt1, Oudomsack Viraphong1
1
Centre de Sciences Nucléaires et de Sciences de la Matière, CSNSM, UMR 8609, CNRS-Université d’Orsay, Bât. 108,
91405 Orsay Campus (France)
2
The search for the neutrino mass and the direct detection of the dark matter of our universe
stand among the most exciting science drivers of today’s astroparticle physics. Crucial experiments
in these domains require detecting extremely rare events, such as neutrinoless double beta decays
(0-DBD) [1], or nuclear recoils induced by massive particles interacting weakly (WIMPS) with
baryonic matter, considered as viable candidates to be the quantum components of the dark matter
halo of our galaxy [2]. The DBD gives unique information about the neutrinos properties, their
absolute mass scale, mass hierarchy and their nature. In addition, the direct detection of WIMPs
would solve the recurring enigma on the very nature of dark matter, which is expected to constitute
26.8% of our universe’s content. Another rare event search with high discovery potential is the
detection and spectroscopy of fast and extremely rare neutrons, which would help understanding the
ultimate background of the dark matter direct detection underground sites. In all these cases,
because of their high energy resolution and low energy threshold, heat-scintillation cryogenic
bolometers (HSCBs) turn out to be very sensitive tools to carry out this exploratory research.
HSCBs work at very low temperature (≤25 mK) and measure an energy release in a single crystal
by means of both weak heat and light pulses resulting from the same nuclear event. HSCBs
containing Mo as a constituent element have a tremendous potential in fundamental neutrino
physics, especially if the detectors can be made with an extremely low content of radioactive
impurities. Indeed, the isotope 100Mo, present at the 9.7% level in natural molybdenum, is an
excellent candidate for a rare nuclear process known as 0-DBD. If observed, this decay would
prove that neutrino is a Majorana particle, i.e. a fermion equal to its own anti-fermion or, in other
words: a new type of matter. The implications of this fact would be long-reaching in fundamental
physics, ranging from the understanding of the origin of the elementary particle masses to the
explanation of the dominance of matter over anti-matter in the Universe. The core of HSCBs is
made of radiopure bulk single crystals constituted as much as possible of nuclei that exhibit high
capture cross sections of the relevant particles or that are themselves the source of the rare event to
be detected. It just so happens that Li2MoO4 is a strategic crystal, because of the possibility to
enrich it with 6Li, 7Li or 100Mo isotopes, the corollary absence of long-lived radioactive isotopes, its
remarkable 232Th and 238U chains radiopurity, its sufficient light yield at low temperatures, its low
and congruent melting point. In this talk, we will present our latest efforts to obtain bulk Li2MoO4
single crystals, of mass several hundred grams, by the seeded Czochralski method and discuss their
growth conditions. Their characterization in terms of radiopurity levels (especially 40K), chemical
purity and segregation, optical transmission, specific heat, differential scanning calorimetry and
thermal expansion will also be reviewed.
References:
[1] M. Tenconi et al., Physics Procedia, 61 (2015) 782-786.
[2] G. Angloher et al., Physics of the Dark Universe, 3 (2014) 41-74.
S04-P07
Czochralski growth and physical properties characterizations of 6Li- and 10Benriched crystals for heat-scintillation cryogenic bolometers used in the rare
events searches
Matias Velázquez*1, Rekia Belhoucif1,2, Yannick Petit1, Olivier Plantevin3, Benoît Glorieux1,
Oudomsack Viraphong1, Pierre de Marcillac3, Noël Coron4, Lidia Torres4, Philippe Veber1,
Rodolphe Decourt1
1
2
Faculté de Physique, Laboratoire d’Électronique Quantique, BP 32 El alia, 16111 Bab Ezzouar, Alger (Algeria)
3
4
IAS, Bâts. 120-121, UMR 8617 Université Paris-Sud 11/CNRS, 91405 Orsay Campus (France)
Heat-scintillation cryogenic bolometers (HSCBs) are low threshold, high sensitivity, double
readout detectors that measure simultaneously the heat and the light generated by a particle inside a
crystal [1]. These detectors are being developed for dark matter direct detection [2], neutrinoless
double beta decays, fast neutron spectroscopy, extremely long radioactive decays, among other rare
events. A bolometer consists of a crystal absorber strongly coupled to a thermometer, both weakly
coupled to a heat sink maintained at 10-30 mK. In this context, we are attempting to grow crystals
with diameters of several centimeters and thicknesses several times the thermal neutron mean free
path in 6Li-based crystals and the range of neutron capture induced particles in crystals made of 6Li
or 10B, these mean free paths typically being 6 m for ’s and 34 m for tritiums in lithium borates.
Since the 6Li and 10B isotopes, as well as several Gd isotopes, exhibit high neutron capture crosssections (10B-n4×6Li-n~6.10-24 cm2 @ 10 keV) [3], it soon turned out that crystals of the
Li6Gd(BO3)3-type would constitute ideal candidates for both tailoring HSCBs with high light yields
over a wide neutron energy range and adapting them to powerful light detectors working at low
temperature and available from UV to X-ray spectral ranges. Moreover, in contrast with the 6LiF
bulk crystals that we had already obtained, 6Li6(Eu,Gd)(10BO3)3 crystals are much less likely to
exhibit thermoluminescence effects detrimental to HSCB applications [4]. In this poster
presentation, we report on the crystal growth by combined Czochralski and Kyropoulos methods,
initiated on specifically oriented seeds, of centimeter-sized 6Li6Eu(10BO3)3 and Li6(Eu,Gd)(BO3)3
single crystals with an heretofore unexplored concentration range for HSCBs operation. Their
chemical purity, Gd depletion profiles and radiopurity levels are detailed. The most relevant
physical properties, such as thermal conductivity, thermal expansion, mechanical hardness,
polarized visible absorption and emission, specific heat combined with magnetic susceptibility and
scintillation are discussed.
References:
[1] H. Kraus et al., 2010, PoS(IDM2010) 109.
[2] G. Angloher et al., Physics of the Dark Universe, 3 (2014) 41-74.
[3] G. F. Knoll, In Radiation detection and measurement, 4th ed., J. Wiley & Sons (Ed.), 2010, chp.
14-15.
[4] M. Martinez et al., J. Phys. : Conf. Ser., 2012, 375, 012025/1-4.
S04-P09
Influence of melt convection on the aggregation of inclusion in massive sapphire
and garnet crystals for growing by HDC method
Nizhankovskyi S.V.*1, Tan’ko A.V. 1, Sidelnikova N.S. 1, Naydenov S.V. 1, Janovsky V.V. 1
1
Institute for Single Crystals, State Scientific Institution “Institute for Single Crystals” of National Academy of Sciences
of Ukraine, Lenin 60, Ave, 61001, Kharkiv, Ukraine
Sapphire and rare-earth garnet crystals possess a unique combination of physical and chemical
properties; therefore they are widely used in optics, optoelectronics and laser technique. One of the
main methods to obtain such crystals is a horizontal directed crystallization (HDC) method that
allows growing crystals with different crystallographic orientation in the form of large size plates
with a high homogeneity of the functional characteristics [1]. During massive crystals growing
(plate thickness ≥ 30 mm) some "longitudinal" aggregation of inclusions (impurity phases,
bubbles), distributed along the direction of crystal growth (Fig. 1 a), could appear. Such aggregation
has a domelike shape with rounding to the lateral sides of the crystal, which allows us to suggest
that defects appear at some specific convection conditions in the melt (Fig. 1 b) [2].
With numerical simulation we analyzed convection in sapphire (Al2O3) and garnet (YAG) melt
and the thickness of the diffusion layer in the vicinity of the crystallization front as a function of
melt overheat, geometrical parameters of the melt zone (height h and length L) and the
crystallization front shape. It was established that the longitudinal aggregation generation is caused
essentially by a diffusion layer local thickening in the contact region of two flows (thermocapillary
and buoyancy-driven flow) (Fig. 1c). Convective flows capture bubbles and impurities and transfer
them to this contact region, where they are accumulated and defect aggregation is formed. It is
shown that choice of optimal temperature growth conditions and geometrical parameters of the melt
zone allows to grow massive (up to h > 50 mm) sapphire and garnet crystals by HDC method
without defect aggregation [3].
Figure 1. Longitudinal (a) and cross (b) section of sapphire crystal containing inclusions; the two-
vortex motion of melts and diffusion layer in the vicinity of the crystallization front (c)
References:
[1] S.V. Nizhankovskii, N.S. Sidel`nikova, V.V. Baranov, Physics of the Solid State, V.57, (2015), pp.
781-786.
[2] Dan’ko A., Nizhankovskiy S. V., Puzikov V. M., Crystallography Reports, V.53 (2008), pp. 1272–1275.
[3] Nizhankovskyi S., Tan’ko A., Sidelnikova N., Adonkin G. Cryst. Res. Technol. 50, No. 3, 223-229
(2015).
S04-P10
Range of the temperature gradients and the growth rate values in the growth of
CZT crystals from the melt
Repiso Eva1, Corrochano Álvaro1, Rubio Sandra1, Plaza Jose Luis1, Tsybrii Zinoviia2, Vuichyk
Mykola2,Dieguez Ernesto*1
1
Depart: Physics of Materials, Universidad Autónoma de Madrid (UAM), Madrid (Spain)
2
Institute of Semiconductor Physics (ISP), Kiev, (Ukraine)
CdZnTe bulk crystals have been broadly employed in room temperature X-ray and gamma ray
semiconductor detector applications due to their attractive physical-chemical material properties, in
particular the high energy detection as an important parameter in medical imaging and homeland
security applications. The presence of secondary phases, Te inclusions, dislocations, Cd vacancies,
polycrystallinity, etc. are common facts that may cause the detector degradation, but that it can be
reduced by adequate growth conditions. In fact, although it´s possible to build CdZnTe compact
detectors for their use in the above mentioned applications, a tight control of a number of crystal
growth parameters is needed to obtain high quality single crystal CdZnTe materials.
The most often methods for growing large CZT crystals from the melt are Bridgman and
Vertical Gradient Freeze techniques. Although they are both well-developed techniques, the lack of
complete information about the growth parameters is a general fact in the publications on this field.
For this reason, in this work we plan to validate the two most important growth parameters such as
the growth rate (V) and the temperature gradients (G) in the solid (s) and in the liquid (l) in view of
the heat balance equation in the solid liquid interface (SLI), taking into account known values for
the thermal conductivities of the solid and the liquid (Ks, Kl).
The range of the Gs and Gl versus V was examined by analyzing both experimental and
simulated data obtained in the VGF technique. The Gs/V versus Gl/V representation gives a straight
line where the slope is given by the ratio of the thermal conductivities Kl/Ks, being the range for an
adequate V crystal growth value deduced from this figure. Moreover, the dependence of G in the
solid and in the liquid on the V value shows that Gl has a negative dependence with V, while Gs
linearly increases with the growth rate, giving the ratio of the Gs and Gl values the same as Kl/Ks
when the growth rate is zero. Furthermore, the dependence of the product of thermal conductivities
and the thermal gradient in the solid and in the liquid (KsGs, KlGl) on the growth rate shows that
when V increases, Gl decreases and Gs increases to offset the product of LV. A complete view of
the dependence of G on V using own and published experimental data, together with simulation
results will be analyzed in this paper.
References:
[1]A. Natsume, N. Inoue, K. Tanahashi, A.Mori, Journal of Crystal Growth, 225 (2001) 221-224.
[2] H. Bensalah, J.L. Plaza, J. Crocco, Q.Zheng, V. Carcelén, A. Bensouici, E. Diéguez, Applied Surface
Science, 257 (2011) 4633-4636
S04-P11
Growth and Laser performance of a new IR NLO crystal BaGa4Se7
Yao Jiyong*1, Yang Feng1, Wu Yicheng1; Xu Zuyan1
1
Technical Institute of Physics and Chemistry, CAS, , Beijing (China)
BaGa4Se7 is a new IR NLO crystal recently discovered by us. It possesses a number of
advantages including large NLO coefficients（d11=24pm/V), high transparency in the wide range
of 1-14 µm, high laser damage threshold, and large birefringence. High quality Φ30mm×70mm
crystals have been obtained. Preliminary optical parametric experiments have achieved high
efficiency and high peak power “3-11µm” laser output, and optical rectification has also realized
narrow band 2Thz output. These results indicate BaGa4Se7 is a very promising new IR NLO crystal.
Figure 1. Φ30mm×70mm BaGa4Se7 crystal
Figure 2. The tuning performance in 3–5μm
THz Signal in Frequency Domain
90.0p
Amplitude (A.U.)
f=1.936THz
60.0p
30.0p
0.0
0.5
1.0
1.5
2.0
2.5
Frequency (THz)
Figure 3. The tuning performance in 6.4–11μm
Figure 4. Narrow band Thz output
S04-P12
Growth from the melt, structure and properties of the crystals of
(ZrO2)1-x(Sc2O3)x solid solutions
Borik Mikhail1, Bredikhin Sergey2, Kulebyakin Alexey*1, Kuritsyna Irina2, Lomonova Elena1,
Milovich Filipp3, Myzina Valentina1, Osiko Vyacheslav1, Panov Vitaliy1, Seryakov Sergey3,
Tabachkova Nataliya3
1
A.M. Prokhorov General Physics Institute RAS, Vavilov Str., 38, 119991, Moscow (Russia)
Institute of Solid State Physics RAS, Institutskaya str., 2, 142432, Chernogolovka (Russia)
3
National University of Science and Technology «MISIS», Leninsky pr., 4, 119049, Moscow (Russia)
2
Single crystals of (ZrO2)1-x(Sc2O3)x solid solutions were grown using directional melt
crystallization in a water-cooled copper crucible diameter of 130 mm. Crystal growth was carried
out on the "Kristall-407" (frequency - 5.28 MHz, the maximum output power of 60 kW). The
weight of the material that was loaded into the cold container was approximately 6 kg. Directional
melt crystallization was conducted by moving the crucible with the melt relative to the inductor at a
rate of 10 mm/h. Were grown crystals of (ZrO2)1-x(Sc2O3)x solid solutions with x = 0.035, 0.06,
0.09, 0.11. The crystals have a columnar shape; typical crystal size is 20-30 mm - length and 10-15
mm - cross section. For crystals containing 3.5 and 6 mol% Sc2O3 is characterized by the presence
of cracks in the crystal after the growth. Analysis of the scandium oxide distribution on the length
of the crystal showed that the composition of all the samples is homogeneous and Sc2O3
concentration practically corresponds to its content in the starting material. All the studied samples
show a low tendency to decrease of the concentration of Sc2O3 along the crystal, which indicates
that the effective distribution coefficient Sc2O3 slightly greater than 1.
Phase composition and structure of the crystals studied by x-ray diffraction (XRD), Raman
spectroscopy and transmission electron microscopy (TEM). It is found that the crystals have a
different phase composition depending on the concentration of scandium oxide. The samples
containing 3.5 mol% Sc2O3 is characterized by the presence of the monoclinic and tetragonal
phases. The samples with 6 mol% scandium oxide have a tetragonal structure. In the crystals with
9 mol% Sc2O3 concentration presented tetragonal phase with a mixture of rhombohedral phase. The
specimens containing 11 mol% Sc2O3 consist only of rhombohedral phase. The identity of the phase
composition of crystals during their studies by the above methods indicates the absence of phase
transitions in these crystals induced by mechanical stress. It is important to note that all samples are
not detected the presence of the cubic phase. For all investigated crystals is characterized by
twinned structures of different types and sizes depending on the composition. Physico-chemical
properties of the crystals, such as density, microhardness and crack resistance were measured. It is
shown that the crystals have a high hardness, but low crack resistance. The data on the measurement
of the temperature dependence of the electrical conductivity of crystals containing 6 and 9 mol%
Sc2O3 are presented.
As a result of our preliminary experiments we were obtained large, homogeneous, optically
transparent single crystals in the system ZrO2-Sc2O3-Y2O3. At the present time we study properties
of the crystals.
The work was supported by research grant № 14-29-04081 of the Russian foundation for basic
research (RFBR) ofi-m.
S04-P13
Bulk crystals of L-Histidinium dihydrogen phosphate orthophosphoric acid
grown by Sankaranarayanan - Ramasamy method
Reena Ittyachan a , A.Arunkumar b
a
Department of Physics, Sacred Heart College, Chalakudy, Kerala- 680307, India
SSN Research Center, SSN college of Engineering, Kalavakkam- 603 110, India
b
Transparent L-Histidinium dihydrogen phosphate orthophosphoric acid (LHDP) crystal of
length 80 mm long and 20 mm diameter has been grown from aqueous solution along c-axis using
Sankaranarayanan - Ramasamy method. The unit cell parameters were confirmed by single crystal
X-ray diffraction analysis and it belongs to orthorhombic system. The crystalline perfection of
grown crystals was analyzed by High-resolution X-ray diffraction. The UV-vis-NIR spectrum
showed that the grown crystal is transparent in the entire visible region. . The lower optical cut-off
wavelength for this crystal was observed at 240 nm. Fluorescence studies were carried out in range
of 200 – 700 nm. Thermogravimetric and differential thermal analysis was carried out to determine
the thermal property of the grown crystal. The mechanical property of the grown crystal was studied
by Vickers Microhardness measurement. The third order nonlinear refractive index (n2), nonlinear
absorption coefficient (β) and susceptibility (χ(3)) were calculated by Z-scan studies using Nd:
YAG laser as a source. It is found that the AAP molecule is a potential candidate for optical
limiting applications. The laser damage threshold was measured using Q-switched Nd: YAG laser
(1064 nm).
Photograph of SR grown ammonium acid phthalate single crystal.
S04-P15
Control of sapphire crystal morphology grown in a Kyropoulos furnace
Gourav Sen*1, Guillaume Alombert-Goget2, Cyril Pezzani3,Nicolas Barthalay3, Thierry Duffar1,
Kheirreddine Lebbou2, Bruno Delagenière4
1
SIMAP-EPM, UMR 5266 CNRS, 38402 Saint Martin d’Hères (France)
Institut Lumière Matière, Université Lyon 1-UMR 5306 CNRS, 6922 Villeurbanne (France)
3
RSA le rubis SA, BP 16, 38560 Jarrie/Grenoble (France)
4
Cyberstar, Parc Sud Galaxie - 1, rue des Tropiques - 38130 ECHIROLLES (France)
*[email protected]
2
The Kyropoulos method is used to grow large sized titanium-doped sapphire single crystals for
power laser applications. However these crystals possess some huge macroscopic defects like
bubbles and haze which render a large bulk of the crystal unworthy for use. The crystal shape
evolution during the growth process influences the presence of these defects and hence an effort
was made to study the crystal shapes as an effect of varying growth parameters. A comparison was
made on various grown crystals to establish the relationship between the morphological defects and
the growth parameters. An ideal growth process has been defined with the growth parameters for
different stages of evolution of the crystal. An automated method of growth process control was
developed to maintain those parameters and thus obtain crystals of a superior quality.
A)
B)
Figure 1.Titanium doped Sapphire ingots obtained by Kyropoulos method; A) Ingot obtained by
manual control of growth parameters, B) Ingot obtained by automatic control
S04-P16
Influence of Growth Conditions in Interface shape and Stability in Antimony
doped Germanium Single Crystals using VB, AHP, and AVC Techniques
Sheikhi Aidin*1, Yousefi. L Pouya1, Balikci Ercan1
1
Bogazici University,Department of Mechanical Engineering 34340 Bebek, Istanbul (Turkey)
Single crystal growth of antimony doped germanium is investigated by Vertical Bridgman (VB)
[1], Axial Heat Processing (AHP) [2], and Axial Vibrational Control (AVC) [3] techniques. In order
to achieve homogeneous crystals, stability of a planar interface should be maintained during the
growth. To this end, effective parameters on morphological stability such as melt height,
temperature gradient, and growth rate should be studied carefully. AHP method provides accurate
data for such investigation. This method is similar to VB method. The crystallization takes place in
a vertical cylindrical crucible which is surrounded by 4-zone furnace that establishes axial
temperature gradient along the crucible. In order to reduce the melt height and effects of natural
convection, a submerged baffle is used inside the crucible. Additionally, in the AVC method, the
axially vibrating submerged baffle can modify the heat and mass transfer ahead of the growth
interface in a desired way by optimizing the amplitude and frequency of the vibration and distance
of the baffle from the interface. Hence, the vibrating baffle mixes the melt region under the baffle
that can promote a planar interface, reduce radial temperature gradient, and homogenize radial
solute distribution.
In order to investigate the interface shape and solute segregation, the grown crystals are axially
cut into two halves. Then, the surface of one half is ground, polished, and electro-etched to visualize
striation lines which show position and shape of the interface during the growth. Also, radial and
axial solute concentration in each crystal is measured by the four-point probe technique on the
polished surface. Moreover, morphological stability of the grown crystals in different techniques is
compared to each other. Results show that the stability is enhanced for the crystal grown with the
AVC technique by applying 2 mm amplitude and 0.25 hertz frequency to the vibrating baffle. It has
been observed that solute segregation is reduced, interface shape becomes more planar, and the
single crystal length is increased up to 180 percent in comparison to the crystal grown with the VB
method.
References:
[1] P. W. Bridgman, “Various Physical Properties of Rubidium and Cesium and the Resistance of Potassium
Under Pressure”, Proceedings of the American Academy of Arts and Sciences, 60 (1925) 385.
[2] E. Balikci, A. Deal, R. Abbaschian, et al, Crystal Growth & Design, vol. 4, No 2, (2004), pp. 377-381.
[3] I. K. Avetisov, A. Y. Melkov, A.Y. Zinovev, E. Zharikov, “Growth of nonstoichiometric pbte crystals by
the vertical Bridgman method using the axial-vibration control technique”, Crystallography Reports, 50 (1)
(2005) S124-S129.
The study is supported by TÜBİTAK, TURKEY, grant no 212M030.
S04-P19
VGF growth of GaAs doped with 12C, 16O and 18O for the study of midinfrared vibrational modes
Christiane Frank-Rotsch1, Alexander Glacki2, Hans Christian Alt3, Hans-Edwin E. Wagner3
1
Leibniz Institute for Crystal Growth, Max-Born-Str. 2, 12489 Berlin (Germany)
2
present address: Schott AG, Hattenbergstr.10, 55122 Mainz (Germany)
3
University of Applied Sciences, Lothstr. 34, 80335 Munich (Germany)
Various growth experiments were conducted for an aimed doping of bulk GaAs with carbon 12C,
and oxygen isotopes 16O and 18O. Aim was to identify the origin of the sharp absorption band at
2060 cm-1 in annealed GaAs crystals, which was hitherto attributed to the local vibrational mode of
a complex containing both C and O [1].
4’’-GaAs crystals with weight of about 1 kg were grown by the Vertical Gradient Freeze technique
under the influence of traveling magnetic fields [2] for the improvement of melt stirring,
stabilization of the growth process, and the enhancement of the dopant incorporation [3]. High
carbon concentrations were achieved by adding roughened graphite plates to the melt. Oxygen was
introduced either by adding various quantities of boron oxide or/and GaOOH to the crucible (see
Fig. 1). The GaOOH was synthesized using either conventional H216O or H218O and Ga. The B2O3
was either dry with 200 ppm water content or wetted by H216O and H218O in different volume ratios.
Low-temperature Fourier transform infrared absorption measurements of a GaAs sample with a
total oxygen concentration of 3.4x1015 cm-3 and an enrichment of the 18O isotope (16O:18O~30:1)
revealed that the satellite band of 2060 cm-1 at 2050 cm-1, which was previously attributed to the
18
O isotope, was not enhanced in comparison with spectra containing the natural oxygen isotope
ratio (500:1) [4]. This ruled out any defect model involving oxygen atoms. The origin of the 2060
cm-1 mode was subsequently identified as a complex of the composition CN2 by implantation of the
isotopes 14N and 15N into standard semi insulating GaAs wafers.
Figure 1: Crucible equipment for growth experiments for an aimed doping with 12C, 16O and 18O: a) 18O
was introduced by adding GaOOH b) 18O was introduced by wetting the B2O3 with H218O before growth
References:
[1] W. Ulrici and M. Jurisch, Phys. Status Solidi B 242, 2433 (2005)
[2] Frank-Rotsch et al., J. Crystal Growth 401, 702-707 (2014)
[3] Glacki et al., J. Crystal Growth 397, 6-12 (2014)
[4] H. Ch. Alt et al., submitted to Phys. Status Solidi B (2015)
S04-P20
The search for novel solvents for the single crystal growth of germanate phases
by the flux method
Ivanov Vladimir
*1
, Marychev Mikhail 1, Andreev Pavel 1, Koseva Iovka 2, Tzvetkov Peter 2, Nikolov Velin 2
1
2
N.I. Lobachevsky State University of Nizhni Novgorod, Nizhni Novgorod (Russia)
Bulgarian Academy of Science, Institute of General and Inorganic Chemistry, Sofia (Bulgaria)
A series of alkali-borate (Na2O·B2O3, Na2O·1.5B2O3, Na2O·2B2O3 and Li2O·B2O3), and a series
of alkali-molybdate (Na2O·1.5MoO3, Na2O·2MoO3 and Li2O·MoO3) solvents were studied with a
view to find out the suitable conditions for growing single crystals from germanate phases by the
flux method. The ternary systems solvent-CaO-GeO2 were investigated and crystallization
temperature and crystalized phase were determined. As a main result the concentration and
temperature regions of crystallization of calcium germanates (Ca5Ge3O11, CaGeO3) and of some
alkali germanates (Li2GeO3, Li2CaGeO4, Na2CaGe6O14) were experimentally determined for a first
time. The conditions found for Ca2GeO4 growth are significantly more favorable than those known
so far.
The results of the performed study give a basis for producing single crystals by the flux method
from a series of germanate compounds with various application areas. Cr4+-doped single crystals of
Ca2GeO4, which are among the best prospective materials for solid state lasers emitting in the 1.11.6 μm range, can be successfully grown from a Na2O·B2O3 solvent, as well as from a Li2O·B2O3
solvent [1]. Although the solutions contain high amounts of CaO and GeO2, there is no noticeable
evaporation and the viscosity is of the order of 60 cP. The initial crystallization temperature that
could be used is about 1150oC which is considerably lower than that with the solvent CaF2 used so
far (above 1350oC) [2]. The problems encountered upon using CaCl2 as a solvent are also
eliminated (evaporation, hygroscopicity) [2, 3].
The same solvents can be used for growing single crystals of Ca5Ge3O11 (another potential laser
matrix) and single crystals of CaGeO3 with crystallization temperatures of about 1050oC - 1100oC
[1]. The recommended conditions for growing lithium germanates (Li2GeO3 and Li2CaGeO4) from
a Li2O·MoO3 solvent are also given. The crystallization regions of the two phases are rather broad
and the crystallization temperatures are in the range of 950-1050oC.
Special attention was paid to the possibility of growing single crystals from (CaLi)2GeO4 solid
solutions from the system Li2O·MoO3 – CaO – GeO2. The preserved olivine structure of Ca2GeO4
with partial substitution of Ca for Li is a potentiality for alteration of the optical properties of
Ca2GeO4.
The research is supported by a grant (agreement of August 27, 2013 № 02.В.49.21.0003
between the Ministry of Education and Science of the Russian Federation and N.I. Lobachevsky
State University of Nizhni Novgorod).
References:
[1] Ivanov V.A., Marychev M.O., Andreev P.V., Koseva I., Tzvetkov P., Nikolov V., J Cryst. Growth.
Available online 9 May 2015. DOI: 10.1016/j.jcrysgro.2015.04.042
[2] Bykov A.B, Petricevic V., Steiner J., Yao Di, Isaacs L.L., Kokta M.R., Alfano R.R., J Cryst. Growth V.
211 Issues 1–4 (2000) 295-301. DOI: 10.1016/S0022-0248(99)00770-8
[3] Nishi F., Takéuchi Y., Acta Crystallogr. C V. 40 Part 5 (1984) 730-733.
DOI: 10.1107/S0108270184005515
S04-P21
The reduction of basal plane dislocations by modifying thermal conductivity of
the crucible during PVT growth of 4H-SiC single crystals
Kazuma Miyazaki*1, Bing Gao2, Satoshi Nakano2, Koichi Kakimoto1, 2
1
Dept. Aeronautics and Astronautics, 744, Motooka, Nishi-ku, Fukuoka 819-0395 (Japan)
2
RIAM, Kyushu University, 6-1, Kasuga-koen, Kasuga, Fukuoka 816-8580 (Japan)
SiC is expected as the power device material which replaces Si and makes energy saving achieved. The
physical vapor transport (PVT) method is the most practical and commonly used method to grow bulk SiC
crystals. However, reduction of dislocation density by the PVT growth is more difficult than other growth
methods of the SiC single crystals. In this study, we performed a numerical analysis of the reduction of basal
plane dislocation (BPD) density in SiC single crystals. In this analysis, we modified thermal conductivity of
a part of the graphite crucible constituting a crystal growth furnace and examined variation of the BPD
density.In our numerical analysis, we substitute the resolved shear stress into the Alexander-Haasen model
proposed by Gao et al. to obtain the BPDs [1]. 4H-SiC crystals have three primary slip directions in the (0001)
basal plane, and the rate of the mobile dislocation density in slip direction
is given by
(1)
where the subscript m denotes the mobile dislocation,
is the stress exponential factor, N is the dislocation
is the effective stress for dislocation multiplication, and
is
density, K is the multiplication constant,
the slip velocity of dislocation. In additin to this equation,
fluctuates by
, and
is decided by the
resolved shear stress in primary slip direction
[2]. Thus, the BPD density depends on
, and it
finally greatly depends on the stress
[3]. Thermal conductivity
of the graphite crucible that we set is
is the temperature):
as follows (where
(2)
Figures 1 and 2 show distributions of BPD and temperature with the two different thermal
conductivities at the time of the growth end. We set the heater power and pressure in a furnace kept
constant as 18kW and 1 Torr, respectively. Figure 1 shows that lower BPD could be resulted in the
lower thermal conductivity of the material. This is due to the result of lower radial heat flux
(
) and the gradient of the flux (
Figure 1. Comparison of the BPD density
(left half: , right half: )
) shown in Fig. 2 [2].
Figure 2. Comparison of the temperature
distribution (left half: , right half: )
References:
[1] B. Gao, K. Kakimoto, J. Cryst. Growth, 386 (2014) 215
[2] B. Gao, K. Kakimoto, Cryst. Growth Des. , 14 (2014) 1272
[3] K. Bottcher, K. Andrew Cliffe, J. Cryst. Growth, 303 (2007) 310
S04-P22
Dosimetric properties of luminescence crystals grown by Micro-Pulling Down
Method
B. Marczewska, P. Bilski, W. Gieszczyk, M. Kłosowski, A. Twardak, D. Wróbel
Institute of Nuclear Physics PAN, ul. Radzikowskiego 152, 31-342 Kraków, Poland
e-mail:[email protected]
Ionizing radiation is more and more widely used in many areas of life such as medicine,
industry and science. Individual radiation protection of workers as well as environmental
monitoring are most often conducted by passive detectors based on luminescence materials. Besides
LiF which is commonly applied in thermoluminescence (TL) method of dose measurement and
Al2O3 used in optically stimulated luminescence (OSL), there is still a need for seeking the new
luminophors. The most promising new materials appear to be lithium aluminate (LiAlO2) and
lithium magnesium phosphate doped with terbium and boron (LiMgPO4:Tb,B). Both of them are
especially interesting due to the presence of Li-6, which gives them the potential ability to be
applied as dosimeters in neutron fields.
The aim of the work is to investigate the dosimetric properties of LiAlO2 and LiMgPO4 crystals
as OSL dosimeters in regard to their sensitivity to the radiation, repeatability of the OSL signal and
dose response. Crystals were grown by Micro-Pulling Down method at IFJ PAN in Kraków.
Crystals were pulled down from iridium crucibles in the argon atmosphere with different growth
rates from 0.1 to 20 mm/min. The crystals in the form of rods with the diameter of about 2 mm and
the length of 10 cm were cut to smaller slices. The luminescence of the samples was investigated
with OSL method in an automated TL/OSL reader (model DA-20) produced by Risoe National
Laboratory, Denmark. OSL measurements were done using blue diodes (470 nm ± 30 nm) for
stimulation. The readouts were performed using an U340 optical filter transmitting 250-400 nm
light wavelength. The samples were irradiated with beta rays from 90Sr/90Y and alpha particles from
241
Am sources built-in TL/OSL reader.
The sensitivity of the LiAlO2 and LiMgPO4 crystals to the ionizing radiation is very high and
can even exceed the sensitivity of commercially available Al2O3:C detectors. The crystals show
good dose response which is linear in the dose range from 0.01 mGy to 1 kGy for irradiation with
beta rays. The dependence of dosimetric properties of LiAlO2 and LiMgPO4 crystals on growth
conditions, feed material composition and dopants will be discussed.
Acknowledgments: This work was supported by the National Science Centre (Contract No. DEC-2012/05/B/ST5/00720)
and party by the Polish Ministry of Science and Higher Education within Iuventus PLUS IV program (2015 - 2017),
project no. IP2014 011973.
S04-P23
Optical, Structural and Microhardness Properties of KDP Crystals Grown from
L-arginine Doped Solutions
Igor Pritula*1, Olga Bezkrovnaya1, Elena Kostenyukova1, Dmitriy Sofronov1, Elena Dolzhenkova1
1
Institute for Single Crystals SSI “Institute for Single Crystals” NAS of Ukraine,
60, Lenin Avenue, 61001, Kharkiv (Ukraine)
The hydrogen bonds present in KDP group crystals essentially contribute to nonlinear optical
phenomena such as quadratic electrooptical effect and generation of higher harmonics. To raise the
quadratic susceptibility and, consequently, the efficiency of the three-wave processes in these
crystals, in a number of investigations, for instance [1, 2], there were made attempts to incorporate
organic molecules, in particular, low-dimensional molecules of amino acids, into KDP group
crystals. Such molecules possess high polarizability due to the processes of internal charge transfer
between the donor (COO-) and the acceptor (NH2+) amino acid groups.
In the present work we studied peculiarities of the incorporation of L-arginine (L-Arg) into
KDP crystal grown by the method of temperature reduction onto a point seed. The influence of the
low-dimensional organic additive on the optical properties, structure perfection, mechanical and
laser damage threshold of KDP crystal was investigated, too.
KDP single crystals were grown from aqueous solutions onto a point seed using the temperature
reduction method by doping with different (from 0.3 to 1.4 wt.%) concentrations of L-Arg. The
polydentate characters make L-Arg more advantageous for long-range hydrogen bonding
interactions, or electrostatic interactions with positively charged groups. The optical transmission
spectrum of KDP:L-arg showed very low absorption in the entire visible region. We have observed
in the spectral changes the interaction between host material (KDP) and the guest amino acid
additive (L-Arg). The presence of the functional groups belonging to L-Arg molecule was
confirmed by FTIR-spectroscopy. The performed Raman spectroscopic studies showed that the
band of the normal modes of the tetrahedral PO43− ions were affected when the additives were used.
L-Arg molecules were found to enter in the growth sectors {100} and {101} of KDP crystal, either
due to the fact that the carboxyl and amino groups formed hydrogen bonds with the face (100) in
the former case, or, in the latter case, owing to the electrostatic interaction of the negatively charged
carboxyl groups with the positively charged (101) face. By means of the Bond method using a
multipurpose three-crystal X-ray diffractometer it was shown that the presence of L-Arg additive
increased the crystal lattice parameter a of the grown crystals, and diminished the crystal lattice
parameter c. For the first time, there was analyzed the influence of L-arg molecules on the value of
laser damage threshold for different growth sectors of KDP. The laser damage threshold was found
to rise for the growth sector {101}, and to decrease for the growth sector {100} of KDP:L-Arg with
respect to the corresponding values for the pure crystal. The Vicker`s hardness studies performed at
room temperature on the (100) and (001) crystallographic planes showed that the doping with
amino acid resulted in the decrease of the crystal’s microhardness by 5-9% and 14-18% for the
pyramidal and prismatic growth sectors, respectively.
References:
[1] Govani J., Durrer W., Manciu M., Botez C., Manciu F., J. Mater. Res., 24 (2009) 2316.
[2] Mena M., Mahadevan C., Cryst. Res. Technol., 43 (2008) 166.
S04-P24
Growth and point defect characterization of bulk AlN crystals
Carsten Hartmann, Andrea Dittmar*, Jürgen Wollweber, Sandro Kollowa, Klaus Irmscher, Frank
Langhans, Albert Kwasniewski, Matthias Bickermann
A Bulk AlN crystals with high structural perfection are a highly promising substrate material for
opto-electronic deep UV AlGaN devices with emission wavelengths λ < 300 nm where dislocation
densities DD < 106 cm-2 are required in the active layers to achieve acceptable quantum efficiencies.
From our present point of view, the homoepitaxial bulk growth by Physical Vapour Transport
(PVT) is the commonly accepted method for growing crystals of sufficient size and crystalline
quality (DD < 105 cm-2, no small-angle grain boundaries).
In this work, we report on the PVT growth of high quality single crystalline AlN based on the
comparatively small size of spontaneously nucleated AlN crystals. Therefore, a continuous crystal
enlargement is mandatory which can be realized during homoepitaxial growth over several growth
generations. Parallel to that, incorporation of impurities like O, C, and Si during growth has to be
considered, as they influence the crystal’s optical and electrical properties. Ways to control the
incorporation of these impurities during the PVT growth are pointed out.
Single AlN crystals grown by PVT were structurally characterised by rocking curves, X-ray
Lang topography, and defect-selective wet chemical etching. The crystalline perfection of the initial
seed wafers (rocking curve FWHM 11-20 arcsec) can be preserved during smooth crystal
enlargement over several crystal generations. Currently, crystals of up to 15 mm diameter with
rocking curve FWHM values between 13 and 21 arcsec across the whole surface area are obtained
(DD < 104 cm-2)[1].
O, C, and Si impurity concentrations derived from crucible as well as AlN source material are
determined by secondary ion mass spectrometry (SIMS). It is demonstrated that the impurity
incorporation can be influenced by the growth temperature, by face specific growth, and by adding
impurities into the source material. UV measurements have proven that the broad absorption band
centered at about 265 nm impairing deep-UV applications can be quenched when O or/and Si
concentrations considerably exceed the C concentration [2].
References:
[1] C. Hartmann, A. Dittmar, J. Wollweber, M. Bickermann, Semicond. Sci. Technol. 29 (2014)
084002 (10pp)]
[2] K. Irmscher et al., J. Appl. Phys. 114, 123505 (2013).
S04-P26
Crystal growth of hexaferrits Z structure Ba(Sr)3 Co2 Fe24 O41 by
floating zone melting.
A.M. Balbashov(1*, M.E. Voronchikhina(1, A.A. Mukhin(2, V.Yu. Ivanov(2, L.D. Iskhakova.(3
(1
A.M.Prokhorov General Physics Institute RAS,(Russia) (3Fiber Optics
Center RAS(Russia)
*
email:[email protected]
Moscow Power Engineering Institute,(Russia)
(2
Single crystals of hexaferrits with Z structure of Ba(Sr)3 Co2Fe24O41 are grown from the melt by
zone melting method with light heating equipment URN-2-ZM. The accurate phase diagram of
BaO(SrO)-MeO-Fe2O3 at high temperatures is unknown and the choice of growing conditions was
based on data from the phase diagrams of BaO-Fe2O3 and SrO-Fe2O3. The structure of phase
diagrams significantly depends on the partial pressure of oxygen above the melt. So crystal growth
hexaferrits has been carried out in a closed crystallization chamber and pressure was maintain
within 20-50 atm. Excess pressure of oxygen can lead to a change in valency of Co2 +, optimization
technology on this parameter was controlled on the resulting electrical conductivity of the material.
At low partial pressures of oxygen these compositions melt incongruently and the resulting single
crystal contains numerous phase inclusions, but one phase with a hexagonal structure is prevailing.
This confirmed according to the XRD and magnetic measurements. When the pressure of oxygen
above the melt increases degree of incongruent melting of composition decreases, and at 30-50 atm.
visually observed behavior of the melt zone testifies to the congruent character of the melting. As a
result of sequential selection of modes of growth conditions parameters are found close to optimal
for obtaining good quality of crystals: linear growth rate-4-5 mm/h, the speed of crystal rotationl-40
rpm, the speed of the feed rod 1-2 rpm., temperature of annealing furnace in crystal growth process
-1000oC, partial oxygen pressure in crystallization chamber -30 atm. X-ray -phase analysis
confirms the one phase structure of grown crystals. Strict maintaining the growth parameters during
run is essential for obtaining single phase material. Failure of this to do so results in the arising of
second phases, e.g. BaFe2O4, SrFe2O4. Feature of grown crystals of hexaferrits is that they are
composed of plate blocks with a thickness of up to 1-2 mm. with hexagonal plane oriented along the
axis of growth. Blocks can be disoriented relative to each other up to 1-2o. Electric resistivity of
grown crystals is at level 107-108 Ohm.cm. Measurements of magnetization depending on
temperature and magnetic field confirmed, basically, that the properties of grown hexaferrite single
crystals of Z type correspond to the known parameters for these materials. Fig.1. show
magnetization vs. magnetic field dependences for both compounds
80
4 .2 K
4 .2 K
100
70
H  c
50
H || c
40
B a 3C o 2F e 24O 41
g r o w th 2 3 .1 2 .1 4
30
H  c
80
290 K
290 K
Magnetization, emu/g
Magnetization, emu/g
60
60
H || c
40
S r3C o 2F e 24O 41
g r o w th 1 1 .0 2 .1 5
20
20
10
0
0
20
40
0
0
.
M ay 2015
20
40
M a g n e t ic f i e l d , k O e
M a g n e t ic f ie l d , k O e
M ay 2015
Fig.1. Magnetization vs. magnetic field of Ba3 Co2Fe24O41 and Sr3 Co2Fe24O41 crystals.
S04-P27
Mathematical modeling of the process of growing a single crystal CdTe 100 mm
by the Obreimov-Shubnikov method
Marina Pavlyuk*1, Ekaterina Sukhanova2, Marina Zykova2, Vladimir Kanevsky1, Igor Avetissov2
1
D. Mendeleev University of Chemical Technology of Russia, Miusskaya pl. 9, Moscow, (Russia)
2
The growth kinetics is very important from the standpoint of improving of single crystal
technology and understanding of optical and structural defects formation in the crystal during the
growth process.
A direct study of the kinetics of CdTe crystal growth is very difficult. Since the growing crystal
is well shielded, the crystallization front (FC) in the melt and its visualization is not possible.
Sometimes, in practice the FC in defective single crystals can be determined by decorating using
microbubbles or by X-ray microanalysis, which allows displaying the components distribution
along the growth axis and ingot diameter. These data could be applied to prove the results of
numerical modeling of the growth process. The task of analysis of growth kinetics of large CdTe
single crystals grown by the Obreimov-Shubnikov technique was solved by the numerical
simulation using ANSYS 14.5 Fluent software. The calculation was carried out in three steps. At
the first step we have calculated a thermal profile of an empty shaft furnace (Figure 1a). At the
second step we simulated an internal space of the furnace with a quartz ampoule and a crucible with
melt inside the ampoule (1b). At the final step we calculated the melt flows in the crucible using the
thermal conditions obtained at the previous steps. The enthalpy model was used for crystallization
simulation. The simulation results are consistent with the growth experiment results, confirming the
adequacy of the numerical model.
This work was supported by the Russian Foundation for Basic Research RFBR (grant №14-02-31726 mol_а).
a)
b)
Figure 1. Temperature distribution: a) thermal profile in the empty shaft furnace filled by air and b) thermal
profile of the inner space of the furnace with the with a quartz ampoule and a crucible with melt inside the
ampoule
S04-P28
Features compensate defects in CdTe using a stepwise cooling of the crystal
Marina Pavlyuk*1, Ilya Subbotin2, Vladimir Kanevsky1
1
2
National Research Centre "Kurchatov Institute", Akademika Kurchatova pl., 1, Moscow, (Russia)
The most important the aspect of application of CdTe is the production of detectors, X-ray and
gamma radiation, which does not require additional cooling. High prices for any kind of CdTe
crystals are caused due to a number of specific properties, difficulties in obtaining both large
structurally perfect single crystals as well as the complexity of achieving high electrophysical
parameters. The presence of phase transitions cause instability and non-reproducibility
electrophysical properties of, which are highly dependent on the conditions in which the single
crystal is grown.
In this work presents the results to study of dependence of the microstructure CdTe single
crystals grown by the Obreimov-Shubnikov method on the degree of doping of chlorine. Crystal
growth occurred of the cadmium partial pressure PCd = 1 - 1.2 atm., which led to the achievement
of the near-stoichiometric composition. Crystals were subjected to an improved post-cooling regime
in view of the four-phase transitions [1].
The concentration of Cl introduced into the melt while growing the ingot was range from 1 ·
1016 to 2 ·1019 cm-3. As a result, compensation growing crystals were characterized by p-type
conductivity.
From the phase diagram of the Cd-Te [1] follows that of repeated constriction solidus lines in
the areas of phase transitions, getting free of Te precipitates crystals is very difficult and requires
precise control of stoichiometry, or rather the composition of corresponding congruent phase
transition Effectuation this requirement and at the same time with optimal conditions of doping and
the use of improve the post-cooling regime obtained single crystals of CdTe free of Te precipitates ,
with a resistivity of > 109 Ωcm (remain unchanged for 10 years), dislocation density 1,25 · 104 cm-2
and transmittance 70% in the wavelength range of 1-25 µm.
References:
[1] Ivanov Yu., J. of Inorg. Chem., 59 (2014) 1705–1714.
S04-P30
Investigations on synthesis, growth and physical properties of AgGaInS2 single crystals
for Mid-IR application
N. Karunagaran* and P. Ramasamy
Centre for Crystal Growth, SSN College of Engineering, Kalavakkam 603110, India
The I-III-VI2 ternary semiconductor of AgGaInS2 single crystal has been grown by Bridgman
technique. Indium was partially substituted at Gallium site in chalcopyrite AgGaS2 structure. The growth of
AgGaInS2 single crystal is done in two steps. First, synthesis of the polycrystalline material from the starting
elements is achieved using melt temperature oscillation method. Secondly, the synthesized material is
employed to grow a single crystal. AgGaInS2 crystallizes with chalcopyrite structure in the space group I-42d
with unit cell parameters a = b = 5.831 Å, c = 10.876 Å. The synthesized AgGaInS2 polycrystalline charge was
confirmed by powder XRD.
Thermal property of AgGaInS2 was analyzed using differential scanning calorimetry (DSC) technique.
The melting point is 896°C and solidification temperature 862°C. The grown crystal was subjected to IR
transmission. The transmission in the IR region is 65%. The band gap energy of the AgGaIns2 single crystal is
2 eV. The stoichiometric composition of AgGaInS2 single crystal was confirmed using energy dispersive
spectrometry (EDS).
Figure 1. Single crystal ingots of AgGaInS2
S04-P31
Crystal Growth and Thermoelectric Properties of Sr2Fe2O5 Single Crystals
Hossain Md Anwar1,2*, Mori Takao2, Nagao Masanori1, Watauchi Satoshi 1 and Tanaka Isao1
1Center for Crystal Science and Technology, University of Yamanashi, Miyamae 7-32, Kofu, Yamanashi
400-8511, Japan
2 National Institute for Materials Science (NIMS), Namiki 1-1, Tsukuba 305-0044, Japan
SrFeO3- with a wide oxygen non-stoichiometry is interesting material as mixed oxide-ionic and
electron conductor at elevated temperatures. Some oxides of the brownmillerite structure with an
oxygen deficient perovskite exhibit high oxide ion mobility. At temperature below 850 ºC the
reduced ferrite SrFeO2.5 is stabilized to the orthorhombic brownmillerite (OB) structure Sr2Fe2O5
where vacancy ordering results in an alternation of layers of octahedral FeO6/2 (O) and tetrahedral
FeO4/2 (T) along the b-axis.
We reported here the floating zone growth and characterization of Sr2Fe2O5 single crystals. The
SrFeO3- crystals grown in O2 atmosphere were severely cracked at room temperature. This
cracking into the SrFeO3- crystals due to the phase transition from brownmillerite ( =0.5) to the
orthorhombic (=0.25) phase by the oxidation of Fe3+ ions to Fe4+ ions during cooling after growth
in O2 atmosphere. The dominant oxygen diffusion mechanism through such a crystal is via
microcracks rather than oxygen vacancies, while the same cracks complicate the interpretation of
transport measurements. For the low temperature transport properties and intrinsic oxygen diffusion
the cracking should be minimized. To prevent the oxidation of Fe3+ ions in SrFeO3- we tried to
grow SrFeO3-single crystals in Ar atmosphere. The crystals grown in Ar atmosphere were crack
free and twinned structure. The SrFeO3- crystals grown in Ar atmosphere were identified to be
brownmillarite type structure ( =0.5) by powder XRD.
We also studied the thermoelectric properties of Sr2Fe2O5 single crystals to check the possibility
of the materials in thermoelectric applications. Resistivity and Seebeck coefficient of the grown
crystals were measured with an ULVAC ZEM-2 in the temperature range of 200–800 ºC in He
atmosphere. Power factor was calculated from the resistivity and thermoelectric power values. The
maximum power factor (13 Wm-1K-2) was obtained at 800 ºC. In order to obtain an idea of the
thermoelectric performance, thermal conductivity was measured for the crystals with suitable
dimensions. To determine the thermal conductivity values within the same temperature range 50800 ºC, the specific heat and thermal diffusivity coefficient of the crystals were measured by using
DSC-8231 (Differential Scanning Callorimetry) and a laser flash method (ULVAC TC-7000),
respectively. The thermal conductivity of the grown crystals was determined to be 3.6 Wm-1K-1at
800 ºC. Due to high thermal conductivity ZT value became low (0.004). If it is possible to increase
electrical conductivity and reduce thermal conductivity by doping with suitable element, this
material could be a promising thermoelectric material.
Figure 1: Sr2Fe2O5 single crystal
grown by floating zone method
S04-P33
Magnetocaloric and Hopkinson effects in slowly and rapidly cooled Gd7Pd3
Oboz Monika*1, Talik Ewa1, Guzik Adam1, Zajdel Paweł1, Grzegorz Ziółkowski1
1
Institute of Physics, University of Silesia, Uniwersytecka 4, 40-007 Katowice (Poland)
Investigations of X-ray diffraction, dc and ac-magnetic susceptibility, magnetocaloric properties
and scanning electron microscopy (SEM/EDX) in order to elucidate the Hopkinson and
magnetocaloric effects in relation to the technological aspects for slowly cooled polycrystal and
rapidly cooled (rc) casts of Gd7Pd3 intermetallic compound were performed. The slowly cooled
polycrystalline samples were obtained by melt in an induction coil. The rc-cast Gd7Pd3 sample was
obtained by means of a mould casting technique. The obtained Gd7Pd3 samples crystallized in a
Th7Fe3-type hexagonal phase with space group P63mc. The gadolinium atoms in this type of
structure occupy three non-equivalent crystallographic positions (2b and 6c sites) and the Pd atoms
only one (6c position). Moreover, in the the Gd ions are located in the triangular configuration.
Monocrystalline Gd7Pd3 orders ferromagnetically below 334 K, polycrystal and powdered rccast Gd7Pd3 undergo magnetic transformation at 332 K and 331 K, respectively, while the bulk rccast Gd7Pd3 orders ferromagneticalli below 339 K.
The SEM/EDX elemental analysis showed that the sample was homogeneous and the
stoichiometry was in agreement with the nominal one. Figure 1a shows a surface of the rc-cast
material. Figure 1b shows a crystal which grew on the fringe of the rc-cast sample. The crystal habit
is in agreement with the hexagonal crystal structure of the compound. The size of the crystal is of
the order of several micrometers.
The calculated entropy changes ΔSm at 7 and 2 Tesla were -6.6 J/Kkg and -2.8 J/Kkg for the
Gd7Pd3 single crystal, -6.73 J/Kkg and -2.72 J/Kkg for polycrystal, -6.03 J/Kkg and -2.52 J/Kkg for
the rc-cast Gd7Pd3, -5.11 J/Kkg and -2.01 J/Kkg for rc-powdered samples, respectively. The
investigated ferromagnetic system is sensitive to grain size. The magnetocaloric effect and
Hopkinson peak decreases with the decrease of the grain size. The results were compared to the
data of single crystal obtained for grown by the Czochralski method from a levitating melt.
a)
b)
Figure 1. SEM images of rc-cast Gd7Pd3: a) a side view of the mould (magnification
40x), b) the twin crystal of the compound on the surface of the mould (magnification
1800x)
Acknowledgements
This work was partially financed by the Polish National Science Centre (Narodowe Centrum Nauki)
under Grant No. 2011/03/B/ST5/01035.
S04-P34
Characterization of CSBN single crystals by XRF, XRD, SEM, XPS and
electrical conductivity studies
Szubka Magdalena*1, Talik Ewa1, Kusz Joachim1, Duda Henryk1, Świrkowicz Marek 2, Winiarski Antoni1,
Kisielewski Jarosław2
1
A. Chełkowski Institute of Physics, University of Silesia, Uniwersytecka 4, 40-007 Katowice, Poland
2
Institute of Electronic Materials Technology, Wólczyńska 133, 01-919 Warsaw, Poland
The crystals of ferroelectric niobates with the structure of tungsten bronze such as SrxBa1xNb2O6 (SBN) and CaxBa1-xNb2O6 (CBN) are the subject of intense investigations in the view of
their very interesting non-linear electro-optical, dielectric, piezoelectric and pyroelectric properties.
Doping with rare earth ions additionally increases the possibility of using these crystals in laser
technology. The growth of crystals being the mixture of SBN and CBN had been also undertaken in
order to obtain materials with intermediate values of the Curie temperature.
Single crystals of ferroelectric CaxSryBa1-x-yNb2O6 (CSBN) were obtained by the Czochralski
method. Thermal system with platinum crucible and blowing of air at its bottom to change
temperature distribution in the melt (crucible base cooling) was used. The charge material was
prepared as a mixture of two compounds CBN and SBN with compositions which melt congruently.
The main formula of charge was: xCBN + (1-x)SBN. Single crystals were grown for the following
compositions: x = 0.25; 0.50 and 0.75. In case of compositions x = 0.50 and 0.75 single crystals
were also doped with neodymium. Single crystals up to 24 mm in diameter and 60 mm in length
with characteristic 24 faces were grown.
The aim of this work was determination of the chemical composition, electronic structure and
electrical conductivity examination of CSBN single crystals cut out respectively along (001) and
(100) planes. High-resolution core level spectra of the Ca 2p, Sr 3d, Nb 3d, Ba 3d, O 1s states show
that the bulk of the CSBN crystals is characterized by only one chemical state for each element,
which dominates in the structure. The difference in chemical composition in relation to nominal
value obtained from XPS, XRF and SEM analysis may result in appearance of oxygen vacancies
and some defects in the CSBN crystals. It can be reflected by electrical conductivity studies. The
order of magnitude of measured conductivity is very small. Depending on the crystallographic
direction the conductivity is anisotropic but in the case of measures in both directions the
conductivity characteristic changes in the same temperature from semiconductor to similar to
metallic. For both directions the activation energy is essentially the same. In lower temperatures one
man can observe the increase of conductivity, where the source of carriers could be probably the
defects in examined crystals. In the temperature near 370 K conductivity begins to decrease, what
can be related to the increase of scattering on crystalline network vibrations.
Figure 1. Photos of CSBN75 single crystals
S04-P35
Influence of growth parameters on electrical proprieties of highly polluted mc-Si
grown by the Bridgman technique with various crucible-coating combinations
Negrila Radu Andrei*1, Pupazan Vasile1, Vizman Daniel1
1
Faculty of Physics, West University of Timisoara, Bd. V. Parvan 4, 300223, Timisoara, Romania
In the race to improve the price of solar energy by lowering the costs for silicon solar panel
production, one of the important production segments to be addressed are the purification and
crystallization of photovoltaic grade silicon. Currently, directionally solidified multi-crystalline
silicon (mc-Si) is predominant in the market of photovoltaic silicon (2015: ~65% [1]) and is
expected to stay so during the following decade. Because of its low costs and its similarities with
directional solidification, Bridgman growth of small diameter (max. 3 cm) mc-Si is a suitable
technique for a fundamental study of the influence of growth parameters (like growth rate and
process time, temperature gradients, crucible coating) on the interface shape, grains size and
impurity distribution and precipitation, which are important parameters for the photovoltaic
applications. As silicon is crystallized in non-reusable silica crucibles with anti-sticking silicon
nitride coatings, experimental investigations have been performed on new different crucible-coating
combinations for the identification of cheaper and maybe even reusable crucible materials.
Even though an electronic grade quality Silicon feedstock was employed, a large distribution of
impurity precipitates (especially of SiC) was found in most growth experiments. A very high
neutral impurity (C and O) concentration has been found. These impurities have largely entered the
molten silicon through diffusion into the liquid phase, aided by convective transport [2]. Therefore
the impurity concentration in the melt is strongly related with the time duration in which the silicon
was in the molten phase, but also to the different coating materials that were employed. In this
work, this behavior is linked with the increasing average resistivity values and decreasing minority
carrier lifetime. While decreasing lifetime with increasing impurity concentration is a standard
prediction of the SRH electron-hole recombination model, the resistivity increase is explained by
majority carrier mobility limitation through scattering on neutral impurity centers (C and O) for
unusually high impurity concentrations (>1017 at/cm3) [3].
It seems that, for highly polluted mc-Si majority carriers, scattering on neutral impurities
mechanism prevails in limiting the carrier mobility over scattering on ionized dopants and phonons.
Therefore, the distribution of neutral impurities can be directly linked to resistivity scans for highly
polluted mc-Si through their modulation of the value of carrier mobility in areas with different
impurity concentrations. Since the impurity distribution is dependent on the convection structure,
this observation could be implemented for the experimental tracing of the convection during growth
in a DS furnace of much larger dimensions.
References:
[1] Semiconductor Equipment and Materials International (SEMI), International Technology Roadmap for
Photovoltaic (ITRPV) 2014 Results (April 2015).
[2] Popescu A., Vizman D., International Journal of Heat and Mass Transfer, 54 (2011), 5540.
[3] Kireev P. S., Semiconductor Physics, Mir Publishers (1978).
S04-P40
Optical properties of Cd1-xMnxTe:Fe2+ crystals
O.K.Kapustnyk1*, N.O.Kovalenko1, I.S.Terzin1, P.V.Mateychenko1, D.S.Sofronov2, A.G.Fedorov3
1
Institute for Single Crystals of NAS of Ukraine, Lenina Ave. 60,Kharkiv (Ukraine)
STC "Institute for Single Crystals" of NAS of Ukraine, Lenina Ave. 60,Kharkiv (Ukraine)
3
Institute for Scintillation Materials of NAS of Ukraine, Lenina Ave. 60, Kharkiv (Ukraine)
2
Lasing range expansion is one of the main tasks of laser materials science. For chalcogenide
active media it can be solved by creating a new hosts based on the solid solutions of chalcogenides.
Analysis of the existing literature [1-4] shows that the most promising material for shifting
of the lasing band toward longer wavelengths is Cd1-хMnхTe. Currently, the literature describes the
optical properties of a solid solution of Cd1-хMnхTe:Fe2+ with the only one value of the manganese
concentration x = 0.45 [4]. The article shows the potential of the given material for the lasing band
shifting to longer wavelengths of the optical spectrum. However, the studies were carried out for
one solid solution composition only. Thus, great interest is to obtain a series of solid solutions
Cd1-хMnхTe:Fe2+ and to study their optical properties to obtain an understanding of the relationship
between the structural parameters of the crystalline host and optical properties of the active ion.
Crystals of a solid solution Cd1-хMnхTe:Fe2+ were grown by the Bridgman method under
overpressure of an inert gas. Optical spectrophotometry for visible, near and mid-infrared regions
was performed by a spectrophotometer PerkinElmer Lambda 35 and PerkinElmer Spectrum One.
The elemental composition of the obtained samples was defined by an electron microscope with the
energy dispersive microanalysis system. XRD analysis has been used for investigation of structural
properties.
The series of the solid solution Cd1-хMnхTe:Fe2+ crystals for the concentration range x
between 0.09 to 0.52 was grown. Absorption spectra in the mid-IR and visible ranges of the optical
spectrum are studied. The correlation between the solid solution Cd1-хMnхTe composition,
structural properties and the maxima positions of the Jahn-Teller components of the Fe2+ ions
absorption cross section was shown. Obtained results can be used for prediction of possible lasing
range for CdMnTe:Fe2+ active media.
References:
[1] V.V. Fedorov, W. Mallory, S.B. Mirov, U. Hömmerich, S.B. Trivedi, W. Palosz, “Iron-doped CdxMn1−xTe crystals
for mid-IR room-temperature lasers”, Journal of Crystal Growth, V. 310, Issue 20, 1 October 2008, Pages 4438–4442.
[2] M. Mond, D. Albrecht, E. Heumann, G. Huber, S. Kück, V. I. Levchenko, V. N. Yakimovich, V. G. Shcherbitsky,
V. E. Kisel, N. V. Kuleshov, M. Rattunde, J. Schmitz, R. Kiefer, and J. Wagner, "1.9- μm and 2.0- μm laser diode
pumping of Cr2+:ZnSe and Cr2+:CdMnTe," Opt. Lett. 27, 1034-1036 (2002).
[3] A.V Podlipensky, V.G Shcherbitsky, M.I Demchuk, N.V Kuleshov, V.I Levchenko, V.N Yakimovich, S Girard, R
Moncorgé, “Cr2+:Cd0.55Mn0.45Te crystal as a new saturable absorber for 2 μm lasers”, Optics Communications, Volume
192, Issues 1–2, 15 May 2001, Pages 65–68.
[4] S. B. Trivedi, C.C.Wang, S. Kutcher, U. Hommerich, W. Palosz, “Crystal Growth Technology of Binary and
Ternary II-VI Semiconductors for Photonic Applications”, Journal of Crystal Growth, 310, 2008, 1099-1106.
S04-P41
Growth of Bi2Te3, Cr2Ge2Te6 and CrSi2Te6 crystals for Topological Interests
C.Bagavath1*,R.MohanKumar1,T.Shalini1,J. Kumar1, C. Ferrari2, L. Nasi2, L. Lazzarini2
1Crystal
Growth Centre, Anna University, Chennai – 600025INDIA.
2IMEM-CNR
Institute, Parco Area delle Scienze 37/A Parma – 43124, Italy
*e-mail :[email protected], [email protected]
In recent years, topological insulators are considered to be a hot research topic in condensed matter
physics, motivating further development of the concept of topology in materials studies. Bismuth Telluride
(Bi2Te3) is a narrow gap layered semiconductor with a hexagonal (or rhombohedral) close-packed structure.
Bi2Te3 has a direct band gap of 0.21eV and it possesses high anisotropic electrical and thermal conductivity.
When alloyed with antimony or selenium, it acts as an efficient thermoelectric material for refrigeration or
portable power generation. In addition to its role as a thermoelectric material, bismuth telluride is also one of
the most commonly studied topological insulators (TIs) to date.
In our present study, single crystals of Bi2Te3 have been grown by Chemical Vapor Transport (CVT)
method. Stoichiometric amounts of high purity bismuth and tellurium were taken in a quartz ampoule, sealed
and kept at 773 K for 8 hours. The synthesized material was ground into a fine powder and was taken in a
fresh quartz ampoule with Iodine as the transporting agent and was sealed. By using a two zone horizontal
resistive heating furnace, the source and growth temperature was maintained at 823 K and 698 K respectively.
The source and growth zone temperatures were changed in order to achieve good nucleation and they were
maintained at a constant temperature for 15 days to obtain good quality single crystals of Bi2Te3.
Cr2Ge2Te6 is particularly interesting since it is in the very rare class of ferromagnetic insulators, and
possesses a layered, nearly two dimensional structure. Recently, this material has been revisited due to its
small lattice mismatch with the topological insulator Bi2Te3, making it an ideal candidate as a substrate for
devices. In the present study, Cr2Ge2Te6 and CrSi2Te6 single crystals were grown by self- flux Bridgman
method. High purity powders of Cr,Ge,Te were mixed in the molar ratio of 1:1:6 with excess of 20% Te which
acts as a flux. Similarly, Cr,Si,Te powders were mixed in the molar ratio of 1:2:6.The mixture is heated to 1273
K for 8 days and later annealed at 973 K under argon atmosphere in order to remove the excess Te. Structural
investigations using X-ray diffraction and Raman confirmed the crystallinity of rhombohedral Cr2Ge2Te6 and
CrSi2Te6 single crystals. The SEM images shows step like growth features. AFM and MFM studies were also
done and the details will be presented.
S04-P42
Characterization of G2-sized quasi-mono Si directionally solidified in TMF
Frank M. Kiessling2,*, Natasha Dropka1, Christiane Frank-Rotsch1, Torunn Ervik1, Dieter Linke1,
Robert Menzel1, Thomas Richter2, Lamine Sylla2
1
2
Leibniz-Institut für Kristallzüchtung (IKZ), Max-Born-Str. 2, D-12489 Berlin (Germany)
SolarWorld Innovations GmbH, Berthelsdorfer Straße 111 A, 09599 Freiberg/Sachsen (Germany)
The motivation for improving the performance of solar cells is high, as this leads to a significant
cost reduction in terms of price/Wp. Directional solidification (DS) is the standard process for
large-scale production of multi-crystalline Si ingots for Si-based solar cells. A strong focus towards
higher efficiencies by reducing lifetime limiting defects forces manufacturers to develop new
growth technologies. The last few years have seen several new approaches, which aim to eliminate
or mitigate the defect density in DS-Si. One of these approaches is the growth of quasi-mono ingots
using seeds on the bottom of the crucible. In addition to the challenging growth process, multiple
seeds are needed. It is essential to control defects from the seed junctions [1] as well as those
formed at the crucible walls. Grains and their boundaries are known to be major sources for the
development of unfavorable recombination active dislocation clusters. In order to study the
influence of travelling magnetic fields (TMFs) on the growth conditions and, hence, the defect
development, quasi-mono silicon ingots have been directionally solidified in a vertical gradient
freeze-type furnace equipped with KRISTMAG-heaters [2]. As-grown G2-sized silicon ingots of
38 x 38 x 23 cm3 in volume were cut vertically and their defect structure was analysed. Information
was obtained on the curvature of the solid-liquid interface, the grains nucleated at the crucible walls
and the electrical activity of dislocations. A main focus of this investigation was the control of
dislocation formation, which can easily originate from the seed junction (see Fig. 1a and 1b).
a)
b) Figure1 a) Bottow view on the as grown ingot showing the fully geometry of the used seed.
b) Photoluminescence image of a vertical cut. No dislocation cascade is observed in the middle,
which are known to originate from the junction between the two seeds.
References:
[1] M.G. Tsoutsouva,V.A. Oliveira, D. Camel, J. Baruchel, B. Marie, and T.A. Lafford, Acta Materialia 88
(2015) 112-120.
[2] D. Linke, N. Dropka, F.M. Kiessling, M. König, J. Krause, R.-P. Lange, D. Sontag, Solar Energy
Materials and Solar Cells 130 (2014) 652-660.
*
Corresponding author, phone / fax: ++ 49 (30) 63 92 30 33 / 30 03, E‐mail: frank.kiessling@ikz‐berlin.de S04-P43
β-Ga2O3 Crystals Grown from Al2O3-Ga2O3 Melt
Nikolaev Vladimir1,2,3, Maslov Viktor1,2*, Krymov Vladimir 1,2, Kalashnikov Evgenij4, Romanov Alexey1,2
1
Ioffe Physical Technical Institute, 26 Politekhnicheskaya str., Saint Petersburg, 194021 Russia
2
ITMO University, 49 Kronverkskiy prospect, Saint Petersburg, 197101, Russia
3
Perfect Crystals LLC, 28 Politekhnicheskaya str., Saint Petersburg, 194064 Russia
4
MGOU, Radio str., 10, Moscow, 105005, Russia.
Tabular β-Ga2O3 single crystals (Fig.1) were grown by free crystallization from Ga2O3 -Al2O3
melt in sapphire crucible [1]. Growth mechanisms and properties of the crystals have been studied;
main features of optical and mechanical behavior of the crystals have been revealed.
It was shown some cleavage planes in the crystals; parallel to the pinacoid and monohedron planes
are perfect; parallel to the planes of the rhombic prisms are imperfect. The crystals had block
structure and some pores with diameter from 0,01 to 0,5 mm. The total content of Al in grown
crystals was about 5 at. %. The cleaved crystal plates have been successfully tested for gas transport
epitaxial growth of nitride semiconductor films [2].
Figure 1. Single crystal β-Ga2O3 plate
References:
[1] V.N. Maslov, V.M. Krymov, M.N. Blashenkov, A. A. Golovatenko, V.I. Nikolaev, Tech. Phys. Lett. 40
(2014) 303–305
[2] V.I. Nikolaev, A.I. Pechnikov, V.N. Maslov, A.A. Golovatenko, V.M. Krymov, S.I. Stepanov,
V.E. Bougrov, A.E.Romanov GaN growth on β-Ga2 O3 substrates by HVPE, Materials Phys. and Mechanics
22 (2015) 59–63.
S04-P44
Growth, structural and magnetic characterization of highly ordered Co2FeSi
single crystals
R. Mohankumar*1, M. Manivel Raja2, S. Ganesamoorthy3, J. Kumar*1, C. Ferrari4, L. Nasi4, L. Lazzarini4
1
Crystal Growth Centre, Anna University, Chennai – 600 025, India.
Defence Metallurgical Research Laboratory, Hyderabad – 500 058, India.
3
Material Science Group, IGCAR, Kalpakkam – 603102, India.
4
IMEM-CNR Institute, Parco Area delle Scienze 37/A Parma – 43124, Italy.
*email :[email protected], [email protected]
2
Half metallic ferromagnets are expected to make spintronic devices such as magnetic tunnel
junctions (MTJ) and spin injectors, due to their high spin polarized current to semiconductors [1].
Among the Half metallic ferromagnets Heusler type Co2FeSi crystallizes in L21 structure and has
received considerable attention due to its high Curie temperature (1100 K), complete spin
polarization and high magnetic moment (5.97 µB) [2].
Alloying of ternary intermetallics always ends up with several disorders (A2 type, B2 Type and
Do3 type) and this shows challenges to separate its intrinsic and extrinsic properties. Hence, the
growth and characterization of high quality single crystals are required to get more information on
its intrinsic properties. Co2FeSi single crystals are grown using four mirror optical floating zone
technique under Ar atmosphere. High pure arc melted polycrystalline Co2FeSi alloy was used for
seed and feed rod preparation.
The presence of L21 ordering in grown single crystalline Co2FeSi was confirmed using X-Ray
Diffraction and Mössbauer spectroscopic measurements. The measured magnetic moment agrees
well with that of the magnetic moment calculated using DFT calculations [3].
References:
[1] Felser C., Fecher G. H., Spintronics: From Materials to Devices, Springer, Berlin (2012).
[2] Wurmehl S., Fecher G. H., Kandpal H. C., Ksenofontov V., Felser C., Phy Rev B, 72 (2005) 184434.
[3] Mohankumar R., Ramasubramaniyan S., Rajagopalan M., Manivel Raja M., Kamat S. V., Kumar J.,
J. Mater. Sci, 50 (2015) 1287.
S04-P45
Effect of crucible geometry and fixed heat exchangers in the solid-liquid
interface for growing CdZnTe bulk crystals using a Vertical Gradient Freeze
technique
REPISO Eva 1, CORROCHANO Alvaro1, RUBIO Sandra1, PLAZA Jose Luis1, TSYBRII Zinoviia2,
VUICHYK Mykola2, DIEGUEZ Ernesto1*
1
Depart. Physics of Materials, Universidad Autónoma de Madrid (UAM), Madrid (Spain)
2
Institute of Semiconductor Physics (ISP), Kiev (Ukraine)
CdTe alloy materials are extensively used on security and medical applications as bulk
materials, in particular CdZnTe (Zn=4%) (CZT) could be the key for achieving the realization of
drugs and explosive detectors [1]. This material presents many difficulties in the bulk growth to get
large size, free from defects and homogenous dopant material along the whole ingot; but the
crucible shape and the heat exchange have been considered as key parameters that considerably
influence the material quality [2]. On the other hand, the simulations carried out in the frame of the
crystal growth processes have revealed to give very helpful approaches for improving the materials
quality, giving clear indications of the best experimental results [3].
In this work, the commercial CrysMAS code has been used in order to select the best growth
conditions in the case of bulk CZT crystals by the Vertical Gradient Freeze (VGF) technique. The
boundary conditions have been chosen from the geometry of the VGF equipment available in the
laboratory, which is normally applied for growing two inches CZT diameter crystals, together with
the real temperature gradients from a real CZT bulk growth.
Different PBN crucible with quartz envelopes geometries such as flat, conical and seeded
bottom shaped have been simulated, with and without the attachment of a heat exchanger system,
considering the growth rate and the shape of the solid-liquid interface as the critical parameters for
selection of the preferential geometry. It has been found that the conical shape provides no
significant benefits over the flat one, owing that a convex interface is never obtained when the
shape of the crucible is constant. Otherwise the implementation of a hollow cylinder of Pt, W, PBN
and SiC has been analyzed with the objective of improving the solid-liquid interface. The results of
the simulation when a W hollow cylinder is used as heat exchanger in a flat crucible bottom shows
an improvement in the shape of the solid liquid interface with a slightly convex interface shape
along the half part of the growth ingot, a situation which is more complex when other bottom
shaped conical crucible are used. Results related with the seeded bottom crucible together with the
possibility of a movable heat exchanger will be discussed.
References:
[1] M. C. Kemp, IEEE 1, 1 (2011) 282-292
[2] V. Carcelén, N. Vijayan, E. Dieguez, A. Zappettini, M. Zha, L. Sylla, A. Fauler and M. Fiederle, Journal
of Optoelectronics and Advanced Materials, 10 11 (2008) 3135-3140
[3] N. Zhang, H. G. Park, J. J. Derby, Journal of Crystal Growth, 367 (2013) 27-34
S04-P47
High purity Germanium Crystal Growth
Aravazhi Shanmugam
Umicore Electro-Optic Materials
Watertorenstraat 33
B-2250, Olen
Belgium
Email : [email protected]
High purity germanium crystals (HPGe) are excellent candidates for high resolution gamma ray detection and recently for dark matter research
(WIMP). In this regard, worldwide attention has been focused on fulfilling the crystal growth needs of high quality HPGe crystals of increasing size
and narrow purity range. Unlike standard Czochralski germanium crystal growth that focuses on the dislocation free nature of crystals with excellent
dopant control; the prerequisite for HPGe growth are (1) an ultra clean crystal growth process such that extremely stringent purity levels can be
reached and (2) a special crystal growth control in order to meet the specific crystalline quality and boule size. Since the early 50’s, UM-EOM
started with the production of high quality germanium crystals for a wide range of applications : electronic, micro-electronic, infrared and high purity
Ge. Over the past decades, Umicore Electro-Optic Materials (UM-EOM) has established itself as a world leader in most of these fields. During the
presentation, an overview of the crystal growth capabilities of HPGe at UM-EOM will be given. The importance of various crystal specifications,
growth methods and characterization methods will be discussed. This work forms a basis for the successful production of high quality HPGe
crystals to meet the ever more stringent specifications, like increased boule size and reduced impurity range.
Key Words: Germanium, crystal growth, high purity materials, gamma ray detection, dark matter
S04-P48
The influence of finite silicon electrical conductivity on melt flow and dopant
transport in floating zone crystal growth process
Kirils Surovovs*1, Andrejs Sabanskis1, Janis Virbulis1
1
University of Latvia, Zellu street 8, LV-1002, Riga (Latvia)
Present work is devoted to the numerical modelling of silicon single crystal growth with
floating zone (FZ) method (Figure 1.a). A 4 inch system from Institute for Crystal Growth, Berlin is
used [1].
Specific attention is paid to calculation of electromagnetic (EM) field in the vicinity of external
triple point, where the previously used high-frequency approximation with surface currents is less
precise due to significant difference between conductivities of solid and liquid silicon. Local 2D (in
Figure 1.b heat source density Q is shown) and 3D volumetric calculations of EM field in the
vicinity of external triple point showed significantly more power in melt and less – in crystal.
Calculated redistribution of electric current is parameterized and used in more precise simulations
of interface shapes and melt flow.
Melt flow and dopant transport are calculated using FZSiFOAM program, which is based on
OpenFOAM code library. It calculates non-stationary melt flow, temperature and dopant
concentration. A sample of obtained temperature field is shown in Figure 1.c. To describe induced
heat sources and Lorentz force more precisely, changes in the boundary conditions of existing
programs are applied. Modifications are verified by comparing calculated radial electrical resistivity
distributions with experiments for various crystal pulling rates (see Figure 1.d and 1.e for radial
resistivity profiles). It was shown that concentration boundary conditions on the free melt surface
are more important than the precise description of local EM field near the external triple point.
Figure 1. a) Overall scheme of FZ system; b) Heat source density in silicon from 2D EM calculations; c)Temperature
field from 3D melt flow calculations; d) Radial resistivity distribution in obtained crystal for different crystal pulling
velocities; e) Average crystal resistivity (solid lines) and deflection of the resistivity profile (dashed lines) for different
crystal pulling velocities.
References:
[1] R. Menzel., “Growth conditions for large diameter FZ Si single crystals”, Ph. D. Thesis, Technischen
Universität Berlin, 2013.
S04-P49
3D simulation of feed rod melting in floating zone silicon single crystal growth
Plāte Matīss*1, Krauze Armands1,Virbulis Jānis1
1
Faculty of Physics and Mathematics, University of Latvia, Zeļļu 8, Rīga, Latvia
*[email protected]
A three dimensional (3D) transient model of the feed rod melting in the floating zone (FZ)
silicon single crystal growth process is presented. The system geometry [1] and process parameters
from a converged state of quasi-stationary axisymmetric calculations of global heat transfer and
phase boundaries are used as initial condition for the time dependent simulations. Introduction to
the considered FZ process is given in Fig. 1. Transient models of the 3D heat conduction, highfrequency electromagnetic field and the fluid film [2] are coupled to obtain the local melting rate on
the open melting front.
The calculations show that the inductor slit configuration determines the melting rate
distribution, and the azimuthal profile of the feed rod rim stabilizes in few rotation periods, see Fig.
2. A study of varied feed rod and inductor parameters is carried out. Although the absolute changes
of feed rod profile shape do not exceed 1 mm for the investigated parameter range, these differences
are crucial when comparing the simulations with experimental data.
Feed rod
Inductor
Melt
Crystal
C
B
A
Figure 1. Introduction to the considered FZ process. Panel A: 3D model of the 4” FZ system. Panel
B: discretization of the feed rod domain with finite element mesh used to obtain the initial state
(left) and finite volume mesh for the transient heat transfer calculations (right). Panel C:
temperature field and the modelled surfaces given as 1 – melting interface, 2 – open melting front
and 3 – feed rod side surface.
vm, mm/min
Figure 2. Left: distribution of the local melting rate on the open melting front of a converged state.
Right: azimuthal profile of the feed rod rim at various time instants during the transient simulation.
References:
[1] Rost H.-J., Menzel R., Luedge A., Riemann H. Journal of Crystal Growth, 360 (2012) pp. 43 – 46
[2] Ratnieks G., Muiznieks A., Muhlbauer A., Journal of Crystal Growth, 255 (2003) pp. 227 – 240
S04-P50
Crystal growth and characterization of an oxy-fluoride crystal (BaCaBO3F)
doped with Yb3 ions for self-frequency doubling: a thrilling challenge
Federico Khaled1, Suchinda Sattayaporn1, Pascal Loiseau1, Gérard Aka1, and Lucian Gheorghe2
1
PSL Research University, Chimie ParisTech – CNRS, Institut de Recherche de Chimie Paris, 75005 Paris, France
2
National Institute for Laser, Plasma and Radiation Physics - LSSQE, Bucharest Romania
Self-frequency doubling crystals are very promising materials because they allow efficient
emission in the visible range from high-efficient frequency conversion of the solid-state infrared
laser emissions, while being very compact. We will present the crystal growth and the potential as
SFD candidate of an oxy-fluoride crystal that can be obtained by the Czochralski method:
Yb:BaCaBO3F (YB:BCBF). This compound presents a congruent melting behavior at 1100°C.
Based on ionic radii, Yb3+ luminescent ions are assumed to substitute for Ca2+ ions. Therefore,
two different mechanisms for charge compensation might occur: cationic co-doping with Na+ in the
Ca2+ site, leading to BaCa1-2xYbxNaxBO3F, or anionic replacement of fluoride by oxygen, leading to
BaCa1-xYbxBO3(F1-xOx). The atmosphere (N2) and the nature of the crucible (Pt) were optimized for
the growth of the un-doped material. According to crystal growth experiments (Fig 1), the first
mechanism seems to be the most favorable towards getting good optical quality crystals.
Even though only one insertion site for rare-earth ions was assumed, low-temperature
absorption and EPR spectra tend to indicate multiple environments for the Yb3+ ions. Along with
that, the segregation coefficient of Yb3+ was found to be close to 3 (measurements done by ICPAES and EDX), while the one for Na+ charge compensating ions is lower than unity. All this leads
to some naked eye defects (precipitate phases and scattering centers), lowering the crystal quality
compared to the un-doped material. Also, the replacement of some Ba2+ by Sr2+ was attempted to
improve the mechanical properties. By the way, better crystal quality with less naked eyed defects
was observed.
Recently, the author of [1] assumed a reversible phase transition from space group R3to space
group P-62m at 242°C in the undoped material, linked to the rearrangement of some (BO3)3- groups
in the (ab) plane. However XRD experiments on samples with more than 1%at Yb3+ do not present
the R3 superstructure peaks at room temperature. Moreover, Raman analysis on samples with
different Yb3+ concentration indicates a different behavior. Two hypotheses can be made: either the
ytterbium helps to stabilize the P-62m structure at room temperature, either ytterbium ions create
disorder leading to a more symmetric apparent structure.
The inhomogeneous ytterbium concentration along the crystal is not convenient for obtaining
optical and laser applications. Therefore, the key issue for using Yb:BCBF as a SFD crystal remains
the crystal growth. Crystal growth experiments, along with spectral properties and early infrared
laser operation will be presented. Fig 1. BCBF crystals doped with Yb3+ (left), co-doped Yb3+/ Na+ (middle) and co-doped Yb3+/ Na+/ Sr2+ (right)
References:
[1] R.K. Li et al., J. Cryst. Growth, 382 (2013), pp 47-51.
S04-P51
Ge-containing Quartz Single Crystals - New Advanced Piezoelectric Material
Balitsky S.Vladimir*1, Balitsky V. Denis2, Balitskaya V. Liudmila1, Setkova V. Tatiana1, Nekrasov N. Aleksey1
1
Institute of Experimental Mineralogy RAS, Acad.Osipian 4, Chernogolovka (Russia)
2
Baccarat (France)
This work describes some problems of crystal growth and main properties of Ge-containing αquartz a new piezoelectric monocrystalline material. Natural and synthetic quartz are used widely in
piezoengineering, acoustoelectronics, optics and other fields of science and technics for many years.
Piezoelectric constants as well electromechanical coupling coefficient of quartz are lower than for
other piezoelectric (germanium dioxide, gallium orthophosphate, berlinite, langasites et al.), but the
quality factor is higher. The performance of piezoelectric quartz elements is limited by temperature
of 280–290°С because of proximity of phase transformation and as a result: frequency drift is
observed. That is why, a development of new more effective piezoelectric materials, which have
relatively high quality factor and in the same time work at high temperatures (400–800°С) is actual.
In last 15 years, the gallium orthophosphate (α-GaPO4) and some langasites were more perspective
single crystal materials. However, growth of large and perfect crystals involves a lot of technical
difficulties as for example for GaPO4: absence of large and quality seeds and twins. From other
hand, the langasites are very inhomogeneous because of complex composition, so the quality factor
is low.
This work shows scientific substantiates of reliable laboratory method of single crystal s growth
of Ge-containing quartz based on study of morphology of crystals, internal structure and
determination of piezoelectric properties. The quite perfect single crystals of Ge-containing quartz
with content of GeO2 12-14 wt. % were grown in aqueous fluoride fluids at temperatures of 500600°C and pressures of 70-150 MPa. Piezoelectric characteristics of the as-grown crystals are near
to gallium orthophosphate, α → β transition is increased to 840°C and it rises more at increasing of
germanium content. The elements prepared from germanium quartz are greatly increase the
temperature limits of equipment operability. The electromechanical coupling coefficient of Gecontaining quartz is also near to gallium orthophosphate. Dielectric loss tangent of Ge-containing
quartz single crystals in two to three orders of magnitude lower than that of natural and standard
synthetic quartz.
Thus, the experimental results allow consider single crystals of high germanium quartz as
promising piezoelectric material which is suitable for many traditional piezoelectric applications
and in new high performant engines as a component of combustion control. The use of Gecontaining quartz single crystals can contribute to efficiency of combustion and solving one of the
major environmental problems of the limitation of ejections of CO2 and CO to the atmosphere.
This work was supported by RFBR (Grant 14-42-03654).
S04-P52
Dislocation multiplication during Czochralski growth of germanium: Numerical
studies and experimental results
Miller Wolfram*1, Czupalla Matthias1, Abrosimov Nikolay1, Uta Juda1
1
The growth of germanium crystals with well-defined dislocation densities by means of
Czochralski method is still a challenge. Especially, when growing germanium crystals with high
purity by inductive heating the control of the thermal field inside the crystal during the growth
process becomes difficult.
Wang et al. measured the dislocation density as a function of the vertical position in the crystal
grown [1]. They compared the data with a computed ones based on the vertical temperature
gradient. The radial distribution was not considered.
We studied the thermal stress and the evolution of the dislocation density by means of dynamic
global simulations employing the software tool CGsim. The Alexander-Haasen-Sumino model is
used to compute the evolution of the dislocation density. However, there is some uncertainty in the
value of some input parameters. Therefore, we have checked the influence of certain parameters on
the dislocation density by varying the parameters and performing several runs for the same growth
process.
Another point of investigations was the thermal field in the vicinity of the melt/crystal interface.
It is significantly influenced by the melt convection. On the other hand the thermal field is critical
for the evolution of dislocation especially in this region because of its high temperature and hence
of high velocity of dislocations.
The numerical simulations have been performed for the furnace geometry and parameters of
real growth experiments. The results of the calculations will discussed in comparison with the etch
pit density measurements on wafers from these experiments.
References:
[1] Guojian Wang,Yutong Guan, Hao Mei, Dongming Mei, Gang Yang, Jayesh Govani, J. Crystal Growth
393 (2014) 54
Acknowledgement
The help of Vasif Mamedov, Kirill Mazaev, and Andrey Smirnov in setting up the runs is gratefully
acknowledged.
S04-P54
New technological approaches for electroless deposition of metal contacts on
CdZnTe single crystals.
Manuele Bettelli*1, Giacomo Benassi2, Lucia Nasi1, Nicola Zambelli2, Davide Calestani1, Enos Gombia1,
Leonardo Abbene3, Fabio Principato3, Andrea Zappettini1
1
IMEM-CNR, Parco delle Scienze 37A, Parma (Italy)
due2lab s.r.l., Parco delle Scienze 37A, Parma (Italy)
3
Dept. of Physics and Chemistry, University of Palermo, Palermo (Italy)
*[email protected]
2
Since many years our group growth Cd0.9Zn0.1Te with Boron Oxide Encapsulated Vertical
Bridgman technique. The encapsulant prevents the contact between the growing crystal and the
crucible quartz, thus improveing the quality of grown material. The monocrystalline material can be
used to realize X-ray detectors, a major issue for their preparation being the deposition of the
contacts. In particular, due to CdZnTe thermal instability above 150 degree Celsius, thermal
annealing of contacts after deposition is not possible. Also for this reason, mechanical stability of
contacts is usually poor.
For the deposition of contacts we have adopted the electroless technique which is more rapid
and economic then thermal evaporated or sputtering.
Blocking contacts are usually adopted to realize high-resolution spectrometers, where
minimization of dark current is required.
On the other hand, one of the main exploitation fields for CdZnTe detectors is related to high
flux applications. In this case, the use of ohmic contacts is preferred due to their capability to
extract with high efficiency photo-generated carriers. Indium is traditionally employed to realize
ohmic contacts on high resistivity CdZnTe crystals. However, indium electroless deposition is not
easy, and evaporated Indium contacts usually show a poor mechanical stability.
In this work, we describe a procedure to obtain gold and nickel contacts by electroless
deposition. Deposited layer thickness up to 1 micron has been obtained. Current-voltage
characterization has been carried out, paying attention to cut surface conduction by using a guardring. A ohmic behavior was found for nickel contacts and the contact resistivity seemed to be
negligible with respect to material resistivity that is very important to have a high and homogenous
electric field in the detector. Gold contacts showed blocking characteristic. In order to improve the
mechanical stability of this contacts we have replaced the solvent in the electroless solution, a very
good result was been obtained with the replacement of water with methanol.
The obtained layers show good adhesion and can withstand standard tape test. EDS-TEM
investigations demonstrate that in both the cases, the good adhesion is correlated with the good
CdZnTe stoichiometry under the contact layer.
CdZnTe planar detectors have been realized and spectroscopic characteristics have been
obtained. Detectors with symmetric nickel contacts have been compared with detectors realized
with nickel and gold contacts.
In this work, the response of detectors with nickel contacts under high flux conditions is tested
and reported.
S04-P55
Impurity distribution in characteristic of multicrystalline silicon growth mode
Nepomnyashchikh A.I., Presnjakov R.V.
Vinogradov Institute of Geochemistry SB RAS, Irkutsk, 664033, Russia
[email protected]
At present multicrystalline silicon (mc-Si) is the basic material for solar cell production [1].
The basic problem restraining solar energy growth is the price for raw silicon. From this viewpoint,
mostly promising is the refined metallurgical silicon with substance proportion from 99.9 at.% to
99.999 at.% in approaching to the regions of impurity solid solutions in silicon [2]. The key issue is
to define the limit of impurity concentrations for refined silicon to obtain the material with set
properties. The directional solidification of silicon proceeds along with segregation of metal
impurities and formation of macro- and micro structure of the ingot. The features of heat and mass
transfer, which set the parameters of growth process (e.g. velocity and gradients), affect the
effective distribution coefficient of impurities. Experimental ingots mc-Si based on metallurgical
silicon of set composition (Table 1) were grown under optimum conditions: 1) rotation of cruciblemelt-crystal with minimum rate sufficient to equalize the thermal field; 2) movement of the
crucible-melt-crystal in the zone with temperature gradient at sufficiently low rate to prevent
concentration supercooling at the crystal interface [3].
The result of calculation of the effective distribution coefficients (keff) of these elements in
the approximation of complete mixing of the melt (1) shows reduction of their values (Table 1) at
increasing the impurity concentrations in the initial charge (C0):
C  C 0 k eff (1  f )
k eff  1
(1),
where f is the fraction of crystallized silicon.
Table 1. Main element contents in the initial charges to grow mc-Si (C0, × 1016 cm-3), effective
distribution coefficients of impurities corresponding to charges № 1-5, Cl - solubility limit (× 1016
cm-3) [2]
№1
№2
№3
№4
№5
Cl
Fe
C0
keff
8450 0,002
61
0,015
53
0,02
18
0,04
2,6
1,3
Ni
V
C0
keff
C0
keff
387 0,006 544 0,00004
1,0 0,04 2,7 0,0015
0,73 0,04 6,0 0,00015
0,21 0,04 2,0
0,003
0,03
0,3
0,01
1,0
0,03
Ge
C0
keff
13
0,33
0,008 0,33
0,02
0,33
0,01
0,33
0,002
unlimited
Mn
C0
342
0,39
1,0
0,29
0,04
keff
0,001
0,017
0,035
1,5
Co
C0
734
1,8
4,6
1,6
0,2
keff
0,00001
0,001
0,0002
0,0005
4,0
We have identified the pattern of impurity distribution in the mc-Si ingots, indicating that
the free convection in the melt takes place along with the significant impact of the diffusion
substance transfer. With this in mind, we believe that for higher physical quality of mc-Si ingot the
increased purity of raw silicon is the necessary condition, and the growth mode corresponding to
this purity is a sufficient condition.
References:
1.
Global market outlook for photovoltaics 2013-2017. (http://www.epia.org/)
2.
Nakajima K., Usami N. Crystal growth of silicon for solar cells. – Springer Berlin Heidelberg. – 2009. – 259 p.
3.
Nepomnyashchikh A.I., Presnyakov R.V., Eliseev I.A., Sokol'nikova Y.V. Specific features of multicrystalline
silicon growth from high-purity commercial silicon // Technical Physics Letters, 37, 8 (2011) 739-742.
S04-P56
Growth of TbFe0.5Mn0.5O3 and Tb0.5Sr0.5MnO3 Single Crystals Using Optical
Float-Zone Technique
Hariharan Nhalil and Suja Elizabeth
Department of Physics, Indian Institute of Science, Bangalore, India 560012
Single crystal growth of two materials, TbFe0.5Mn0.5O3 and Tb0.5Sr0.5MnO3, are discussed in detail.
Both TbFe0.5Mn0.5O3 and Tb0.5Sr0.5MnO3 show interesting magnetic properties .TbFe0.5Mn0.5O3
single crystal is grown by optical float-zone method. High purity precursors Tb4O7, Fe2O3 and
MnO2 are taken in stoichiometric ratio and mixed thoroughly using a mortar and pestle for several
hours. After mixing properly, the material is sintered at 1200 °C for 24 hours. The sintered material
is again mixed properly and calcined at 1250 °C for another 24 hours. The phase purity of the
synthesized material is confirmed through room temperature powder XRD. Once the phase purity is
confirmed, the powdered sample is made into ingots of sufficient length to be used as the feed rod
in the optical float-zone furnace. A small piece of the same rod can be used as seed rod. Growth
was performed at ambient pressure and in air atmosphere. The growth rate was 5mm/hr and the
upper and lower shaft rotation rates being 30 and 35 rotations/min, respectively. Tb0.5Sr0.5MnO3
single crystal is also grown optical float-zone technique. High purity precursors Tb4O7, SrCO3 and
MnO2 taken in stoichiometric ratio are mixed thoroughly using a mortar and pestle. After mixing
properly, the material is sintered first at 1250 °C for 24 hours and again at 1300 °C for another 24
hours with intermediate grinding. Phase pure powdered sample is made in to feed and seed rods.
The growth conditions were similar to TbFe0.5Mn0.5O3 except the growth rate. A growth rate of
3mm/hr is used for Tb0.5Sr0.5MnO3. Good quality single crystals are obtained in both case and the
single crystalline nature is confirmed through Laue photograph.
S04-P57
SrMoO4:Ho :Tm crystal as new active material for mid – IR laser
3+
3+
Dunaeva E.E.*, Ivleva L.I., Doroshenko M.E., Zverev P.G., Nekhoroshikh A.V., Osiko V.V.
A.M. Prokhorov General Physics Institute Russian Academy of Sciences,
Vavilov str., 38, Moscow 119991, Russia
Solid state lasers, which operate in the spectral region around 2 µm, have great market potential
for the use in LIDAR and gas sensing systems. Due to intense absorption by H2O these lasers can
have many practical applications in a medical treatment. Crystalline materials doped with Tm3+ and
Ho3+ ions for developing 2 µm laser are based on the 3F4 →3H6 optical transition of Tm3+ (1.9 µm)
and the 5I7 →5I8 transition of Ho3+ (2.1 µm). Tm3+ ions can also be used as a sensitizer to transfer an
absorbed pump energy to Ho3+ ions, so that high power commercial laser diodes at 790 nm can be
used to pump Tm3+/Ho3+ co-doped systems.
The tungstate and molybdate sheelite crystals doped with RE ions can combine good laser and
nonlinear-optical properties and can be effectively used for developing of compact lasers with
Raman self conversion. Recently it has been shown that SrMoO4 crystals exhibit high Raman gain
coefficient [1]. The SrMoO4 crystal has good chemical stability and moisture resistance. Sheelite
type structure of SrMoO4 crystal allows introducing RE ions in concentrations sufficient for laser
generation. The strongest Raman mode (887 cm-1) corresponds to the breathing oscillation of four
oxygen atoms. The development of SrMoO4 crystals doped with Tm3+/Ho3+ ions could provide the
oscillation at the main laser wavelength (1.9-2.1 µm) as well as at 2.22–2.6 µm and 2.77-3.38 µm
the first and second Stokes components.
In this work we have developed the growth technology of high optical quality SrMoO4 crystals
doped with Ho3+/Tm3+ ions by Czochralski method from the melt in the air. We have obtained the
concentration series of Ho3+:SrMoO4, Tm3+:SrMoO4 and SrMoO4 crystals co-doped with Tm3+
(7.9·1019 cm-3) and Ho3+ (8.0·1019 cm-3). Typical dimensions of the crystals were 15x12x70mm. The
SrMoO4 crystals were grown along the [100] crystallographic direction perpendicular to the optical
C axis, that is characterized by the maximal Raman scattering cross-section. Due to similar ionic
radius trivalent RE ions can replace Sr2+, but this requires special charge compensation. That is why
Ho3+/Tm3+ ions were added into the melt in the niobates form.
The spectroscopic investigations of Tm3+/Ho3+:SrMoO4 crystal have shown the absorption
cross section of Tm3+ ions at 790 nm is strongly anisotropic. It reaches 1.1·10-20 cm2 for σ-polarized
radiation, that is twice higher than that for π-polarized and higher than that in YAG and YLF
crystals. The polarized fluorescence spectra of Tm3+/Ho3+:SrMoO4 crystal were measured under
795 nm excitation at T=300K and T=77K. Laser oscillations for Tm3+/Ho3+:SrMoO4 pumped by
laser diode (790 nm) produced 1.6 mW output power at about 2 μm with an absorbed pump power
of 90 mW with slope efficiency of 3%. The optimization of crystal composition and improvement
of the cavity configuration could result in the increase of laser parameters. We believe, that
Tm3+/Ho3+:SrMoO4 crystal can be a perspective material for developing mid-IR lasers with selfRaman conversion of radiation inside the active medium.
References:
[1] Basiev T.T., Zverev P.G., Karasik A.Ya., Osiko V.V., Sobol A.A., Chunaev D.S., Journal of
Experimental and Theoretical Physics, 99 (2004) 934–941.
S04-P59
Structural properties and spinodal decomposition of bulk ternary
semiconductor compounds with oxygen in the anion sublattice
1
2
Semiconductor compounds with oxygen in the anion sublattice, such as CdO, ZnO, MgO, BeO
and their ternary alloys (CdZnO, BeZnO, MgZnO), attract a very high attention in the last years due
to wide perspectives for modern opto- (especial for green spectral region) and microelectronics [14]. However, their specific properties and tendency to phase separation (both composition
fluctuations and several crystal phase coexisting) produce many problems with reproducible
growth of materials, based on these ternaries compounds and, consequently, with application to
practice [5]. Additionally, there is a lack of experimental and theoretical works on structural
(including interatomic distances) and thermodynamic properties of these semiconductor alloys.
In the paper, we present the analysis of the structural (anion-cation, cation-cation and anionanion distances) and thermodynamic properties (mixing energy, interaction energy and phase
diagrams) of bulk wurtzite and zinc blende ZnxCd1-xO, ZnxBe1-xO and ZnxMg1-xO semiconductors
as a function of composition "x". Good agreement with the experimental data was demonstrated.
Temperature (K)
1400
Binodal
Spinodal
1200
1000
800
600
400
200
0
0.0
TC= 978.8 K @ x=0.43
0.2
0.4
0.6
0.8
Experimental data:
Brown J.J. and Hummel F.A., J.Electron.Soc. 111 (1964) 1052
Ishihara J. et al., Appl.Phys.Lett. 89 (2006) 091914
Gruber T. et al., Appl.Phys.Lett. 83 (2003) 3290
Singh A. et al., ECS J.Solid State Sci.Technol. 2 (2013) Q136
Chien K.F. et al., J.Cryst.Growth 378 (2013) 208
Bertram F. et al., Appl.Phys.Lett. 88 (2006) 061915
Jiang J. et al., Journal of Alloys and Compounds 547 (2013) 59
Shtepliuk I. et al., App.Surf.Science 276 (2013) 550
Sartel C. et al., J.Vac.Sci.Technol.A 29 (2011) 03A114
Ohashi T. et al., Jap.J.App.Phy. 46 (2007) 2516
1.0
CdO mole fraction in CdZnO
Figure 1. Phase diagrams of wurtzite CdZnO computed with the thermodynamic properties derived in this work. Solid
line is binodal curve and dash-dotted line is spinodal curve. Circles are experimental data (right): grey circles denote
unstable phase and black circles denote stable phase.
References:
[1] Lee D.-H., Kim S., Lee S. Y., Thin Solid Films 519 (2011) 4361
[2] Lange M., Dietrich C. P., Brachwitz K., Stölzel M., Lorenz M., and Grundmann M., Phys.Status Solidi
RRL 6 (2012) 31
[3] Jiang J., Zhu L. P., He H. P., Li Y., Guo Y. M., Cao L., Li Y. G., Wu K. W., Zhang L. Q., and Ye Z. Z.,
J. Appl. Phys. 112 (2012) 083513
[4] Özgür Ü., Alivov Y. I., Liu C., Teke A., Reshchikov M. A., Doan S., Avrutin V., Cho S.-J., and Morkoç
H., J. Appl. Phys. 98 (2005) 041301
[5] Venkatachalapathy V., Galeckas A., Trunk M., Zhang T., Azarov A., and Kuznetsov A. Yu., Phys. Rev.
B 83 (2011) 125315
S04-P60
Li2MoO4 crystal growth from solution activated by low-frequency vibrations
Andrey Sadovskiy*, Olga Barinova, Svetlana Kirsanova, Stanislav Belov, Ivan Ermochenkov, Marina
Zykova, Andrew Khomyakov, Elena Mozhevitina, Igor Avetissov
D.Mendeleyev University of Chemical Technology of Russia, Miusskaya pl.9, Moscow (Russia)
Molybdenum based crystals are known as effective materials for cryogenic phonon-scintillating
detectors and they are widely used for 100Mo 2β-decay investigations and dark matter search [1].
The most perspective detectors so called «active» detectors allow realizing the generation of rare
nuclear event and its registration in the same crystal. The crystal materials for these detectors have
basically a scheelite-type structure (CaMoO4, CdMoO4), and a high light yield at low temperature.
Unfortunately, all of them have long-lived radioactive isotopes (48Са,116Cd) entangles neutrinoless
2β-decay searches.
In [2] we have analyzed the properties of CZ-grown 50 mm diameter transparent Li2MoO4
crystals and showed the difference in Raman spectra for ||с oriented and c oriented crystals and the
absence of MoO42- complex distortions.
In this research we try to get ultra-low-background radioactive detector material based on
Li2MoO4 crystal grown from water solution. One of the main problems of solution growth
technique is a small growth rate. The Li2MoO4 solution is very complex and has large size
associates which decrease the solution viscosity and reduce the growth rate. In [3] it was
demonstrated that application of axial vibration control (AVC) technique could change a liquid
structure by destroying associates. We have grown Li2MoO4 crystals from AVC activated water
solution and investigated their spectral and physical properties in comparison with CZ-grown and
normally water grown crystals as well as a crystal purity. It was found out that AVC-crystals were
grown with the rate in 2 times higher comparing to normally grown crystals. The purity of AVC
grown crystals analyzed ICP-MS towards U and Th was <0.01 ppb and <0.05 ppb, correspondingly.
The AVC-grown crystals had structure (rocking curves) and spectral (transmission, Raman)
characteristics close or higher than the CZ-grown crystals.
The research was financially supported by the Ministry of Science and Education of Russia
grant N 14.577.21.0146.
References:
[1] V.B.Mikhailik, H.Kraus. J.Phys.D: Appl.Phys. 39 (2006) 1181-1191
[2] O.Barinova, S.Kirsanova, A. Sadovskiy,I. Avetissov J.Cryst.Growth 401c (2014) 853-856
[3] A.Sadovskiy, E. Sukhanova, S. Belov, V. Kostikov, M.Zykova, V. Artyshenko, E. Zharikov, I. Avetissov
J.Cryst.Growth 417 (2015) 16-24
S04-P63
Investigation of some key working parameters in a Kyropoulos process for
silicon using numerical modeling.
Nouri Ahmed *1, 2, Delannoy Yves 1, Lhomond Leslie 1, Chichignoud Guy 1,3, Helifa Bachir 2,
Lefkaier Ibn Khaldoun 2, Zaidat Kader 1
1
2
Univ. Grenoble Alpes, SIMAP, F-38000 Grenoble, France
LPM laboratory, Laghouat University, 3000Laghouat, Algeria
3
CNRS, SIMAP, F-38000 Grenoble, France
The Kyropoulos crystal growth technique can produce high quality bulk crystals for
applications requiring low dislocation density thanks to lower thermal gradients in the melt. Our
work investigates the growth of square shaped silicon ingots for photovoltaic applications using
Kyropoulos process. We present our numerical simulation of silicon ingots solidification in a
modified DSS furnace with three heating zones operating as a Kyropoulos machine. Due to the
square geometry of the crucible, 3D modeling was carried out to calculate the temperature
distribution as well as fluid dynamics and solidification. Experimental and numerical investigations
progressed in parallel to study the growth conditions. The obtained experimental results are
favorably in agreement with the simulation model results. We compare, in this work, different
Kyropoulos configurations and different operating parameters of heating distribution to highlight
the effects of these modifications on the final solidified crystal.
S04-P64
Effectivity of chemical vapor transport for ZnO single crystal growth based on
HCl vapors
Colibaba Gleb* 1,2, Shtepliuk Ivan3, Goncearenco Evgenii1, Inculet Ion1
1Moldova
State University, A. Mateevici 60, MD-2009, Chisinau, Moldova
Federal University, Kremlevskaya 18, 420008, Kazan, RF
3 Linkoping University, 581 83, Linkoping, Sweden
*
2Kazan
The thermodynamic analysis for use of HCl as a chemical vapor transport agent (TA) for ZnO single
crystals growth in the closed growth chambers is carried out in comparison with Cl2, H2 and CO. High density
of products for HCl+ZnO interaction, that is favorably for high quality of grown crystals, as well as low
temperature dependence of the product densities limiting the rate of ZnO mass transport are predicted. The
thermodynamic analysis for use of HCl+H2 and HCl+carbon mixtures is carried out and the possibility of
increase in the growth rate is shown (Fig. 1(a)).
The influence of the growth temperature in the range of 775-1050 °С, density of HCl/HCl+H2/HCl+C TA
and undercooling were investigated experimentally on the rate of ZnO mass transport. It is shown that the use
of hydrogen and C/CO as a TA for ZnO is limited by low structural perfection of the obtained crystals and their
destruction during a post-growth cooling because of a strong mechanical contact between grown materials
and walls of quartz growth chambers. The use of HCl with a high density up to several atm is favorable for the
growth of voids free crystals; however, it is limited by the low rate of mass transport. The use of HCl+H2 gas
mixture or HCl+C as a TA is useful for 950-1050 °С growth temperature range and also has following
advantages: (i) the increase of growth rate in 4-6 times up to 1 mm per day (Fig. 1(b)); (ii) reduction of the
growth nucleus density down to 1-3 cm-2; (iii) seeded growth of single crystals (having diameter up to 2 cm)
densely filling of the growth chamber volume; (iv) absence of the essential attachment effect and destruction of
crystals during a post-growth cooling and not typically low dislocation density down to 0-4 mm-2. The use of
HCl+C TA is more preferred and stable as it allow to avoid necessity of continuous supply of hydrogen to the
quartz growth chamber.
Figure 1. Temperature dependence of the pressure of products for HCl+H2+ZnO interaction (a) (loaded pressure of HCl
and H2 = 1 atm). Influence of the growth temperature on ZnO mass transport rate (b).
This work was supported by the Moldavian National grant No.14.819.02.14A, and partially by the Russian Government (agreement
No.02.A03.21.0002) to support the Program of Competitive Growth of Kazan Federal University among World’s Leading Academic
Centers.
S04-P66
Temperature dependent optical absorption of strontium titanate
Kok, Dirk Johannes 1*, Irmscher, Klaus1, Naumann, Martin1, Guguschev, Christo 1, Galazka, Zbigniew1 and
Uecker, Reinhard 1
1
Leibniz Institute for Crystal Growth, Max-Born-Str. 2, Berlin (Germany)
SrTiO3 is a prevalent epitaxy substrate for numerous oxide films and the only substrate crystal
for all known oxide based two dimensional free electron gas systems [1]. At present, the
performance of such epitaxial structures suffers from low quality of the available substrates which
are commercially grown by the flame fusion (Verneuil) method [2,3]. The most preferred growth
method for high-quality bulk oxide crystals is the Czochralski method. But in case of SrTiO3,
growth instabilities such as foot formation and spiraling make it impractical. These instabilities
indicate insufficient radiative heat transport through the crystal at high temperatures.
To investigate the temperature dependence of the radiative heat transport, the optical absorption
edge and the near infrared absorption of SrTiO3 were measured at temperatures from 4 K to 1703 K.
The absorption edge decreases from 3.27 eV at 4 K to 1.9 eV at 1703 K and is extrapolated to
approximately 1.3 eV at the melting point (2350 K). Because of free carrier absorption the
transmission in the near IR decreases rapidly above 1400 K. At 1673 K it is only about 50% of the
room temperature value. The free carriers are mainly generated by thermal excitation of electrons
over the band gap. The measured red shift of the optical absorption edge and the rising free carrier
absorption strongly narrow the spectral range of transmission and impede radiative heat transport.
To minimize problems associated with radiative heat transport through the growing crystal,
single crystal growth experiments were performed using the top-seeded solution growth method
(i.e. TiO2-rich melt) at temperatures below 1540°C [4]. High quality, cylindrical SrTiO3 crystals
were obtained with this method, with none of the instabilities characteristic of high temperature
growth evident.
Figure 1. Measured and extrapolated band gap of SrTiO3.
References:
[1] A. Ohtomo, D. A. Muller, J. L. Grazul, and H. Y. Hwang, Nature, 419 (2002) 378.
[2] J. Bednorz and H. Scheel, J. Cryst. Growth 41 (1977) 5.
[3] S. Thiel, C. W. Schneider, L. Fitting Kourkoutis, D. A. Muller, N. Reyren, A. D. Caviglia, S. Gariglio, J.M. Triscone, and J. Mannhart, Phys. Rev. Lett. 102 (2009) 046809.
[4] Guguschev, C.; Klimm, D.; Langhans, F.; Galazka, Z.; Kok, D.; Juda, U. & Uecker, R, Cryst.Eng.Com
16 (2014) 1735.
SESSION 5
Advance in Crystal Growth Technology
Numerical modeling and experimental validation of electromagnetical stirring in
unidirectional solidification of multicrystalline silicon
1
Negrila Radu Andrei1, Popescu Alexandra1 ,Vizman Daniel*1
Faculty of Physics, West University of Timisoara, Bd. V. Parvan 4, 300223, Timisoara, Romania
The quality of multicrystalline silicon grown by directional solidification (DS) method is
strongly related with the control of the impurities distribution in the mould. It is well known that
melt convection plays an important role in the impurities distribution. Therefore, a control of melt
convection will improve the quality and yield of the solidification process by influencing the
interface shape and dopant and impurities distribution in a beneficial way. For a better control of
the flow in the whole melt volume, we propose a stirring method (figure 1) based on the idea of a
combination between a static magnetic field B and an electrical current I, giving rise to an
electromagnetic force which has a significant melt stirring effect, even for small values of I and
B[1,2].
Figure 1. Schematic representation of the electromagnetic stirring method
In order to understand the basic features of the melt flow in a DS-like configuration under
electromagnetic stirring, an isothermal model experiment in a rectangular crucible filled with a
room temperature GaInSn melt and a corresponding time-dependent numerical model, were
developed. Experimental velocity profiles measured by Ultrasound Doppler Velocimetry confirmed
the flow structure obtained in the numerical simulations. A parametrical study for a range of I and B
values was performed, in the case of a symmetrical electrode positioning along the diagonal of the
free melt surface. The resulting flow structure was analyzed and described in terms of a vortex or a
poloidal recirculation domination and a transition between the two. A characteristic parameter was
defined to quantify the different flow structures. Through the use of scaling analysis, two
dimensionless numbers corresponding to the two Lorentz force components were identified and a
good correlation between their values, flow structure and maximal velocity was observed. This
correlation makes possible the prediction of the flow structure for any set of the system parameters I
and B and a characteristic crucible length. The same conclusions would hold for a silicon melt if the
dimensionless numbers are conserved by choosing different I and B in respect with the different
material constants. The main contribution of this idea is to provide some additional growth
parameters (like intensity of electrical current and position of the electrodes) easy to be adjusted in
order to control the melt flow and interface shape.
[1] D. Vizman, C. Tanasie, J. Cryst. Growth 372 (2013) 1-8
[2] R.A. Negrila, A. Popescu, D. Vizman, Eur. J. of Mechanics-B/Fluids 52 (2015) 147-159
Crystal Growth of Cd1-xZnxTe by the Traveling Heater Method in Microgravity on Board of
Foton-M4 Spacecraft
E. B. Borisenko1, N. N. Kolesnikov1, A. S. Senchenkov2, M. Fiederle3
1 Institute of Solid State Physics, Russian Academy of Sciences, Chernogolovka, Russia
2 Research and Development Institute for Launch Complexes, Moscow, Russia
3 Materials Science Center, University of Freiburg, Freiburg, Germany
The task of crystal growth of CdTe and Cd1-xZnxTe (CZT) bulk specimens is stipulated by needs in
high-resolution ionizing-radiation detectors. These crystals, especially the ternary solution doped
with 6-10 at.% Zn, are very efficient for performance even at room temperature, without cooling.
These materials are attractive due to their high atomic number, high specific resistivity associated
with low leakage current, wide band gap, which provide high resolution and long-term stability of
X-ray and gamma-ray detectors at room temperature. The purpose is to grow perfect bulk crystals,
with low density of structural defects and homogeneous stoichiometric content.
Using of the traveling heater method (THM) provides the solution-in-melt growth, which results in
purification from foreign impurities and more uniform composition than in the case of the
traditional Bridgman (HPVB) or High Pressure Vertical Zone Melting (HPVZM) growth. But more
than this, since a crystal is grown from solution in melt via Te liquid zone, the growing temperature
was lowered considerably as compared to the melt growth, which allowed the experiment on board
of the Foton-M4 spacecraft launched for two-month trip in space. Why we consider crystal growth
in microgravity advantageous as compared to the terrestrial THM growth? Structural defects,
structural and chemical heterogeneities, pores, grain boundaries appear due to gravitational
convection. In space, in microgravity, diffusion and convection are approached to stationary
processes far closer than at presence of the gravitational field.
The crystals grown on board of Foton-M4 spacecraft and under terrestrial conditions via THM are
considered in this study. The parameters of the crystal growth obtained from the diffusion and the
convection mixing models conform to optimal experimental parameters under microgravity
conditions [1].
A CZT feed and single crystalline CdTe seed were loaded in a quartz ampoule, the traveling Te-rich
liquid zone was installed. The solvent zone width was 26 mm, the estimated temperature on the
interface was  780 ºC. The pulling rate was 0.3 mm/h, by ~10 times lower than in the case of
HPVB or HPVZM. The grown crystals were 32 mm in diameter and  42-43 mm in length. Highresistant crystals were obtained upon growth from the Te-rich solution.
According to the X-ray diffraction data, the crystal grown in microgravity is a single crystal with a
cubic phase with sphalerite lattice, a = 6.458Å, which coincides precisely with the calculated unit
cell parameter for this composition. The measured IR transmission reaches ~70%. The measured
Vickers microhardness HV under load 50 g is 640 MPa for the terrestrial crystal and 540 MPa for
the crystal grown in Space. Spread of the data for is about 6% for the former crystal, and less than
2% for the latter crystal.
We can conclude that the THM growth of CZT in microgravity results in production of the crystals
with homogeneous composition and in improvement of structural perfection as compared to the
crystals grown under terrestrial conditions. Consequently, THM growth in microgravity has a
positive effect on many properties of these crystals.
References
1. A.S. Senchenkov, M. Fiederle, and N.N. Kolesnikov, IAC-14-A2.4.7.
Modified Bridgman technique for growing Sb-based binary compounds
Pillaca Mirtha*1, Miller Wolfram2, Cocivera Viviane1, Maletin Tamara1, Gille Peter1
1
Department of Earth and Environmental Sciences, Crystallography Section, Ludwig‐Maximilians‐Universität München, Theresienstrase 41, 80333 München (Germany) 2
Leibniz Institute for Crystal Growth (IKZ), Max‐Born‐Str. 2, 12489 Berlin (Germany) *email: [email protected]
Many binary intermetallic compounds cannot be crystallized from congruent melts but have to
be grown below their specific peritectic temperature. E.g. FeSb2 and CoSb3 which are considered
interesting materials for thermoelectric applications can only be grown from Sb-rich solutions
containing more than 90 at. % Sb. Moreover, due to the relatively high Sb vapor pressure crystal
growth has to be carried out in closed ampoules, e.g. using the Bridgman method from a hightemperature solution. In vertical Bridgman growth buoyancy-driven convection is very weak
because of the vertically stable thermal conditions. Rotation of the ampoule increases the
convection but numerical simulations show that this not is enough to evoke a sufficient mixing in
the vicinity of the interface. Strong mixing is mandatory in order to remove the rejected Sb excess
from the phase boundary of the growing crystal. Without sufficient mixing second-phase inclusions
have been found in the crystal grown.
Crystals of both FeSb2 and CoSb3 grown by the vertical Bridgman method exhibit a high density
of Sb inclusions, even with extremely low growth rates of less than 1 mm/d. Three-dimensional
calculations of melt convection by employing the commercial software ANSYS-cfx show that a
much better mixing is achieved by tilting the Bridgman furnace. Computations have been
performed for a tilting angle of 75° with respect to the axis of gravity. Now, there is a temperature
variation in horizontal direction, which causes a Rayleigh-Benard instability and hence a
convection. Additional rotation of the inclined ampoule adds a forced convection resulting in a
time-dependent behaviour of the melt flow. This provides an efficient transport all along the
interface.
Experiments using this Inclined Rotary Bridgman technique resulted in single-phase ingots of
FeSb2 and CoSb3.
Experimental evidence that a high electric field acts as an efficient external parameter during
crystalline growth of bulk oxide
R. Haumont1,2, P. Hicher1, R. Saint-Martin1, X. Mininger3, P. Berthet1
1
Equipe Synthèse, Propriétés et Modélisation des Matériaux, ICMMO, CNRS-UMR8182,
Université Paris Sud, 15 rue Georges Clémenceau, 91405 Orsay Cedex, France
2
Laboratoire Structures, Propriétés et Modélisation des Solides, CNRS-UMR8580, Ecole Centrale
Paris, Grande Voie des Vignes, 92295, Chatenay-Malabry Cedex, France
3
Laboratoire de Génie Electrique de Paris, SUPELEC, CNRS-UMR 8507; Université Paris Sud,
11 rue Joliot Curie, 91192 Gif-sur-Yvette
The aim of the talk is to present a new way to design bulk functional oxide: a new crystal growth
device, in which a high static external electric voltage (up to 14 kV) was added to a floating zone
method. Our first experiments show that the application of such an electric field acts like an
external force, introducing a pressure effect which is in direct competition with temperature in the
solid/liquid thermodynamic equilibrium. High electric fields could therefore be an additional
parameter in crystal growth, opening original routes to the synthesis of new materials.
ECCG5-2015 Bologna Italy
High-pressure and ambient gas effect on the optical floating zone crystal growth
of novel oxide and intermetallic compounds
Paul Sass*, Robert Schöndube
ScIDre GmbH –Scientific Instruments Dresden, Großenhainer Str, 101, 01127 Dresden (Germany)
Floating zone (FZ) techniques enable the growth of surpassing quality single crystals. The
feasibility to control and to enhance parameters like growth atmosphere and temperature in a wide
range during the FZ growth with optical radiation heating leads to the creation of heretofore
unknown compounds with striking properties. Various novel oxide and intermetallic phases with
complex behavior have been successfully grown with optical FZ methods. We illuminate the
potentials of high pressures and different gases for the FZ crystal growth and place particular
emphasis on strongly correlated materials.
During the FZ growth process of intermetallic compounds, high-purity protective gases like
argon are used to avoid reactions with the melt. Due to their low partial pressure in these
atmospheres, volatile elements and constituents with low melting and boiling points can evaporate
from the molten zone. Applying low gas pressures down to vacuum conditions can stimulate the
volatilization of impurity elements and lead to melt purification during the growth process.
However, the selective evaporation is normally an undesired phenomenon because it shifts the
stoichiometry of the melt and the growing crystal. High-pressure atmospheres of inert gases
substantially restrain the evaporation from the molten zone and enable the creation of intermetallic
phases which would remain elusive under low ambient pressures. Elevated gas pressures are also
used in the floating zone growth of oxides to reduce evaporation losses and to maintain the
stoichiometry of the molten zone. Furthermore, specifically the O2 partial pressure interacts in
subtle way with the thermodynamic stability of cationic valence states at melting temperature.
Depending on the intended process, this interaction might lead to the necessity of elevated pressures
of inert gases, precise gas mixtures or generally a well-controlled O2 partial pressure during the
growth process. On the other hand, elevated oxygen pressure has been proved to affect directly the
thermodynamic equilibrium and the solidification behavior of oxidic compounds. For some
materials, which melt incongruently in air or at low and normal pressure, congruent melting can be
achieved with significantly increased O2 pressure. The oxygen diffusion between the melting zone,
the crystal and the atmosphere can be controlled by applying a wide range of ambient O2 pressures
during the growth process. Thus, the O2 partial pressure affects not only the solidification mode of
oxides but also the composition, homogeneity and physical properties of the crystals themselves.
In recent times, floating zone crystal growth with ambient gas pressures > 15 MPa becomes
feasible. We introduce and discuss several novel applications of high pressure and their advantages
for the growth process.
Growth of Shaped Oxide Eutectics by the EFG Technique
Stryukov Dmitry*, Shikunova Irina, Kurlov Vladimir
Institute of Solid State Physics Russian Academy of Sciences,
2 Academician Ossipyan str., 142432 Chernogolovka, Moscow District, Russia
Directionally solidified eutectic ceramic oxides have a high hardness, melting point, very good
thermal conductivity, tensile strength and thermal shock resistance. They are very interesting and
attractive as structural materials for high-technology applications (aeronautics, aerospace, power
generator technologies etc.), first of all, because of their inherent high strength, high oxidation and
creep resistance at temperatures up to 1600ºC.
The optimization of standard solidification technologies and development of new techniques are
actively pursued in order to increase the dimensions of ceramics, improve the quality, homogeneity
and stability of microstructure, reduce the cost of material, and obtain complex shapes during the
solidification process.
Oxide eutectics of any predetermined cross-section, constant along the crystal length (rods of
various cross-sections, ribbons, tubes, fibers, etc.), have been grown by the EFG technique, Fig. 1.
The method has been used to obtain a variety of the shaped binary eutectics, such as Al2O3Y3Al5O12, Al2O3-Er3Al5O12, Al2O3-GdAlO3, and one ternary eutectic system Al2O3-ZrO2(Y2O3).
Mechanical properties and microstructure of various oxide eutectics (Fig. 2) depending on
growth rates were investigated. The garnet eutectics have “chinese script” structure. The specific
dimensions of phases corresponded to Hunt-Jackson law at growth rates from 30 to 300 mm per
hour. Some perovskite eutectics contain rod-like structure with single crystalline phases, which
makes them attractive for photonic applications.
Figure 1. Shaped Al2O3-Er3Al5O12 eutectics grown by the EFG method
Figure 2. Microstructure of Al2O3-Y3Al5O12 (at the left), Al2O3-ZrO2(Y2O3) (at the middle) and Al2O3GdAlO3 (at the right) eutectics grown by the EFG method
High-pressure crystallization of organic compounds in a diamond-anvil cell
Michał Andrzejewski1, Andrzej Katrusiak1
1
Department of Materials Chemistry, Adam Mickiewicz University, Umultowska 89b,61-614 Poznan (Poland)
Diamond-anvil cell (DAC) is a simple apparatus which provide possibility to study materials
under extreme pressure conditions [1,2]. Thus, utilizing Xrays diffractometry, it is easy to observe
structural changes in a single crystal. This is well known that pressure may induce phase transitions,
resulting in new crystal forms. Hence, it is a perfect method for exploring phase diagrams and
polymorphism. Moreover, there are many examples of significant geometric, conformational and
packing changes in a crystal which are associated with physical properties like negative
compressibility, spin cross-over, amorphisation, molecular conduction [3].
High-pressure crystallization in a DAC (both isochoric and isothermal) is a unique method for
controlling a single crystal growth (Figure 1). It is crucial to select a proper solvent which is also
pressure transmitting medium. Organic compounds, due to their low melting temperature, are
effortless in crystallization and a sample may be prepared usually within few hours.
Figure 1. An isochoric growth of a single crystal in a diamond-anvil cell and the cross section of a DAC with two
diamonds squeezing a sample in a metal gasket.
References:
[1] Katrusiak A., Acta Cryst., A64 (2008) 135-148.
[2] Merrill L., Bassett W. A., Rev. Sci. Instrum. 45, (1974), 290-294.
[3] Tidey P.J., Wong H.L.S., Schroder M., Blake A.J., Coord. Chem. Rev. 277-278, (2014), 187-207.
Direct measurement of the crystallization pressure at the pore scale
Julie Desarnaud1*, Daniel Bonn1, Noushine Shahidzadeh1
University of Amsterdam , Institute of Physics, Science Park 904, 1098 XH Amsterdam (The Nederlands)
The precipitation of salt minerals in confinement (e.g. pores in porous media) is known to severely
damage buildings, to be responsible for the weathering of rocks and to reduce the permeability in
oil reservoirs. In all of these cases, crystal growth occurs within the pore spaces of the material,
inducing mechanical stresses on the scale of the individual grains or pores. A condition for damage
to occur is that the crystal continues to grow even in confinement, and that the resulting stress
damages the rock or stone.
Arguments explaining that growing crystals can exert a pressure have been given for more than 150
years; From the first experiments of Lavalle in 1853 and Becker et al 1905, it has been concluded
that a crystal can grow under external pressure1. The authors argued that a crystal surface under
pressure could grow and overcome the external forces resisting growth provided the surface is in
contact with supersaturated solution1. Later, Correns2 gave the first equation for the crystallization
pressure and its relation with the supersaturation , which was corrected subsequently by other
authors 3.
However, different experimental results for different salts published in the literature 4,5 open the
debate on the mechanism involved in the development of such a pressure especially as according to
both Riecke’s principle and crystal growth theories, a mechanically constrained crystal because of
its higher solubility should dissolve4 rather than exert a pressure. Consequently, for understanding
the deterioration mechanism of crystal growth, a direct measurement of the crystallization pressure
exerted by crystals growing in a confined environment is needed.
We present a novel method that we have developed in order to directly measure the crystallization
pressure exerted by a growing microcrystal in a confined geometry under controlled environmental
conditions6. This new method allows us to follow simultaneously the nucleation and spontaneous
growth of the crystal from the salt solution and to measure the subsequent pressure developed at the
pore scale. The important role played by the wetting properties and the nature of the salt on the
development of a pressure during the growth will be discussed
References:
[1]. S.Taber. The growth of crystals under external pressure, American Journal of Science V,41, (1916)
[2]. 532-556.
[3]. CW.Correns , Growth and dissolution of crystals under linear pressure, Discuss Faraday Soc.5, (1949)
267-271.
[4]. R.J.Flatt, M.Steiger, G.W.Scherer, A commented translation of the paper by C.W.Correns and W.Steiborn
on crystallization pressure, Envion. Geol. 52 (2007) 187-203.
[5]. J.Desarnaud et al. , Growth and Dissolution of Crystal under Load: New Experimental Results on KCl ,
Crystal growth and design 13 (20130, 1067-1074,
[6]. K.Sekine, A.Okamoto, K.Hayashi, In situ observation of the crystallization pressure induced by halite
crystal growth in a microfluidic channel. American Mineralogist, 96, (2011) 112-119.
[7]. J.Desarnaud, D.Bonn, N.Shahidzadeh, Direct measurement of the crystallization pressure at the pore
scale, submitted
POSTER
S05-P01
Isostructural phase transition of 2,4,5-triiodoimidazole at high pressure
Kacper Rajewski, Michał Andrzejewski, Andrzej Katrusiak.
Adam Mickiewicz University, Department of Materials Chemistry, Unultowska 89b 61-614 Poznań
Switchable polarization of NH•••N hydrogen bonds remains in a great interest of crystallographers
due to their ferroelectric properties. This effect has been recently reported for dabco salts and
halobenzimidazoles [2]. Halogen interactions are kind of electrostatic interaction that can be as
strong as hydrogen bonds and may force different molecules arrangement in space. What is more
X•••X interactions can significantly shorten NH•••N bond length and allow proton transfer along
hydrogen bond chains. We have recently reported structural studies of several imidazole
haloderivatives [2]. 2,4,5-Triiodoimidazole (TIIm) at ambient conditions crystallize in P21/a space
group with Z’=3. High pressure experiments led to a new 2,4,5-triiodoimidazole ring arrangement.
Phase transition is isostructural and nondestructive.
Figure 1. (a) structure of TIIm at ambient conditions, (b) high‐pressure structure of new phase References:
[1] S. Horiuchi, F. Kagawa, K. Hatahara, K. Kobayashi, R. Kumai, Y.i Murakami Y. Tokura, Above-room-temperature
ferroelectricity and antiferroelectricity in benzimidazoles, 2012, Nature Communications 3, Article number: 1308.
[2] M. Andrzejewski, J. Marciniak, K. Rajewski, A. Katrusiak, Halogen and hydrogen bonds architectures in
switchable chains of di- and trihaloimidazoles, 2015, Cryst. Growth Des. 15 1658-1665
S05-P02
pH specific single crystal growth of N-H+…Cl- influenced [ZnCl4]- [R]+ hybrid
materials of 3D to 2D lattice dimensionality by organic variant:
Microscopy, optical Eg and PL properties.
Dinesh Jasrotia1*, Sanjay K. Verma1, B. Sridhar2 and Ajit Kumar1
1
Department of physics ,Govt. Gandhi Memorial Science College, Jammu-180016, Jammu and Kashmir India.
2
Laboratory of X-Ray Crystallography, CSIR-Indian Institute of Chemical Technology Hyderabad, India.
Single crystal growth process and detailed physicochemical characterization such as XRD,
Structure stability with non-covalent interactions, UV-Vis spectroscopy, FESEM image analysis,
lattice dimensionality (3D-2D) and luminescence property correlations were used in interweaving
the design of two inorganic-organic hybrid materials. Single tube diffusion method in silica gel
medium has been used to establish the conducive conditions for single crystal growth of bis(2methylpyridine)tetrachlorozincate [MPCZ]. Gel medium with different pH were tried but
diffraction quality single crystals were obtained at 5 pH of sodium metasilicate gel, ZnCl2 as lower
reactant of 0.5M, 2-methylpyridine as upper reactant with conc. of 1M and Gel column length of 12
cm. Single crystal growth of bis(2-amino-5-chloropyridine)tetrachlorozincate [ACPCZ] has been
performed by solution growth (SG) and slow cooling (SC) process by adding zinc chloride
[0.092g], 2-Amino-5-chloropyridine [0.102g] and 5ml of HCl. Complete dissolution is achieved in
10 hours at 100oc and the solution was cooled slowly in 48 hours which results good quality single
crystals of hybrid material.
Single crystal X-ray diffraction structure analysis has been performed for MPCZ and ACPCZ
hybrid compounds which depict that the N-H+…Cl- hydrogen interactions held the inorganic and
organic moieties together into hybrid composite. In MPCZ hybrid material, organic moiety form 3D
spreader shape pattern [6.89 x 4.44 x 4.15Å] and the inorganic moiety link the train of spreaders
along ac-plane whereas the change in organic in ACPCZ moiety has 2D shear grade pattern of
inorganic-organic components along b-axis with steepness grade of 1.29 and angle of inclination of
49.5o. FESEM image of MPCZ depicts that the surface of the hybrid materials filled with spherical
granules and the shape descriptor indicates the average granular size of 28nm and circularity of
0.964 whereas the image of ACPCZ shows variation in spatial parameters of average granular size
of 60nm due to alteration of organic derivative from 2-methylpyridine to 2-amino-5-chloropyridine.
The change in optical energy direct band gap value from 3.01eV for MPCZ to 3.42eV for ACPCZ
indicates the role of organic compounds in optical properties of hybrid materials. The
photoluminescence emission spectra is observed in the wavelength range of 384 to 590 nm with
maximum peak intensity of 9.66 a.u. at 438 nm for MPCZ and 388 to 600 nm with maximum peak
intensity of 9.91 a.u. at 442 nm for ACPCZ, indicate the emission spectra lies in visible range.
Fig.: Photoluminescence and physicochemical depiction of [ZnCl4]- [R]+ hybrids.
S05-P04
Heptadecane and Gallium Crystallization in Hydrodynamic Czochralski Model
Berdnikov Vladimir1, Prostomolotov Anatoly2*, Verezub Nataliya2, Vinokurov Victor1
1
Institute of Thermophysics of Siberian Branch of Russian Academy of Sciences, Lavrentev ave. 1, Novosibirsk (Russia)
2
Institute for Problems in Mechanics of Russian Academy of Sciences, Vernadskogo ave. 101(1), Moscow (Russia)
This work presents a development of our investigations made without crystallization process by
using ethanol as the modeling medium [1]. Processes of convective heat transfer and crystallization
were studied on basis of the simplified, but the common calculation-experimental Czochralski
model by using the two materials having the room melting temperatures: 1 – heptadecane having a
low thermal conductivity and 2 – gallium having a high its value. The transparency of heptadecane
melt (with melting temperature at 295 K) allowed to visualize a melt stream and geometry of its
crystallized mass in this experiment and to provide the data for a verification of the corresponding
calculation model. The results of such verification were successful and they are shown in Fig. 1.
Numerical modeling has allowed to study parametrically the heat fluxes on the cooled disc and
a convexity of melt-crystal interface for both these substances in the modes of thermal and mixed
convection (i.e. with an additional crystal rotation). The means of effective influence on meltcrystal interface based on the controlled change of crystal rotation rate during growth process [2]
have been analyzed.
1
1
2
2
b
а
1
1
2
2
d
c
Figure 1. Crystallization of heptadecane (1 – cooled disk, 2 – crystalline portion) during
thermal convection (a,b) and at joint action of thermal convection and crystal rotation
(c,d): a,c – streamlines (left of the axis) and temperature contours [K] (right of the axis);
b,d – photo of crystalline portion of this material (dark area).
References:
[1] Berdnikov V.S., Prostomolotov A.I., Verezub N.A., J. of Crystal Growth, 401 (2014) 106.
[2] Verezub N.A., Nutsubidze M.N., Prostomolotov A.I., Fluid Dynamics, 30-4 (1995) 510.
S05-P06
Growth of large size YAG:Ce crystals with homogenous distribution of Ce3+ ions
by HDC method for WLED application
Nizhankovskyi S.V.*1, Tan’ko A.V.1, Savin Yu.N. 1
1
Due to the high temperature stability and efficiency of luminescence, high thermal conductivity
YAG:Ce garnet crystals have promising application in high-power white light-emitting diodes
(WLED) as luminescent converters of blue light emitted by InGaN LED (460 nm). One of the most
effective methods for growing of large size garnet crystals is horizontal directional crystallisation
method (HDC). This method is a variation of zone melting, and allows to use its advantages
associated with the ability to control the composition of the ingot along its length [1].
The aim of this work was to specify the conditions for growing large-size YAG:Ce crystals with
a uniform distribution of the activator (Се3+ ions) along of crystal length and optimize their lightconverting characteristics. It is found that the distribution of the activator in the crystal greatly
depends on its distribution in the starting material, the ratio of the melt zone to the length of the
crystal, the convective conditions in the melt, and other factors. It is shown that the use of a gradient
doping of starting material allows one to obtain YAG:Ce crystals (up to 100×150×25 mm3) with
high homogeneity of Ce3+ ion distribution (ΔC <8-10%), high optical and luminescent properties
(Fig. 1a, b). Investigation of light-converting characteristics of YAG:Ce crystalline plates made of
grown crystals showed that the color emission characteristics depends not only on the concentration
of ions of Ce3+, but also on surface morphology of the plates (Fig. 1c). As a result of parameters
optimization we showed that the of the possibility of creating WLED with YAG:Ce crystalline
plates with correlated color temperature of ТCC ≈ 5000-6000 K and color rendering index CRI ≈6070.
Figure 1. (a)-YAG:Ce crystal grown by HDC method ; (b) -YAG:Ce crystalline plates;
(c) – Color characteristics of LED with YAG:Ce crystalline plate.
References:
[1] S.V. Nizhankovskiy, E.V. Krivonosov, V.V. Baranov Inorganic materials, V.48, (2012), pp. 1111-1114.
S05-P07
The approach for reconstruction of GaSb:Te space crystal growing
Prostomolotov Anatoly1*, Verezub Nataliya1, Voloshin Alexey2, Nishinaga Tatau3
1
Institute for Problems in Mechanics of Russian Academy of Sciences, 101-1 Vernadskogo ave., Moscow (Russia)
2
Institute of Crystallography of Russian Academy of Sciences, 59 Leninskii ave., Moscow (Russia)
3
Department of Electronic Engineering of University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo (Japan)
Quantitative X-ray topography of GaSb:Te crystal, grown during chinese unmanned space
experiment [1] has showed a high structural perfection in its greater area, which corresponds to the
crystallization of a rounded interface. At the same time, the defects in the field of a facet growth
have been revealed after some time of the crystallization onset. The control of parameters during the
growth process was absent. It was a reason for a reconstruction of the crystal growth history using a
two-dimensional map of the measured Te concentrations in the crystal and mathematical modeling
of the growth process, and taking into account of possible factors that influenced on the growth
crystal characteristics [2]. The work has developed the mathematical models of different levels of
complexity for calculating the crystallization process of GaSb:Te (from semi-analytic and 2Dhydrodynamic, describing a convective heat and mass transfer in the melt [3] to the conjugate
thermal models that calculate the crystallization process in the real heating conditions and geometry
of ampoule assembly).
An applicability of analytical models (Barton Prima-Slichter – BPS and Ostrogorsky-Muller –
OM) was analysed in comparison with 2D-modeling of convective impurity transport. It gave a
possibility to consider BPS-model as a more accurate one, as well as offer its formula expressions
for highly elongated melt areas and large velocities. It was shown the non-monotonic variation of
macro-inhomogeneity impurity distribution on the crystallization interface (CI) upon the Grashoff
number [3].
The influence of the heating conditions and the ampoule velocity on the crystallization rate and
CI shape was investigated. It was studied the influence of main factors that influenced on the crystal
quality: on Keff values, facet growth and transverse impurity inhomogeneity on the CI. The main
factors were the thermal conditions (the values of the axial and radial temperature gradients, cooling
rate), and the transverse ampoule size. It may be noted that the space experiment was carried out in
conditions close to optimal. The realized values of the crystal growth rate have provided an
acceptable level of radial inhomogeneity and temperature gradient – the relatively small size of the
facet growth. The small diameter of the growth ampoule has provided a large "margin of safety" in
relation of a convective influence on the heat transfer. The only deficiency of this experiment was
the facet growth some time after the onset of crystallization. It was shown that the moment of the
additional free surface formation near CI corresponds to the contact of the melt with the graphite
insert. The non-coaxial contact relatively to the ampoule may be as a possible reason of a thermal
asymmetry and a growth process disturbance. The facet growth was caused by such sharp change of
the thermal conditions that led to the stronger thermocapillary effect and dramatically increasing the
convection velocity. For Keff(Vmax) dependence it corresponds to a shift in the field of sharp change
of Keff for the small variations of thermal parameters. It explains the observed features of the
impurity distribution in the field of facet growth.
References:
[1] Ge P., Nishinaga T., Huo C. et al., Microgravity Q., 3 2-4 (1993) 161.
[2] Voloshin A.E., Nishinaga T., Ge P., Huo C., J. of Crystal Growth, 234 (2002) 12
[3] Prostomolotov A.I., Verezub N.A., Voloshin A.E., J. of Crystal Growth, 401 (2014) 111.
S05-P08
Influence of melt transparency on critical growth rate of sapphire
V.V. Baranov*1, S.V. Nizhankovskyi 1
1
The main factor which limits the rate of crystal growth is morphological instability (MI) of the
crystallization front. One of the problems arising at investigation of the conditions of the occurrence
of MI at the growth of high-temperature semitransparent sapphire is the necessity to take into
account radiative supercooling of the melt in the vicinity of the crystallization front. This requires
knowledge of the optical properties of the melt. In the present work there were established the
degree of melt transparency in the vicinity of the crystallization front, as well as the influence of the
melt transparency and the content of impurities on the critical growth rate of sapphire and
Ti:sapphire crystals. The study was realized on the base of the analysis of the MI instability taking
into account radiative heat transfer [1] and experimental data on the conditions of the growth of
sapphire by the method of horizontally directed crystallization. The values of the absorption
coefficients in the melt in the vicinity of the crystallization front (averaged according to Planck and
Rosseland) were found to be  LP ≈13.5 сm-1 and  LR ≈ 20 сm-1, respectively. The value of the melt
supercooling caused by radiative heat transfer is ≈ 0.3-0.5 оС (Figure 1). It is shown that the
critical growth rate of sapphire is close to the limiting case of the growth of absolutely pure
sapphire (Сim = 0) (Figure 2, curves 2, 3). At the growth of Ti:sapphire with a high content of
impurities MI is defined by the concentration supercooling of the melt, but the critical crystal
growth rate also noticeably depends on the melt transparency (Figure 2, curves 1 ).
2324
T,K
2324
2322
S
L
1
2320
2320
2
 0. 004
4

0. 003
3
z,mm
 0. 002
2
 0. 001
1
0. 001
1
0. 002
2
Figure 1 Temperature distribution in the vicinity of the crystallization front at the growth of
sapphire - (1) and Ti:sapphire ( Ti concentration in the melt is 1 mol. % ) - (2) .
Figure 2 Critical growth rate of sapphire, Сim=0. 05 mol. % - (2), Сim= 0 mol. % - (3) and
Ti:sapphire (CTi=1 mol. %) - (1) depending on the value of the absorption coefficient in the melt
averaged according to Planck (a) and Rosseland (b).
References:
[1]. Yuferev V.S., Chvoj Z., Kolesnikova E.N. // Journal of Crystal Growth. 1991. V.108 P. 367.
S05-P09
Growth of high optical quality ZnS single crystals by solid phase
recrystallization technique at barothermal treatment
Eugeni Gavrishuk1, Vladimir Ikonnikov1*, Tatyana Kotereva1,Vladimir Pimenov1,
Dmitry Savin1, Pavel Yunin2, Elena Mozhevitina3, Roman Avetisov3
1
G.G. Devyatykh Institute of Chemistry of High-Purity Substances RAS, 49 Troponina St., Nizhny Novgorod (Russia)
2
Institute for Physics of Microstructures RAS, Nizhny Novgorod (Russia),
3
D. Mendeleyev University of Chemical Technology of Russia, Miusskaya pl.9, Moscow (Russia)
A large number of techniques is used for the growth of extra pure and high quality ZnS crystals
which is very attractive as a laser material and component phosphors. The melt growth techniques
do not allow producing extra pure ZnS, because of high contaminating action of setup materials at
high temperatures. The chemical transport reactions technique is conducted at lower temperatures,
but it contaminates the growing crystals by additional reagents. ZnS single crystals growing from
vapor demonstrate an inconstant stoichiometry.
In this situation a solid phase recrystallization (SPR) technique is regarded as a promising
alternative for growing crystals of high purity and structural perfection [1]. It was successfully used
to grow ZnSe, and ZnS single crystals of at ambient pressure close to atmospheric. The main
disadvantages of this SPR technique is the formation of twins and the process duration, which
amount up to 20 days at of 900 to 1100°C temperatures. It is difficult to apply higher temperatures
due to zinc chalcogenides sublimation.
An implementation of the SPR technique under isostatic pressure makes it possible to increase
the temperature to 1300°C and to reduce the process time up to 1-2 days.
In the research we conducted a solid phase recrystallization of polycrystalline ZnS under
barothermal exposure (PAr = 90-200 MPa, T=1000-1200°C, t=22-44 hours). The polycrystalline
ZnS with 10 microns average grain size produced by CVD technique was used as a raw material
[2]. According to XRD the obtained ZnS samples after the barothermal processing composed of
individual single crystals with a size of up to 15×15×6 mm. Nearby single crystals had at is very
different orientation (parallel to the surface of various atomic planes), and slightly different
orientation (disoriented relative to each other only a few degrees). The values of the rocking curve
FMWH in the /2-scan for various single crystals varied in 0.04° to 0.7° range. The crystal's
transmission in 0.35-14 microns range was close to the theoretical value.
The purity as-grown crystals examined by ICP-MS technique was <10-4 wt.%. The main
impurities (Fe,Cu) occurred from the gas-static setup. We reduced their concentrations in several
times by placing ZnS samples in a tungsten foil container.
The obtained results offer the challenge for growing ZnS and ZnSe perfect single crystal by a
solid phase recrystallization under barothermal impact.
The research was supported by the Russian Science Foundation grant N 15-13-10028
References:
[1] R. Triboulet. Cryst. Res. Technol. 38(3-5) (2003) 215 – 224
[2] E. M. Gavrishchuk, V. B. Ikonnikov, D. V. Savin. Inorganic Materials 50(3) (2014) 222-227
S05-P10
Sapphire Shaped Crystals for Medicine
Kurlov Vladimir, Shikunova Irina*, Stryukov Dmitry
Institute of Solid State Physics (ISSP), 2 Academician Ossipyan str., 142432, Chernogolovka (Russia)
Excellent combination of mechanical and optical properties of sapphire together with chemical inertness
and biocompatibility makes it an attractive structural material for medicine. We have developed new medical
instruments and devices for laser photodynamic therapy and thermal therapy, laser surgery, fluorescent
diagnostics, and cryosurgery based on sapphire crystals of various shapes with capillary channels in their
volume grown by the EFG technique.
Sapphire needle capillaries were developed as new laser waveguide introducers for delivery radiation
into a tumor during interstitial laser photodynamic therapy, thermotherapy, and ablation of tumors. These
needles allow one to increase the irradiation volume substantially, to obtain an optimal light or temperature
distribution (Fig. 1) to simplify the design, and to eliminate a system for cooling the device.
Sapphire scalpels with simultaneous incision and rapid real-time feedback analysis for on-line
fluorescent diagnostics of tissues during surgery during surgical operation have been developed. The
principle of the new system is based on the use of isolated capillary channels in the volume of the sapphire
scalpel for introducing of quartz waveguides, Fig. 2. One of the waveguides is used for delivering the laser
radiation directly to the narrow region of the cutting edge and local excitation of photoluminescence.
Another one is used for catching and transfer of photoluminescence to spectrometer.
The system for removal of brain tumors based on a sapphire multi-channel probe with demarcation of
borders of a tumor by fluorescent diagnostics with simultaneous coagulation and aspiration was developed,
Fig. 3. It carries out simultaneous laser coagulation for a hemostasis, tumor aspiration via the through
channel of a sapphire probe, and also makes local optical measurements of properties of brain tissue for more
exact and full removal of malignant tissue.
Sapphire cryocooler-ligthguide for simultaneous or sequential laser therapy and cryoablation have
been developed, Fig. 4. This allows to create the desired temperature gradient and to realize the fluorescent
diagnostics of biological tissue during or after cryotherapy.
Figure 1. The geometry of light field in sapphire needle (OD 1.2 mm, ID 0.5 mm) combined with quartz
fiber.
Figure 2. The sapphire blade with capillary channels of 0.5 mm diameter.
Figure 3. Sapphire multichannel probe for neurosurgery
Figure 4. Сryocooler-lightguide
S05-P11
Salt stains from evaporating droplets
Noushine Shahidzadeh*1, Julie Desarnaud1, Marc Prat2, Daniel Bonn1
1
University of Amsterdam, Institute of Physics,WZI, Science Park 904, 1098 XH Amsterdam (The Netherlands)
2
Université de Toulouse, INPT, UPS, IMFT, Toulouse (Franc)
In many applications such as the purification of pharmaceuticals, de-icing of airplanes, inkjet
printing and coating applications, a phase change happens within the drop because of solvent
evaporation, temperature changes or chemical reactions, which consequently lead to liquid to solid
transitions in the droplets. Although the deposition pattern has been much studied for evaporating
droplets of colloidal suspensions, very few studies exist of evaporating salt solutions, in spite of the
fact that in many practical situations water contains dissolved salts, and that the much-studied
colloidal systems are usually considered to be models for atomic systems.
We therefore investigate the crystallization and resulting deposition patterns at microscale for drops
of aqueous solutions of two different salts (NaCl and CaSO4) that evaporate on surfaces with
different wettability and thermal conductivity. These salts are selected firstly because of their
importance in many natural and industrial processes and secondly because they have different
crystalline structures and precipitation pathways. Our results show that crystallization patterns of
evaporating salt solutions are different from the stains reported for evaporating colloidal
suspensions. This happens because during the solvent evaporation, the salts crystallize and grow.
The resulting patterns of salt crystal stains are found to be predominantly controlled by the wetting
properties of the crystal as well as the pathway of nucleation and growth, and are independent of the
evaporation rate and thermal conductivity of the substrates.
Figure 1. Phase-contrast micrographs of the growth of CaSO4 polymorphs at the contact line for
various contact angles θ of the droplet with the glass substrate: a)~5°; b) ~13°;c) ~30°; d) ~90°:
rapid growth of gypsum crystals and remaining mesoscopic clusters1.
References:
[1] N.Shahidzadeh, M.Schut, J.Desarnaud, M.Prat, D.Bonn, Scientific Reports 5, (2015),10335.
S05-P12
Crystal growth under high electric field: Analysis of the nucleation process
P. Hicher1*, R. Haumont1,2, R. Saint-Martin1, T. Baudin1, P. Berthet1
1
Equipe Synthèse, Propriétés et Modélisation des Matériaux, ICMMO, CNRS-UMR8182, Université Paris Sud, 15 rue
Georges Clémenceau, 91405 Orsay Cedex, France
2
Laboratoire Structures, Propriétés et Modélisation des Solides, CNRS-UMR8580, Ecole Centrale Paris, Grande Voie
des Vignes, 92295, Chatenay-Malabry Cedex, France
*e-mail: [email protected]
Single crystals of high quality and finely orientated are essential for the study of intrinsically
anisotropic physical properties. Indeed, properties of interest such as ferroic properties are
conditioned by the material’s structure, its chemical purity, crystallization quality and
crystallographic orientation. During crystal growth, the crystallization interface plays a key role in
the growth quality and orientation. Indeed, the crystallization front is the seat of mater diffusion and
energy transfer. Therefore, in order to grow high quality single crystals, control over the growth
interface is essential. Herein, we report first results on the effect of an applied external electric field
on the first stage of crystal growth, the nucleation. A device of strong external electric field has
been designed to fit in an optical mirror furnace. The interest of proceeding to crystal growth under
an applied electric field resides in the fact that such an external field is able to perturb the growth
interface and may, consequently, lead to a controlled crystallization front. Several works have
shown that it is indeed possible to use the electric field as a motion force of crystallization which
can, in some cases increase and, in other cases, decrease the nucleation rate regarding its effect on
the activation energy of nuclei [1,2,3]. The purpose of this work is to better apprehend the effect of
an external electric field on the nucleation stage of oxides materials growth with the aim to, at term,
be able to promote an orientation of growth of interest with the use of an external electric field as an
additional parameter to temperature and gas pressure. First results show that the applied external
electric field acts upon the first stages of crystal growth in terms of grains’ number, size and
orientation.
[1] W. Huang, S. Uda, S. Koh, Journal of Crystal Growth 307 (2007) 432-439
[2] R. Ghanasekaran, P. Ramasamy, Journal of Crystal Growth 79 (1986) 993-996
[3] D. Kashichiev, Journal of Crystal Growth 13/14 (1972) 128-130
SESSION 6
Mesocrystals and Nonclassical Crystallisation ⁄ Growth of Biological Materials and
Biologically-Controlled Growth
Multi Scale Approach of the Bio Crystal Status and Growth in Mollusc Shells
Alain Baronnet
CINaM-CNRS & Aix-Marseille Université, Campus Luminy, 13288-Marseille cedex, France
[email protected]
The way living organisms proceed to build up their partly crystalline shell or skeleton is still an enigma
for bio mineralogists, and there is yet no fully satisfying answer as to the crystal growth processes involved.
However consensus is reached that we deal here with non classical crystallisation. Beyond the fascinating
question, there is the challenge of finding a new way to nucleate and grow crystals.
To constrain the possible growth mechanisms involved in shells it was first a high need of thorough
characterization of the organo-mineral composite of the Ca-carbonate shell of some molluscs, the latter being
considered as model cases of biomineralization [1]. We present here mainly photon and electron microscopy
observations on marine and terrestrial gastropod and bivalve microstructures, made in presence of
recognized and acceptable artifacts.
The organo-mineral composite appears simultaneously at at least three levels of scale, with the smallest
at the nanometer scale. Organic matter component may show up as a pore-filling gel, sheets, fibers and
"nodes". The mostly crystalline component resembles the corresponding abiotic Ca-carbonate polymorphs
regarding their crystal-chemical, diffraction and optical properties. However quasi atomic structure imaging
by high-resolution transmission electron microscopy (HRTEM) shows locally considerable elastic
distorsions of the Ca2+- CO32- ionic columns, when in direct contact with fibrillar or sheet-like organic
matter. Numerous cationic and anionic vacancies are also diagnostic of such biogenic carbonates and bulk
dislocations are absent. Growth twinning may be present as in abiotic counterparts [2]. When averaged such
crystalline matter appears as partly disordered, i.e., may be seen as intermediate between the perfectly
crystalline state and the amorphous state. At the higher submicron scale, mostly crystalline, interconnected,
granules are ubiquitous building units of hardest parts of the shell [3]. They arrange as linear chains (thirdorder lamellae of the cross-lamellar microstructure), sheets (nacreous layer) or may form 3-D
microstructures (prismatic layer). Contiguous granules interpenetrate, strongly suggesting they were
emplaced as a soft, i.e. non crystalline, material. In case of aragonitic fibers (e.g., land snails), growth twin
planes propagate perfectly from granule-to-granule along the fibers which further supports that carbonate
crystallisation takes place after granule emplacement and that crystallisation propagates across their contact.
The growth mechanisms at work at the very border of the shell of farmed Crassostrea gigas are then
reported to illustrate the dynamics of shell growth. Here bio crystals of the prismatic layer nucleate each
already as a single crystal on a unique Ca-free organic nodule located on the periostracum. Crystalline but
xenomorph nuclei grow first by granule addition according to a 2-D process until they meet, thus squeezing
the organic wall between them. Then the tiling pattern is maintained and strengthened in each shell scale
while the secreting mantle is "pulling" prisms normal to it. The smooth growth front, irrespective of local
crystallographic orientations and microstructures, indicates a rate- and shape-controlling mantle acting very
close to the shell when mineralizing (interstitial growth). Occasional morphological instabilities of prisms in
spite of small growth rate support bulk diffusion-limited supply of Ca, and thus rather crystal growth from an
hydrogel [4] than crystal growth from a conventional aqueous solution.
At any stage of the shell development, the crystalline matter is found isolated from the surrounding by
organic matter and resulting isolated compartment growth mechanisms are found the same for land or marine
species. By the way, environmental signatures in a shell are not direct, as mitigated by the metabolism of the
shell-bearing organism. The shell development of molluscs appears thus largely bio-controlled at any scale
so that their species-specific shape be maintained.
References:
[1] Addadi L., Joester D, Nudelman F, Weiner S. Chem. Eur., 12 (2006) 980.
[2] Kobayashi I., Akai J. Jour. Geol. Soc. Japan, 100, 2, (1994) 177
[3] Baronnet A., Cuif J.P., Dauphin Y., Farre B., Nouet J. Min. Mag., 72, 2 (2008) 539
[4] Asenath-Smith E., Li H., Keen E.C., Seh Z.W., Estroff L.A. Adv. Funct. Mat., 22, 14 (2012) 2891
Bio-inspired Composite Crystals:
Incorporation of nanoparticles in calcite and zinc oxide single crystal
Alex Kulak1, Pengcheng Yang2, Mona Semsarilar2, Oscar Cespedes1,
Yi-Yeoun Kim1, Steven P. Armes2, Fiona C. Meldrum1*
1School
2Department
of Chemistry, University of Leeds, Leeds, UK
of Chemistry, University of Sheffield, Sheffield, UK
Composite materials based on inorganic host materials with well-defined structures and combined
functions with guest inorganic components had been centre of most pursued advanced materials due to their
extraordinary properties, which is origin from synergetic effects between the components. Many biominerals
created in nature, showed this unique feature, where significant amounts of macromolecules and small
molecules are intimately incorporated in single crystal domain, without disrupting the 3-D crystal lattice
structures. The exceptional hardness and toughness of biominerals account for this structural architecture.
In this work we present a facile one-pot method of the formation of novel heterostructures in which
inorganic nanoparticles are homogeneously distributed throughout an inorganic single crystal matrix. Our
strategy uses nanoparticles functionalised with diblock copolymers as a soluble crystal growth additive. We
show that gold and magnetic nanopaticles can be incorporated in the crystals (calcite and zinc oxide) in the
presence of suitable block-copolymers. The encapsulation of magnetite nanoparticles(MNP) and gold
nanoparticles (GNP) into a single crystals is investigated aiming at producing crystals with new functions and
properties. The encapsulation is achieved by precipitating calcium carbonate or zinc oxide in the presence of
nanoparticles with their surfaces modified by various chemicals. Two different MNP were used, one with
arylsulfonyl groups and another with alkylsulfonyl. It is shown that the level of incorporation in the host crystals
depends strongly on the nature of crystal and organic fragment attaches to MNP. A good degree of
encapsulation of MNP in the crystals is obtained. In the case of GNPs was used zwitterionic diblock
copolymer.
Fig. 1: TEM image of a thin section through MNPs in calcite; insert: a high resolution TEM image
showing the continuity of the crystal lattice around an embedded
magnetite particle.
Optimization of Crystallization using Dialysis Combined with Temperature
Control
Niels Junius1, Esko Oksanen2, Maxime Terrien3, Christophe Berzin1, Jean-Luc Ferrer1 and
Monika Budayova-Spano*1
1
Institut de Biologie Structurale UMR 5075 CEA-CNRS-UJF, 71 Avenue des Martyrs, Grenoble (France)
2
European Spallation Source, P.O. Box 176, Lund (Sweden)
3
Laboratory of Pulp and Paper Science and Graphic Arts, Grenoble INP-Pagora, Grenoble (France)
We have constructed a prototype of an integrated apparatus for the rational optimization of
crystal growth by mapping and manipulating temperature-precipitant concentration phase diagrams
[1].
Much instrumentation development in crystallization has concentrated on massive
parallelization of experiments and reduction of sample volume per experiment to find initial
crystallization conditions. Improving the size and diffraction quality of the crystals often requires
decoupling crystal nucleation and growth. This in turn requires controlling variables such as
precipitant and protein concentration, equilibration rate, temperature, that are all difficult
parameters to control in the existing setups. The success of the temperature controlled batch
method, of which the initial aim was to grow very large crystals for neutron crystallography [2,3],
convinced us that the rational optimization of the crystal growth has potential in structural biology.
Our approach differs from the current paradigm, since we propose serial instead of parallel
experiments, exploring multiple crystallization conditions with the same protein sample. The
sample is not consumed in the experiment and the conditions can be changed in a reversible
fashion. A major feature of our instrument is the software integration that allows visualization of the
crystals and in situ control of the temperature and composition of the crystallization solution.
Rational crystallization optimization strategies presented here allow tailoring of crystal size, and
diffraction quality, significantly reducing the time, effort and amount of expensive protein material
required for structure determination. The goal of the presentation is to demonstrate that a thorough
knowledge of the phase diagram is vital in any crystallization experiment. The relevance in
selection of the starting position and kinetic pathway undertaken to control most of the final
properties of the synthesized crystals is shown.
References:
[1] Budayova-Spano M., Patent FR10/57354, UJF (2010) (Extension: EP117730945, US13821053,
JP2013528746).
[2] Budayova-Spano M., Dauvergne F., Audifren M., Bactivelane T., Cusack S., Acta Crystallogr, D63
(2007) 339-347.
[3] Oksanen E., Blakeley M.P., Bonneté F., Dauvergne M.-T., Dauvergne F., Budayova-Spano M., J. R. Soc.
Interface, 6 (2009) S599-S610.
Influence of shear rate and surface area on nucleation kinetics in aqueous
solutions of glycine and urea reveals nonclassical nucleation mechanisms
Carol Forsyth, Danielle Trap, Jan Sefcik*
Department of Chemical and Process Engineering, University of Strathclyde, G1 1XJ, Glasgow, UK
[email protected]
Understanding crystal nucleation from solution is important for rationally designing and
controlling manufacturing processes that involve crystallization. Both batch and continuous
industrial crystallization processes typically involve fluid flow where supersaturated solutions
and/or suspensions of growing crystals are pumped or agitated. It is well known that fluid shear can
induce secondary nucleation and it has been also experimentally demonstrated that primary
nucleation can be affected by fluid shear as well [1,2]. In order to gain further experimental
evidence to facilitate improved understanding of effects of fluid shear on primary nucleation and
underlying nucleation mechanisms, we investigated nucleation in aqueous solutions of glycine and
urea under various flow conditions at a constant temperature.
Solutions were prepared by nanofiltration followed by slow cooling and they were then
subjected to either controlled fluid shear in Couette cells or agitation with magnetic stirring bars
under isothermal conditions. The onset of nucleation was always associated with a rapid increase in
turbidity, so induction times were readily obtained. The role of surface area was also studied by
changing the diameter of the inner cylinder of the Couette cell. Due to the stochastic nature of
nucleation, experiments were repeated numerous times and a statistical analysis was performed to
show that the number of repetitions was sufficient for accurate trends to be deduced.
In glycine solutions, the induction times of sheared solutions were considerably lower than
unsheared solutions, while a great care was taken to avoid seeding in solution or at solid-liquid
interfaces. This suggested that fluid shear had a profound influence on primary nucleation in these
solutions. In sheared solutions, a large number of small crystals formed in close succession, causing
solutions to rapidly go turbid, so it is proposed that shear enhanced the formation of a primary
nucleus which then initiated extensive secondary nucleation [3]. Increasing the average shear rate
was found to reduce the induction time in a power law relationship with an exponent of 0.98±0.1.
This indicated that the total strain applied was important for control of nucleation. Increasing the
surface area was found to notably decrease the induction times, which indicated that the surface also
played an important role. In situ dynamic light scattering measurements showed that colloidal scale
liquid-like clusters observed in mesostructured amino acid aqueous solutions [4] were increasing
their mean size upon continued shearing of solutions. This is consistent with these mesoscale
clusters (in the bulk liquid phase and/or at the solid-liquid interface) being involved in the primary
nucleation pathway in this system as proposed recently [1,5], where larger clusters correlated with
shorter nucleation induction times.
In urea solutions, study of induction times showed that nucleation appeared to be enhanced by
agitation and unstirred solutions had significantly longer induction times than stirred ones.
Surprisingly, a significant fraction of magnetically agitated vials (about 20%) appeared to nucleate
during the first few seconds of agitation, followed by the rest of vials over an extended period of
time. This trend was further investigated and it was found that longer aging of solutions at a
constant temperature resulted in a larger fraction of vials nucleating during the first few seconds of
agitation. Since urea is a very fast growing system (with crystal growth rate about 1 mm/s under
conditions studied), this was clearly not due to secondary nucleation, and it thus provides a strong
indication of a nonclassical nucleation mechanism in this system.
References:
[1] Jawor-Baczynska, A., Sefcik, J., Moore, B. D., Crystal Growth & Design, 13 (2013), 470.
[2] Liu, J., Rasmuson, A. C., Crystal Growth & Design, 13 (2013), 4385.
[3] Forsyth, C., Mulheran, P. A., Forsyth, C., Haw, M. D., Burns, I. S., Sefcik, J., Crystal Growth &Design, 15 (2015), 94.
[4] Jawor-Baczynska, A., Moore, B. D., Lee, H. S., McCormick, A. V., Sefcik, J., Faraday Discussions, 167 (2013), 425.
[5] Jawor-Baczynska, A., Moore, B. D., Sefcik, J., Faraday Discussions, (2015), doi: 10.1039/C4FD00262H.
Infrared light-induced protein crystallization
Kowacz Magdalena*1, Marchel Mateusz1, Juknaitė Lina2, Esperança José M. S. S.1, Romão Maria João.2,
Carvalho Ana Luísa.2, Rebelo Luís Paulo N.*1
1
Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Av. da República, 2780157 Oeiras, Portugal
2
UCIBIO - REQUIMTE, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de
Lisboa, 2829-516 Caparica, Portugal
*email: [email protected]; [email protected]
In this work we show that electromagnetic radiation in the infrared (IR) range can i) induce
protein nucleation from a metastable solution and ii) support proper ordering of biomacromolecules
into a crystal under conditions where, in the absence of radiation, only non-specific aggregation
takes place.
To uncover the underlying mechanism we have performed Fourier-transform Infrared
Spectroscopy studies revealing that the IR radiation can enhance mutual correlations of water
molecules in the protein hydration shell (makes protein interfacial water more structured). Our
results indicate that IR light induces changes comparable to those brought about by lowering the
temperature of water of hydration and thus encourages enhanced ordering of the water network.
Furthermore, the exposure of the protein solution to the IR radiation exerts an effect similar to
protein solubilisation (and native structure stabilization) by a buffer medium. The structured water
layer effectively “melts” upon addition of high concentration of inorganic salt.
The IR-induced mutual correlation of water molecules results in an ordered interfacial layer that
is polarized which can give origin to attractive interactions between like-charged
biomacromolecules and hence promote nucleation. Nevertheless, the structured character of the
hydration shell should help keeping individual protein molecules separated in solution (association
without coalescence) until the structure is destroyed e.g. by addition of salts. These features are of
great practical importance for protein crystallization. Inducing attraction of protein molecules at low
protein concentration should allow proteins to meet in space and find proper mutual orientation
(often referred as a rate limiting step in crystallization) before the crowding in solution (e.g. in the
course of vapour diffusion experiments) restricts geometrical rearrangements. Enveloping protein
within a protective layer of structured water, supporting protein native state, should further facilitate
steric adjustments before specific intermolecular contacts can form (following disruption of ordered
surface water e.g. on increasing precipitant concentration). Therefore, our results indicate that IR
radiation can be used to promote and kinetically control protein crystal formation. Examples are
shown for both model as well as “real-case” proteins that are difficult to crystallize.
Figure 1. IR and temperature induced changes in FTIR spectra of protein solution and corresponding crystallization
outcomes
Precursor-based bioinspired synthesis of magnetite nanocrystals
Mirabello Giulia1, Söğütoğlu Leyla-Can 1, Lendesr Jos J.M.1, Sommerdijk Nico A.J.M*1.
1
Eindhoven University of Technology, Building Helix
Het Kranenveld 14 P.O. Box 513
5600 MB, Eindhoven (Netherlands)
Magnetite (Fe3O4) is a widespread magnetic iron oxide, encountered in many biological and geological systems
[1]. It also has many technological applications, e.g. in magnetic data storage materials, inks, ferrofluids, scavengers in
water purification, but also in magnetic resonance imaging and controlled drug delivery [2-4]. Its magnetic properties
depend largely on the size and shape of the crystals, and at room temperature only 20-80 nm particles display singledomain ferrimagnetic behavior. In Nature, magnetotactic bacteria synthesize 30-140 nm magnetite crystals,
magnetically and crystallographically aligned in chains, thereby using their magnetic properties for navigation in the
Earth’s magnetic field [5]. While many biomineralization systems can be mimicked synthetically using additives and
templates [6], achieving control over the nucleation and growth of iron oxides is difficult, as they are only poorly
soluble in water, generally leading to polydisperse products. Nature’s strategy to overcome this issue is the use of
precursor phases for efficient transport of material and controlled conversion into crystalline products [7]. Indeed,
ferrihydrite (Feh) has been identified as a precursor in the magnetosomes of magnetotactic bacteria and the outer layer
of chiton teeth [8-9].
In our work presented here, we studied two synthetic routes to magnetite in water and at room temperature, one
starting from iron(II) through partial oxidation with potassium nitrate (KNO3) and one starting from iron(III) through
partial reduction with cysteine (Cys). In both cases, we make use of precursor phases (white rust or Fe(OH)2 for partial
oxidation, and ferrihydrite or Fe(OH)3 for partial reduction), from which the more stable magnetite is formed in a
second step. Further, we employ a computer-controlled titration setup to keep the reaction pH and reactant addition
rates under control. We thus aim at extending the control over aqueous magnetite formation by combining all these
strategies.
For the partial oxidation method, we show that is it possible to tune the crystal size of the final product by changing
the initial iron concentration, from 11 nm to 148 nm by going from 0.5 mM to 40 mM iron(II). This correlation
probably arises because the dimensions of the Fe(OH)2 precursor are affected similarly by the iron(II) concentration. In
the partial reduction route, the Cys was used as a sequestrant and reducing agent for iron(III), which is present in
solution or in the solid state as ferrihydrite. When the Cys is added to a solution of iron(III) and then the pH is increased
to alkaline conditions, the final product is magnetite. In contrast, when the Cys solution is added to a solution
containing Feh in the solid state, the Feh dissolves by forming a chelate complex with the Cys and then at alkaline pH
goethite (α-FeOOH) is obtained. The presented results show that magnetite can controllably be formed in water and at
room temperature, through various strategies, by combining precursor phases with controlled reactant titration.
Figure 1. TEM images of magnetite nanocrystals synthesized by partial oxidation at different iron
concentrations. a) 40 mM iron concentration, crystal size 148 ± 33 nm; b) 10 mM iron concentration, crystal
size 34 ± 9 nm; 0.9 mM iron concentration, crystal size 21 ± 5 nm. (scale bare 500 nm)
References:
[1] Author A., Author B., Author C., Journal, volume (year) page. (font: Times New Roman, size: 11, left aligned)
[1] R. M. Cornell, U. Schwertmann, The iron oxides: structure, properties, reaction , occurrences and uses. (WileyVCH Verlag GmbH & Co. KGaA, 2003).
[2] A.-H. Lu, E. L. Salabas, F. Schüth, Angewandte Chemie International Edition 46 (2007), 1222.
[3] S. Laurent et al., Chemical Reviews 108 (2008) 2064.
[4] C. T. Yavuz et al., Science 314 (2006) 964.
[5]F. R. B. a. B. D.A., Contributions to Microbiology 16 (2009) 182.
[6] A. Finnemore et al., Nat Commun 3(2012) 966.
[7] D. Faivre, T. U. Godec, Angewandte Chemie International Edition 54(2015) 4728.
[8] Baumgartner J. et al., Proc. Natl. Acad. Sci. U. S. A, 110 (2013), 14883.
[9] Gordon L. M. et al., Angewandte Chemie International Edition 53(2014) 11506.
Co-processing of Metformin Hydrochloride with Hydroxypropyl
Methylcellulose and Sodium Carboxymethlycellulose during Crystallization to
Manufacture Extended Release Tablets
Erdemir Deniz*, Chang Shih-Ying, Wong Benjamin , Rosenbaum Tamar, Kientzler Donald, Wang Steve, Desai
Divyakant, Kiang San
Drug Product Science and Technology, Bristol Myers Squibb, 1 Squibb Drive, New Brunswick NJ (USA)
Metformin with the dose range of 500 mg to 2550 mg is the first-line therapy for the
treatment of type 2 diabetes. The main challenge is to deliver the dose range using fewer easy to
swallow small size extended release tablets. In addition, the manufacturing process for extended
release tablets is challenging due to poor compactibility of metformin. To improve metformin
compactibility and reduce tablet size, a co-processing approach was explored. In this approach,
metformin was dissolved in water (solvent) and release controlling polymers, hydroxypropyl
methylcellulose (HPMC) and sodium carboxymethlycellulose (NaCMC), were suspended in
acetone/ethyl acetate mixture (anti-solvent). Mixing of solvent and anti-solvent formed metformin
crystals agglomerated with polymers. The agglomerates were filtered and dried using an agitated
dryer. They were lubricated with magnesium stearate and compressed into tablets. We demonstrated
that this process could accommodate higher drug load to achieve the target dissolution profile and
bioequivalence, leading to reduced tablet mass and size. The intimate mixing of HPMC and
NaCMC with metformin HCl through co-processing reduced the risk of segregation during
downstream handling and tableting. Moreover, with the improved metformin-polymer agglomerate
compactibility and flow, a direct compression method was feasible reducing the overall
manufacturing cycle time.
Heterogeneous nucleation and growth of calcium phosphate films on mica sheets
by vapour diffusion
Jaime Gómez Morales *, Cristóbal Verdugo Escamilla, Lourdes Vega Espinar, Jose Manuel Delgado López,
José Antonio Gavira Gallardo,
1
Laboratorio de Estudios Cristalográficos. IACT (CSIC-UGR), Avda. Las Palmeras, 4. 18100 Armilla (Spain)
Nucleation and growth of calcium phosphate on metallic substrates (mainly Ti and its alloys) is
a subject of intensive research because of the importance of coated implants for load bearing
applications in the orthopedic and dental fields. Few studies, however, have been carried out using
non-metallic substrates. Besides its interest at a fundamental level, these studies may have also a
biomedical relevance for the preparation of implants for non-load bearing applications, or as a
model for phosphorus recovery from waste water, or else for the preparation of biomimetic
functionalized surfaces with potential capability to induce the nucleation of protein crystals. In this
work we propose for the first time the vapor diffusion sitting drop method [1] to deposit bioinspired
calcium phosphate films on non-metallic substrates, i.e. mica muscovite. Later on the capability of
these films to induce the nucleation of proteins will be assessed using lysozyme as model protein.
Coated experiments have been carried out in a crystallization mushroom using 12 mica sheets
immersed in droplets composed of 50mM Ca(CH3COO)2 and 30mM (NH4)2HPO4 (Ca/P=5/3). A 3
mL aliquot of a 40mM NH4HCO3 solution was used as source of NH3 and CO2 gases. Experiments
lasted 1, 7, 14 and 21 days. Additionally, polyacrylic acid (PAA) was used as an additive.
Characterization was performed by optical microscopy OM, XRD, FT-IR and SEM.
Deposited calcium phosphate layers are composed of apatite nanocrystals (Ap) and octacalcium
phosphate (OCP), with increased amount of OCP at higher crystallization times. In the presence of
PAA deposited layers are composed of amorphous calcium phosphate (ACP). Preliminary results of
lysozyme crystallization indicate that coated mica sheets induce heterogeneous nucleation and
promote the growth along surface-liquid interface generating unexpected flat crystals.
Figure 1.Thin films composed of Ap nanocrystals and OCP produced by vapour diffusion method
References:
[1] J. Gómez-Morales, J.M. Delgado-López, M. Iafisco A. Hernández, M. Prat, Cryst Growth Des.11 (2011)
4802.
[2] G. Tosi, S. Fermani, G. Falini, J.A. Gavira, J. M. Garcia Ruiz, Cryst Growth Des.,11 (2011) 1542
POSTER
S06-P01
An Approach for Controlling Epitaxial Growth of Protein Crystal
by Using Microfluidic Device
Masatoshi Maeki*1,2, Ashtamurthy Pawate3, Masakazu Sugishima4, Keiichi Watanabe5,
Manabu Tokeshi1, Paul J. A. Kenis3, Masaya Miyazaki2
1
Hokkaido University, 13 Kita 8 Nishi, Kita-ku, Sapporo (Japan)
National Institute of Advanced Industrial Science and Technology (AIST), 807-1 Shuku, Tosu (Japan)
3
University of Illinois at Urbana-Champaign, 600 South Mathews Avenue, Urbana (U.S.A)
4
Kurume University School of Medicine, 67 Asahi-machi, Kurume (Japan)
5
Saga University, 1 Honjo, Saga, (Japan)
2
Three-dimensional analysis of protein provides essential information to the field of drug
discovery and elucidation of protein functions. However, generating high quality protein crystals is
considered as a bottleneck in the structure determination process. A microfluidic device for protein
crystallization has been reported as a useful tool to explore protein crystallization condition. We
have also reported the potential of the microdroplet for controlling single crystallization of protein.
In this study, we demonstrated an approach for controlling epitaxial growth of protein crystals by
using microfluidic device.
Two types of microfluidic devices were fabricated to confirm the effect of micro-space on the
protein crystallization. The depth of crystallization chambers was 10 µm and 50 µm. Lysozyme,
glucokinase from Pseudoalteromonas sp. AS-131 (PsGK), and heme oxygenase (HO) complex were
used as model proteins. Lysozyme and HO-complex were crystallized in an incubator at 20°C.
Protein crystallization experiment for PsGK was also performed in a cold room at 4°C.
At first, we carried out protein crystallization experiments by conventional method. Figure 1 (a)
shows the PsGK crystal prepared by conventional crystallization method and was aggregated
significantly. On the other hand, the microfluidic-based crystallization method can produce single
PsGK crystal in each crystallization chamber within the microfluidic device. However, the growth
behavior of protein crystal was dramatically changed by depth of the crystallization chamber, as
shown in Figure 1 (c) and (d). The rod-shaped PsGK crystal and plate-shaped PsGK crystal formed
in 50 μm and 10 µm crystallization chambers, respectively. We also found that the same crystal face
was preferentially grown by using 10 µm crystallization chamber. In case of lysozyme
crystallization, the lysozyme crystals were grown along to the (1 1 0) face. For these results, we
consider that the space limitation affects adsorption behavior of the protein molecules to the crystal
surface and induces epitaxial growth of protein crystal. Consequently, our microfluidic-based
approach provides a simple preparation method of the high quality protein crystals.
Figure 1. (a) PsGK crystal prepared by conventional method. (b) Microfluidic device used in this
study. There are 24 crystallization chambers. (c) PsGK crystal formed in the 50 µm crystallization
chamber. (d) PsGK crystal formed in the 10 µm crystallization chamber. Scale bar represents 200
µm.
S06-P02
Biogenic and non-biogenic struvite
Jolanta Prywer
Institute of Physics, Lodz University of Technology, ul. Wólczańska 219, 90-924 Łódź, (Poland)
The investigations of biogenic and non-biogenic struvite are performed in relation to infectious
urinary stone formation - struvite is the main component of this kind of stones. Biogenic struvite is
formed in artificial urine in the presence of microorganisms Proteus mirabilis (P. mirabilis). Nonbiogenic struvite is formed after addition of aqueous ammonia solution to the solution of artificial
urine. Such an addition emulates real infection similar to those caused by P. mirabilis.
Both biogenic and non-biogenic struvite crystals possess well developed crystallographic
surfaces. However, only biogenic struvite shows very characteristic surface structure [1]. The
structure of individual surfaces of biogenic struvite looks as if it was built from small crystallites.
On the basis of Scanning Electron Microscopy micrographs gaps between small units from which
the crystal is built may be identified, suggesting the porous nature of struvite. The size of the gaps is
in the range from tens to hundreds of nanometres. Taking in account this size it may be stated that
biogenic struvite is macroporous material. The internal structure revealed with the aid of Focused
Ion Beam microscope demonstrates that the porosity is characteristic not only for the crystal surface
but also for the volume of crystals [1]. The porosity is a unique feature of biogenic struvite.
Biogenic and non-biogenic struvite differs from each other also by crystal morphology while
the habit remains almost unchanged [2]. The differences in struvite morphologies of biogenic and
non-biogenic struvite are explained by electrostatic action between bacteria and crystal surfaces and
by the differences in relative growth rates of individual faces. In the presence of P. mirabilis
struvite crystals grow with relative growth rates in narrower range compared with those growing in
the absence of P. mirabilis [2]. Consequently, the growth in the presence of P. mirabilis gives
struvite crystals more regular compared with those in the absence of bacteria. It is suggested that P.
mirabilis cells mediate the struvite crystal formation by some physicochemical processes resulting
in the homogeneity in morphology.
Summarizing, biogenic struvite differs substantially from non-biogenic struvite. This means that
P. mirabilis are not only passive centres of nucleation, but actively mediate in growth processes.
Figure 1. Biogenic (a) and non-biogenic (b) struvite. Scale bar: 10 m.
References:
[1] Prywer J., Torzewska A., Płociński T., Urological Research, 40 (2012) 699–707.
[2] Sadowski R. R., Prywer J., Torzewska A., Cryst. Res. Technol. 49 (2014) 478–489.
The work was supported by the National Science Centre (Poland), Project No. 2013/11/B/ST3/03871.
S06-P03
Influence of tetrasodium pyrophosphate on struvite and carbonate apatite
formation
Marcin Olszynski*1, Jolanta Prywer1, Ewa Mielniczek-Brzóska2
1
Institute of Physics, Lodz University of Technology, ul. Wólczańska 219, 93-005 Łódź (Poland)
Institute of Chemistry, Environmental Protection and Biotechnology, Jan Długosz University of Częstochowa, ul. Armii
Krajowej 13/15, 42-200 Częstochowa (Poland)
2
Struvite and carbonate apatite (CA) are the main components of the so-called infectious urinary
stones. This kind of stones is formed when the urinary tract is colonized by bacteria producing
urease. The presence of urease in urine causes the series of chemical reactions resulting in increase
in pH and creation of supersaturation conditions for struvite and CA precipitation. Treatment of
infectious urinary stones is still a medical problem not fully solved. Modern treatment procedures
for infectious urinary stones do not bring completely positive clinical responses and, additionally,
the recurrence after treatment is on the level of 50% [1]. For these reasons, in recent years many
studies on the effect of different substances on the formations of struvite and CA have been
undertaken [2, 3]. The main aim of these studies is to find substances which potentially can improve
the effectiveness of treatment and decrease of recurrence level of infectious urinary stones.
In the present research we focus on the effect of tetrasodium pyrophosphate (abbreviated as
NaPP) on the nucleation and growth of struvite and CA in the environment of artificial urine. The
main goal of this research is to determine the effects of NaPP on the course and effectiveness of
precipitation processes occurring in the urine and evaluate the potential application of NaPP as a
inhibitor of infectious urinary stone formation.
Our spectrophotometric results supported by microscopic observations clearly show that the
increasing concentration of NaPP causes the delay of struvite nucleation and for a sufficiently high
concentration the crystallization processes are completely stopped. However, the presence of NaPP
leads to easier precipitation of amorphous phases e.g. CA. These results are explained based on the
chemical speciation analysis.
Figure 1. Struvite (arrow 1) and CA (arrow 2) formed in the solution of artificial urine in the absence (a) and presence of
NaPP (b). Scale bar:50 µm.
Acknowledgements
This work has been supported by the National Science Centre (Poland), Grant No. DEC2013/11/B/ST3/03871.
References:
[1] L. Benramdane, M. Bouatia, M.O.B. Idrissi, M. Draoui, Spectrosc. Lett. 41 (2008) 72–80.
[2] J. Prywer, M. Olszynski, J. Cryst. Growth, 375 (2013) 108-114.
[3] C.K. Chauchan, M.J. Joshi, Urol. Res. 36 (2008) 265-273.
S06-P04
Investigation of bacterial factors responsible for aggregation process of
carbonate apatite
Jolanta Prywer1, Rafal R. Sadowski*1, Agnieszka Torzewska2
1
Institute of Physics, Lodz University of Technology, ul. Wólczańska 219, 93-005 Łódź (Poland)
Department of Immunobiology of Bacteria, Institute of Microbiology, Biotechnology and Immunology, University of
Lodz, ul. Banacha 12/16, 90-237 Łódź (Poland)
2
The investigations are performed in relation to infectious urinary stone formation. This is
because that carbonate apatite, CA, is one of the main component of this kind of stones. Infectious
urinary stones are formed when urinary tract is infected by microorganisms producing urease,
mainly Proteus mirabilis (P. mirabilis). Even in the case of healthy person it may happen that some
phases may be formed within urinary tract due to high supersaturation of appropriate species in
urine. Usually, the formed phases are small enough (less than 2 µm) to excrete out the urinary tract,
without causing damage of the epithelial cells. Therefore, it seems that the nucleation and the
preliminary growth process are not the most important mechanisms leading to urinary stone
formation. Urinary stones cause problems when precipitating phases became large enough to retain
inside the urinary tract. Therefore, the aggregation is suspected to be one of the primary causes for
urinary stone formation. CA is present as an amorphous precipitate and does not form crystals of
defined morphology. It can easily aggregate with each other and with other components of the
infectious urinary stones.
The aggregation of particles precipitating from solutions is governed mainly by surfaces charges
characterized by zeta potential. In our previous work [1] zeta potential of CA, struvite (other
component of urinary stone) and bacteria have been measured and on this basis their aggregation in
artificial urine have been studied. On the basis of the results it is stated that from these three
components CA has the greatest ability to aggregate [1]. We have also observed an increased
aggregation process in the presence of bacteria. This results suggest that some bacterial factors are
responsible for increased aggregation of CA.
Therefore, the aim of the current studies is to analyze an influence of some bacterial factors on
the precipitation of CA and its aggregation. In particular, bacterial lipopolysaccharides (LPS) - the
major outer surface membrane components of P. mirabilis - are chosen to verify their ability to
increase the aggregation of CA. The sizes of CA aggregates formed without bacteria but for
different concentrations of LPS are compared with the sizes of CA formed in the presence of
bacteria. We also present particularly design experiment in which polystyrene latex beads, of
dimensions close to the dimensions of bacteria, are overcoated with LPS and in this way they mimic
the presence of bacteria in the solution of artificial urine. The results of our investigations give new
and interesting findings.
Acknowledgements
This work has been supported by the National Science Centre (Poland), Grant No. DEC2013/11/B/ST3/03871.
References:
[1] Prywer J., Sadowski R. R., Torzewska A., Crystal Growth & Design 15 (2015) 1446-1451.
S06-P06
Prenucleation clusters – quatarons – and crystal growth
Askhabov Askhab
Institute of Geology of Komi SC UB RAS, Syktyvkar (Russia), [email protected]
The situation with relatively stable existence of prenucleation clusters in crystal-forming media
after long enough discussions of last years has considerably changed [1]. It is already recognized
that formation of nuclei occurs through such clusters (the so-called two-step [2] or quataron [3]
mechanism of nucleation). However till now that fact that growth of crystals also occurs by means
of such clusters (the quataron model of growth of crystals) is practically ignored. This model acts as
alternative to two known concepts of crystals formation, confronting during all 20th century. We
mean the so-called Kossel concept usually named classical according to which crystals grow by
joining of separate atoms, ions, molecules, and Balarev concept of nonclassical growth in which the
basic building units are already formed crystalline particles (microblocks).
The essence of the quataron concept, we develop, consists in that at growth of crystals the basic
building units are special pre-crystallization clusters of "hidden" phase named quatarons [3]. At that
quatarons owing to specific character of their structure and properties form a special form of the
atomic-molecular organization of matter in the nanoworld. Quatarons, despite weak binding
energies (mainly, van der Waals bonds) keep their integrity, but represent dynamic structures. In
this they are similar to structureless molecules (clusters) of 4He3 [4]. In the process of increase in
the sizes (change of number and type of bonds between atoms) quatarons evolve from almost
structureless to more or less ordered objects. At establishing of chemical bonds between atoms,
quatarons form rigid structures (quatarons of carbon, for example, are transformed into fullerenes
[5]).
Easiness of change of distances between atoms and angles of bonds between them,
characteristic of quatarons, makes quatarons ideal building units. They practically without
resistance can join any faces of a crystal and reconstruct on them. Meanwhile the most probable
form of reorganization of quatarons on a growing face of a crystal is the formation of twodimensional nuclei.
It is specially noted that only quataron concept operates with nonequilibrium structural units at
description of crystals growth, the process, in turn, is possible only in nonequilibrium conditions,
this being one of the advantages of the quataron concept. At the same time, giving preference to the
quataron mechanism of crystals growth, we cannot exclude multi-route character of this process. In
the growth of crystals both separate atoms (ions), and molecular complexes, and substructural
cluster units, and three-dimensional nuclei, and crystal blocks can take part.
This work is supported by RFBR (14-05-00592а) and Grant of the President of the Russian
Federation for support of Leading Science School (SC-4795.2014.5).
References
[1] Gebauer A. et al. Chem. Soc. Rev., 3 (2014) 43 2348-2371.
[2] Vekilov P. Nanoscale, 2 (2010) 2346-2357.
[3] Askhabov A. Proc. of Russ. Miner. Society, 4 (2004) 133 108-123.
[4] Voigtsberger J. et al. Nature Comm. (2014) 5:5765 doi: 10.1038/ncomms.6765.
[5] Askhabov A. Physics of the Solid State, 47 (2005) 6 1186-1190.
SESSION 7
In-situ Monitoring ⁄ Control of Crystal Growth Processes ⁄ Crystal morphology
Mechanistic insights into the early stages of crystallization of rare-earth
carbonates
Rodriguez-Blanco, Juan Diego *1, Dideriksen, Knud1, Tobler, Dominique J.1, Sand, Karina K.2, Vallina,
Beatriz3, Benning, Liane G.3,4, Stipp, Susan1
1
Department of Chemistry, Nano-Science Center, University of Copenhagen, Copenhagen (Denmark)
2
Lawrence Berkeley National Laboratories, Berkeley, California (USA)
3
School of Earth and Environment, University of Leeds, Leeds (United Kingdom)
4
Research Center for Geosciences, GFZ, Interface Geochemistry Section, Potsdam, Germany
Rare-earth element (REE) carbonates are important compounds that are usually found in
carbonatite deposits (e.g., Bayan Obo, China; Mountain Pass, USA). Their consumption is
considered an economic indicator because there is currently a strong demand for several REE (e.g.,
La, Nd, Eu, Dy) and this demand is expected to increase even more in the next decades. Two of the
most important minerals in carbonatite deposits are lanthanites (REE2(CO3)3·8H2O) and
bastnaesites (REE(OH,F)CO3), which include La, Ce, Pr, and Nd as major elements but also often
traces of heavier rare-earth elements (e.g., Sm, Eu, Dy). Most research to date has focused on the
structural determination and crystal chemistry of natural samples. However, there is little
information about the crystallisation mechanisms of these minerals, the mobility and fate of the
REE during their formation and the factors governing mineral stability. Do REE-carbonates
crystallise in the same way as other divalent metal carbonates (e.g., Ca2+, Mg2+ [1]), through the
breakdown of a nanoparticulate amorphous precursor? Or do they form through oriented attachment
of nanocrystalline particles as for other salt systems (e.g., CaSO4 [2])?
To answer these questions, we applied UV-Vis spectrophotometry combined with synchrotronbased pair distribution function (PDF) analysis, Fourier transform infrared spectroscopy (FTIR),
thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC) and powder X-ray
diffraction (XRD), to quantify changes in the REE3+-bearing carbonate local structure, composition,
stability and crystallization pathways. Our results revealed that all REE3+ carbonates form from
amorphous precursors at ambient temperature and the ionic potential of the REE3+ cation controls
the hydration, precursor lifetime and the crystallisation kinetics of the REE3+ carbonates.
Furthermore, PDF results confirmed short range ordering (<15 Å) and showed that the local
structure differed depending on the REE3+ cation. Our new data identify the parameters that
kinetically control the crystallisation of REE-bearing carbonates from solution, providing critical
information to help with prospecting approaches to locate new REE deposits, reprocessing ores or
recycling materials that contain REE to enhance recovery.
References:
[1] Rodriguez-Blanco J.D., Shaw S., Benning L.G. Nanoscale, 3 (2011) 265-271.
[2] Van Driessche A.E.S., Benning L.G., Rodriguez-Blanco J.D., Ossorio M., Bots P., García-Ruiz J.M.
(2012) Science, 336 (2012) 69-72.
From Amino Acids to Cements: Crystallization Studied by CLASSIC NMR
Hughes, Colan E.1*; Williams, P. Andrew1; Keast, Victoria L.1; Edwards-Gau, Gregory R.1;
Charalampopoulos, Vasileios G.1; Harris, Kenneth D. M.1;
Gardner, Laura J.2; Walling, Sam A.2; Bernal, Susan A.2; Provis, John L.2
1
2
School of Chemistry, Cardiff University, Park Place, Cardiff, CF10 3AT (U.K.)
Department of Materials Science and Engineering, University of Sheffield, Mappin Street, Sheffield, S1 3JD (U.K.)
The CLASSIC (Combined Liquid- And Solid-State In-situ Crystallization) NMR technique [1]
has been developed recently to monitor the evolution of both solid and liquid phases as a function
of time during crystallization. By using NMR methods that selectively detect different motional
regimes, the technique achieves essentially simultaneous monitoring of NMR spectra of both the
crystallization solution and the crystalline products (including transformations of the solid phase).
Variants of this strategy have been applied to study a range of crystallization systems, including
amino acids (both proteinogenic and aminobenzoic acids), phosphine oxides, co-crystal systems
(both stoichiometric and solid solutions) and cements. These studies have led to new insights on
polymorphic evolution, discovery of hitherto unknown intermediates in crystallization pathways,
understanding of the pre-nucleation state of solutions and knowledge of crystallization kinetics [2].
The versatility of the technique will be illustrated by studies of the competitive growth kinetics
of polymorphs of glycine (Figure 1a) and the formation of distinct aluminium sites during the
setting of a hydraulic cement (Figure 1b). The results for glycine demonstrate that the presence of a
small, undissolved amount of the thermodynamically stable but slow-growing γ polymorph has a
complex effect on crystallization from water. Whilst the formation of the α polymorph is observed
as anticipated, the growth kinetics are affected significantly by the presence of the γ polymorph. For
the calcium aluminate cement, the observation that different types of aluminium coordination site
are present at different stages of the hydration reaction allows known physical changes in the
formation of this type of cement to be understood on the basis of the chemical changes occurring.
13
Figure 1. (a) C NMR peak intensities for the  (red) and  (green) polymorphs of glycine during crystallization from
27
H2O by slow cooling. (b) Solid-state Al NMR spectra recorded as a function of time during the
hydration reaction of calcium aluminate cement. Spectral evolution over 12 hours is shown.
References:
[1] Hughes, C. E., Williams, P. A., Harris, K. D. M. Angew. Chemie Int. Ed., 2014, 53, 8939-8943.
[2] Hughes, C. E., Williams, P. A., Keast, V. L., Charalampopoulos, V. G., Edwards-Gau, G. R.,
Harris, K. D. M. Faraday Discuss., 2015, in press [DOI: 10.1039/C4FD00215F]
An Investigation into the Particle Growth Pathway of Precipitated Fenofibrate
Tierney, Teresa B.1, Rasmuson, Åke C.1,2, Hudson, Sarah P.*1
1
Synthesis and Solid State Pharmaceutical Centre, Materials and Surface Science Institute, Chemical and
Environmental Science, University of Limerick, Limerick, Ireland.
2
Department of Chemical Engineering and Technology, KTH Royal Institute of Technology, Stockholm, Sweden
Nano to small-micron sized particles of the hydrophobic drug, fenofibrate, were prepared by
controlled crystallisation in order to influence its dissolution behaviour. An antisolvent precipitation
process successfully generated nanoparticles (200-300 nm) which matched the size and dissolution
behaviour of a commercial wet-milled nanoformulation of the drug, but by a more energy/time/cost
efficient approach. Although the nanoparticle formation process was straightforward, retaining the
size of the freshly precipitated nanoparticles in suspension and during isolation was challenging.
Additives were employed to temporarily stabilise the nanosuspension, and extend the time window
for nanoparticle isolation. Precipitated particles were isolated by immediate freeze-drying, but
stresses which occur during the drying process, were found to destabilise the fragile nanoparticle
system. Freeze-drying did however induce an interesting growth pathway, whereby nanoparticlebased aggregates gradually evolved into uniform and highly-defined parallelepiped structures of
~4µm. While oven-drying produced similar structures, a visually different growth pattern was
observed, due to faster kinetics at elevated oven-drying temperatures. Time-resolved morphological
analysis of the freeze-dried particles initially induced speculation of a non-classical ‘mesocrystal’
growth pathway. However, an investigation of the electron diffraction patterns and cross-sectional
inner surfaces of particles contradicted this initial hypothesis.
Figure 1. Two proposed particle growth pathways for precipitated, freeze-dried fenofibrate
Growth of nanostructured carbon materials by Supersonic Molecular Beams of
C60 on Cu studied by Surface Electron Spectroscopies
Aversa Lucrezia*1, Tatti Roberta1, Taioli Simone2,Garberoglio Giovanni2, Speranza Giorgio3, Cavaliere
Emanuele4, Gavioli Luca4, Iannotta Salvatore5, Verucchi Roberto1
1
IMEM-CNR Trento, Via alla Cascata 56/C, Povo (TN) (Italy)
2
ECT* and TIFPA, Via Sommarive 18, Povo(TN) (Italy)
3
CMM-FBK, Via Sommarive 18, Povo (TN) (Italy)
4
Università Cattolica del Sacro Cuore, Via Musei 41, Brescia (Italy)
5
IMEM-CNR, Parco Area Delle Scienze 37/A, Parma (Italy)
Fullerene (C60) is a molecule fully formed of carbon that can be used, owing to its electronic and
mechanical properties, as precursor for the growth of carbon-based materials. The interaction of C60
particles, using Supersonic Molecular Beams that are characterized by a tunable translational
kinetic energy, with metal surfaces can produce different processes starting from chemisorption up
to cage opening or breaking, either thermally or kinetically, opening the way to the formation of
nanostructured carbon materials. Having in mind the primary target, i.e. the strong interaction with
the surface and formation of new carbon materials, we achieved the synthesis of graphene, single
layer thin film on Cu(111) surface kept at 645°C by using C60 precursor and the Supersonic
Molecular Beam Epitaxy (SuMBE) approach. This result has never been observed in the same
experimental conditions in molecular beam epitaxy experiments (MBE) and has been investigated
by experimental and theoretical studies, paving the way for graphene synthesis on other metal
substrates even at lower processing temperatures. In this work we present the investigation of C60
impacts on copper at different kinetic energies with the aim of breaking it and forming carbonbased materials. Using a variety of electron spectroscopy (XPS, UPS, AES) and microscopy
techniques (STM), Raman characterization and first-principles simulations, we discuss the
chemical-physical mechanisms on which thermally-assisted graphene growth by SuMBE is
achieved.
Grain growth competition in directionally solidified multi-crystalline silicon
studied with in situ X-ray imaging techniques
Thècle Riberi-Béridot*1, Nathalie Mangelinck-Noël1, Amina Tandjaoui2, Guillaume Reinhart1, Maria
Tsoutsouva1, Gabrielle Regula1, José Baruchel3
1
Aix-Marseille Université, CNRS, IM2NP UMR CNRS 7334, Campus Saint Jérôme, case 142, 13397 Marseille Cedex
20 (France)
2
Laboratoire de Mécanique de Lille (UMR CNRS 8107), Ecole Centrale de Lille, CS-20048, F-59651 Villeneuve d’Ascq
Cedex (France)
3
ESRF, 71, avenue des Martyrs, CS40220, 38043 Grenoble Cedex 9 (France)
Crystalline silicon (Si)-based photovoltaic cell technology is well-established and currently
represents about 90% of the world PV market. Grain structure, impurities and defects induced
during the crystal growth process, have a major impact on the final PV efficiency. However, the
involved fundamental mechanisms that define the final grain structure are still not fully understood
preventing an efficient and reproducible control of the silicon crystallization.
Experiments based on the Bridgman solidification technique with X-ray imaging are performed.
The unique experimental device developed allows following in-situ and in real time the formation
of the grain structure. During the solidification, two imaging characterisation techniques using Xray synchrotron radiation at ESRF (Grenoble, France) are combined: X-ray radiography and X-ray
Bragg diffraction topography. The X-ray radiography method brings information on the
morphology and kinetics of the solid/liquid (S/L) interface. The X-ray Bragg diffraction topography
gives additional information about the evolution of the grain shape and structure, the defect
formation and the local level of crystal distortion during growth (Figure 1). Additionally, Electron
Backscattered Diffraction (EBSD) has been used to reveal the crystalline orientations of the grains
and the twin relationships.
500 µm
Solid-liquid
interface
(a)
(b)
(c)
(d)
Figure 1. X-ray imaging topography during the solidification (cooling rate: R = 0.2 K/min at t0 to R
= 4 K/min at t0 + 1200 s, temperature gradient: G = 20 K/cm) of a Si (6N) sample. Zoom on a
diffraction spot at (a) t0 + 180 s; (b) t0 + 420 s; (c) t0 + 900 s; (d) t0 + 1246 s.
New grains formed during growth have two main origins: random nucleation and twinning. It is
demonstrated that the solidified samples are dominated by ∑3 twin boundaries formed by twinning
on {111} facets. Moreover, thanks to the in situ characterization of the growth, it is shown that
twins nucleate on {111} facets located at the sides of the sample (Figure 1) and at grain boundary
grooves. The occurrence of multiple ∑3 twins during growth prevents the initial grains from
developing all along the sample, and twin boundaries with higher order coincidence site lattices can
form at the encounter of two grains in twin position. The grain competition phenomenon following
nucleation and twinning acts as a grain selection mechanism leading to the final grain structure.
Evaporation Crystallization of Glycine
J. Puranen, M. Louhi-Kultanen
Laboratory of Separation Technology, School of Engineering Science,
Lappeenranta University of Technology; P.O. Box 20, FIN-53851 Lappeenranta Finland
[email protected]
For many decades, understanding and controlling of solution crystallization and
crystal polymorphism have been areas of intensive research. In order to ensure that the
correct polymorph is produced, the ability to monitor and control the crystallization process
and polymorph transformation is critical. Amino acids are widely used as model
compounds because of their well-known physical properties and their ability to crystallize
in a range of polymorphs. The simplest amino acid is glycine (NH2CH2COOH), which is
found in various proteins and enzymes. Glycine crystallizes in three polymorphic forms at
atmospheric pressure: α, β and γ, from which the β form is a metastable form.
The present study focuses on the evaporation crystallization of glycine from
aqueous solutions and water-ethanol mixtures with different ratios at controlled conditions
(i.e. aerodynamic conditions, temperature, air humidity and mass transfer between the gas
and liquid) with an evaporation chamber equipment developed especially for polymorph
screening. This approach provides more precise analysis results for polymorph screening
and evaporation rates, as well as enhancing control of solvent evaporation at the desired
temperature.
Evaporation crystallization experiments were carried out with the evaporation
chamber equipment at 40 °C, 50 °C and 60 °C with constant flow velocities of 0.2 and 0.3
m/s at ambient pressure and temperature.
In this study, the obtained polymorphs of glycine crystals (analyzed with X-Ray
powder diffraction and optical microscopy) and the empirical evaporation rates are
assessed and evaluated. The influence of the evaporation rate of the solvent and solvent
mixtures on the crystal formation and crystal structure of the glycine is also discussed.
Polymer versus monomer action on the growth and habit modification of sodium
chloride crystals
E. Townsend1, W.J.P. van Enckevort1, J.A.M. Meijer2, E.Vlieg1
1
Radboud University Nijmegen, The Netherlands; 2Akzo Nobel B.V., Deventer, The Netherlands
In this investigation, we have looked into the use of polymers and monomers as habit modifiers
and anticaking agents for sodium chloride.
We show that amide functional groups cause {111} faces to propagate on sodium chloride
crystals and that polymer amides give a 1-2 orders of magnitude greater effect than the
corresponding monomers on the habit modification of sodium chloride.
We have also shown that the alcohol functional group does not have an effect on the surface or
habit modification but that, when in a polymer form, leads to macrostep formation and acts as a
nucleation inhibitor. The latter also holds true for other polymers that we have also tested.
Finally, we found that no amino acids, apart from glycine, have an effect on the morphology of
NaCl crystals.
Application of LPE method for producing of high-performance scintillating screens
based on the single crystalline films of multicomponent garnets
Yu. Zorenko1,2*, T. Zorenko1,2, V. Gorbenko1,2, T. Voznyak2, O. Sidletskiy3, Ya. Gerasymov3, A. Fedorov5
1
Institute of Physics, Kazimierz Wielki University in Bydgoszcz, 2 Powstańców Wielkopolskich str., 85090 Bydgoszcz (Poland)
2
Electronics Department, Ivan Franko National University of Lviv, 5 Dragomanova str.,79017 Lviv, Ukraine
3
Institute for Single Crystal NAS of Ukraine, 60 Lenin av., 61178 Kharkiv (Ukraine)
Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw (Poland)
4
The liquid phase epitaxy (LPE) play a key role at the obtaining the high–density single crystalline
film (SCF) scintillators based on different oxide compounds [1, 2]. Most hot topic today is the
creation of SCF scintillation screens in 2D/3D detectors used for micro-imaging applications under
excitation by X-rays or synchrotron radiation [2]. This report presents our achievements in the
development of new types of SCF scintillators based on the A3-xAl5-yGayO12:Ce garnet compounds;
A=Gd, Lu, Tb and their combination at x=0÷3.0 and y=1.5÷3.5, using the LPE method from PbO and
BaO based fluxes onto Y3Al5O12 and Gd3Al2.5Ga2.5O12 (GAGG) substrates. The bulk crystals of
multicomponent garnets are now on the top list of most efficient oxide scintillators with the light yield
(LY) up to 60000 Ph/MeV [3]. Therefore, creation of SCF analogues of such garnets is now very actual
task in frame of producing scintillation screens for X-ray imaging with submicron spatial resolution [2].
We report in this work optimised content and excellent scintillation properties of SCF scintillators
based on the Gd3-xLuxAl5-yGayO12:Ce, Gd3Al5-yGayO12:Ce and Tb3-xGdxAl5-yGayO12:Ce multicomponent
garnets grown by LPE method. Namely, the Gd1.5Lu1.5Al2.75Ga2.25O12:Ce and Gd3Al2.5Ga2.5 O12:Ce SCF,
grown from BaO based flux, shows comparable LY with high-quality Cz grown bulk crystals analogues
but faster scintillation decay response. These SCF possesses the highest LY values from all obtained in
our group garnet SCF scintillators exceeding by at least 1.6-1.7 times the LY of best samples LuAG:Ce
SCF analogues, grown from PbO based flux. At the same time, the quality of these SCF scintillators is
strongly influenced by the high-viscosity of BaO based melt.
The LY of SCF of Gd1.5Lu1.5Al3-2.75Ga2-2.25O12:Ce and Gd3Al3-2.75Ga2-2.25O12:Ce garnets, grown from
PbO based flux, is notable lower (by at least 2.5 and 6.5 times, respectively) than LY of their analogues
grown from BaO flux due to strong quenching influence of Pb2+ flux related impurity. Meanwhile, these
SCF also possesses very fast scintillation response.
With the aim of enhancing the energy transfer from the garnet host to the Ce3+ ions, the SCF of the
Tb3Al5-yGayO12:Ce and Tb3-xGdxAl5-yGayO12:Ce garnets were crystallized by the LPE method onto
GAGG substrates and the luminescent and scintillation properties of these SCFs were studied as well.
Due to the efficient Tb3+Ce3+ and Gd3+Tb3+ Ce3+ energy transfer in the mentioned garnet
matrices, we have observed strong increasing the LY of SCFs of these compositions. Namely, the LY of
Tb3Al3Ga2O12:Ce and Tb1,5Gd1,5Al3 Ga2O12:Ce SCF, grown from PbO-based flux are equal to 1.2 and
1.5 with respect to LuAG:Ce SCF and comparable with the LY of Gd3Al2Ga3O12:Ce and Gd3Ga2.5
Al5O12:Ce bulk crystals. To our knowledge, these are the highest LY values obtained in SCF
scintillators so far, prepared from PbO based flux [4]. The role of Ga3+ co-doping in the improvement of
the efficiency energy transfer in Tb3-xGdxAl5-yGayO12:Ce matrixes was discussed. The comparison
between the luminescent and scintillation properties of A3-xAl5-yGayO12:Ce SCF; A=Gd, Lu, Tb, grown
from PbO and BaO fluxes was performed as well.
References:
[1] Yu. Zorenko, V. Gorbenko, T. Martin, P.-A. Douissard, , et all, Radiation Measurements 56 (2013) 415.
[2] Т. Мartin, A. Koch, Journal of Synchrotron Radiation, 13 (2006) 180.
[3] K. Kamada, T. Endo, K. Tsutumi, J. Pejchal, M. Nikl, et all., Cryst. Growth Des., 11 (2011) 4484.
[4] P.-A. Douissard, T. Martin, F. Riva, Y. Zorenko, e. all, Proc. SCINT2015 conference, San-Francisco, 2015.
This work was realized within the Polish NCN No 2012/07/B/ST5/02376 and Ukrainian SL-20F projects.
POSTER
S07-P02
New crystallizer design for scaling salts crystal growth research avoiding crystal
attrition
Torres-Serrano, Víctor Manuel*1,2, Wagterveld, Martijn1, Miedema,Henk1, Witkamp, Geert-Jan1,2
1
Wetsus, European Centre of Excellence for Sustainable Water Technology, P. O. Box 1113 8900 CC, Leeuwarden
(The Netherlands)
2
Department of Biotechnology, Delft University of Technology, Julianalaan 672628 BC, Delft (The Netherlands)
A special glass-made reactor design is used for the study of crystallization of calcium carbonate
and other scaling salts offline and on-line. Changes in the (hydrodynamic) regime in the reactor,
and the presence of foreign (organic and inorganic) substances, including fresh and recycled
antiscalants on scaling salts crystal growth are investigated.
The cylindrical crystallizer has a draft tube inside and it is special bottomed-shaped. This
configuration helps to keep the solution in motion (in circles) very gently inside the reactor
avoiding crystal attrition. Different positions and diameter/length ratios are tested to find the
optimal hydrodynamic regime for crystal growth. Seeded Constant composition and non-seeded
free-drift experiments are conducted under controlled experimental conditions. In the first case, and
for calcium carbonate for instance, a metastable supersaturated solution containing Ca2+ and
CaCO32- and calcite seeds crystals is kept in motion by means of either mechanical agitation
(impeller) or pneumatically. Pneumatic agitation is reached by pumping a N2 and CO2 gas mixture
from the bottom of the reactor. Supersaturation is kept constant by maintaining pH constant
(between 7.8 and 7.9) injecting the reactants (in this case NaHCO3 and CaCl2) gradually and
separately, avoiding supersaturation to occur until the moment of mixing. The feeding CO2 partial
pressure is also known at any moment and it is changed according to the pH value as well. The
temperature is also controlled and fixed at 298 K by circulating cooling water through the reactor’s
outer jacket. The partial pressures of gases in the head space are controlled by adding a CO2/N2
mixture, ensuring there is no CO2 exchange between the solution and the space on top of the
reactor. Calcium carbonate crystal growth is then followed avoiding the effect of attrition, off line
but also on-line. A closed loop including a flow cell is performed to follow the growth of the
crystals by light scattering [1], Atomic force microscopy (AFM) [2,3] high speed imaging [4],
infrared spectroscopy or Raman spectroscopy [5].
A new special reactor design offers (hydrodynamic) flexibility and the possibility of avoiding
crystal attrition on the study of calcium carbonate crystal growth. By having the possibility of
following the crystallization process online and avoiding attrition, it is possible to investigate more
in detail the effects of the presence of foreign ions/impurities, and the effectiveness of fresh and
recycled antiscalants.
References:
[1] Ralph. Jonasson, Kevin Rispler, Brian Wiwchar, William D. Gunter, Chemical Geology, 132 (1996) 215225.
[2] Alexander E. S. van Driessche, Mike Sleutel, Crystal Research and Technology, 1-23 (2013)
[3] Manijeh M. Reyhani, Allan Oliveira, Gordon M. Parkinson, Franca Jones, Andrew L. Rohl, Mark I.
Ogden, International Journal of Modern Physics B, 16 (2002) 25-33
[4] Sigurd Bauerecker, Peter Ulbig, Victoria Buch, Luboš Vrbka, Pavel Jungwirth, Journal of Physical
Chemistry C, 112 (2008) 7631-7636.
[5] Jeroen Cornel, Marco Mazzoti, Industrial & Engineering Chemistry Research, 48 (2009) 10740-10745.
S07-P03
Development of in-situ observation svorontystem for high-temperature
liquid/solid interfaces: application to solid-source solution growth of AlN
Yoshihiro Kangawa*1, Hideto Miyake2, Michał Boćkowski3, Koichi Kakimoto1
1
2
RIAM, Kyushu University, Fukuoka 816-8580 (Japan)
Graduate School of Regional Innovation Studies, Mie University, Mie 514-8507 (Japan)
3
Institute of High Pressure Physics, PAS, Unipress, 01-142 Warsaw (Poland)
Aluminum nitride (AlN) and related compound semiconductors, such as AlGaN, have attracted
much attention for use as active layers in deep-UV light-emitting diodes. In order to design AlGaN
devices with low dislocation densities, it is indispensable to develop a high quality AlN substrate. In
2011, we have developed an AlN solid-source solution growth (3SG) method which used Li3N as a
nitrogen source instead of N2 gas. [1] It was found that growth mode of the material influences on
the dislocation propagation and annihilation phenomena. [2] In
the present work, we developed an in-situ observation system for
high-temperature liquid/solid interfaces, and applied it for 3SG of
AlN to understand the initial growth mode.
Figure 1 shows a schematic of the experimental apparatus
used for in-situ observations of the morphologies of liquid/solid
interfaces at high temperatures. We have observed the liquid/solid
interfaces through transparent solid materials, i.e., quartz window
and AlN/α-Al2O3 substrate. Here, the molar ratio of the source
materials was Al:Li3N = 4:1. At high temperatures, Al and Li3N
powders melt and form Li-Al-N solution. Figure 2 shows optical
images of the Li-Al-N solution/substrate interface. At 23min after
the temperature increase (1350°C), we observed the macrostepFigure 1. Schematic of inflow growth mode as seen in Fig. 2. Although the grown crystal
situ observation system.
was polycrystal under the present growth
condition, the result suggests that this
system could be a powerful tool for
investigating inter-facial phenomena at
high-temperature liquid/solid interfaces
and optimizing crystal growth conditions.
Acknowledgements:
One of the authors (YK) thank the partial
support by a FY2014 Research Exchange
Program between Japan Society for the Promotion of Science (JSPS) and Polish Academy of Science (PAS),
and KAKENHI Grant Number 25420712.
References:
[1] Y. Kangawa, R. Toki, T. Yayama, B. M. Epelbaum, K. Kakimoto, Appl. Phys. Express, 4 (2011) 095501.
[2] Y. Kangawa, H. Suetsugu, M. Knetzger, E. Meissner, K. Hazu, S. F. Chichibu, T. Kajiwara, S. Tanaka, Y.
Iwasaki, K. Kakimoto, Jpn. J. Appl. Phys. (Submitted).
S07-P06
Peculiarities of sapphire nitridation under the influence of
the high-energy electron beam
Milakhin Denis*1, Malin Timur1, Mansurov Vladimir1, Galitsin Yuri1, Zhuravlev Konstantin1,
Bakarov Askhat
1
Rzhanov Institute of Semiconductor Physics of the Siberian Branch of the Russian Academy of Science,
630090, Novosibirsk, Russia
Nitridation of the sapphire is the most important step in the growth of the III-nitrides on the
sapphire. This process involves exposing a substrate to a flow of ammonia at an elevated
temperature. Nitridation of the reconstructed surface of the sapphire enriched by aluminum atoms is
of special interest, since the presence of metallic bonds on the surface improves the quality of the
structure.
The nitridation process during ammonia MBE has been studied using reflection highenergy electron diffraction as the reflex of the AlN crystalline phase appears near the reflex of the
sapphire. The experimental results were processed in a special program, which measured the
intensity of the most informative reflexes. Then, we plotted the dependence of the intensity of
appeared reflexes of the AlN crystalline phase on time in the form of kinetic curves. During the
processing of the experimental results of nitridation on the reconstructed surface of sapphire it has
been found that high-energy electrons have an impact on the process.
By heating of the samples by heat radiation from the heater, reconstruction of the surface (1x1)
appears. Then the sample is heated to the temperature of 1150 C and the surface of the sapphire
(1x1) starts to change to ( 31  31 ) R9° reconstruction. It is characterized by the sapphire surface
depletion of oxygen and aluminum enrichment. However, in our previous work it is shown that
there is only a partial recovery of aluminum to the metal state [1].
We have found out that the surface reconstruction of sapphire (1x1) is nitridized for 10 minutes
in a 25 sccm ammonia flow, whereas the surface with the reconstruction of ( 31  31 ) R9° is not
nitridized and the AlN crystalline phase is not formed. It has been noted that under the influence of
fast electrons with the energy of 11 keV, the irradiated section of the ( 31  31 ) R9°
reconstructed surface is destroyed within 10 minutes, the surface of the sapphire is restored to its
original state with the reconstruction (1x1), and then it is successfully nitridized.
To investigate the effect of a high-energy electron beam on the nitridation process, experiments
were conducted to destroy the ( 31  31 ) R9° reconstruction to (1x1) at different temperatures
(750 °C, 825 °C, 900 °C). The duration of the impact and the intensity of the electron beam varied.
The influence of the pulse width depending on the pulse ratio to the kinetics of nitridation of
sapphire was studied: in the first case, the momentum of an electron beam was continuous; in the
second case the relative pulse duration was S = 2, and in the third one it was S = 20. So we could
restore the nitridation kinetics in the absence of exposure to electrons. It has been shown that
eliminating the influence of the electron beam the process of forming the AlN crystalline phase
goes on appreciably slower and is different from the process in a continuous exposure in
k = 6 times. In case of low intensity the nitridation process also slows down. Using the obtained
kinetic curves of the nitridation process has made it possible to investigate the influence of the
degree of completion of the process of nitridation on the further growth of the AlN buffer layer.
This work is supported by RFBR (grant № 13-02-00985).
References:
[1] D.S. Milakhin, T.V. Malin, V.G. Mansurov, J.G. Galitsin and K.S. Zhuravlev, Semiconductors,
Volume 49, 2015, 925-931.
S07-P07
Using modifiers to mitigate salt crystallization damage in porous building materials: an optical microscopy study of borax and sodium sulfate Granneman Sanne*1, Lubelli Barbara1,2, van Hees Rob1,2,Shahidzadeh Noushine3
1
Technical University of Delft, Julianalaan 134, Delft (The Netherlands), [email protected]
2
TNO Technical Sciences, Van Mourik Broekmanweg 6, Delft (The Netherlands)
3
University of Amsterdam, Institute of Physics, WZI, Science Park 904, Amsterdam (The Netherlands)
*email: referring author email
Crystallization of soluble salts in porous building materials is a ubiquitous problem, and a threat to the preservation of our monumental buildings. Lime‐based mortars, commonly used in historic masonry, are especially prone to salt damage due to their low mechanical strength. The deterioration such as scaling and crumbling, is due to the pressure induced by the growing salt crystals from supersaturated solution inside pores [1]. So far, none of the existing solutions to improve the resistance of mortars to salt damage by changing their properties (e.g., using stronger binders or modifying water transport by the use of water‐
repellents) has been completely successful. In recent years, research has been undertaken aiming at influencing the crystallization behaviour by adding modifiers to the mortars instead of modifying the material properties [2]. The modifiers could prevent nucleation (inhibitors), promote nucleation of a certain crystal polymorph (promoters) and/or modify the habit of the crystals (habit modifiers). In this way, salt crystallization can be promoted rather at the surface of the material (efflorescence) than in the pores (crypto‐florescence). This might eventually result in a reduction of the damage. We have investigated the effectiveness of borax (Na2B4O7∙10H2O) as modifier of sodium sulfate, one of the most deleterious salts in buildings. The impact of different borax concentrations on conductivity and wetting properties of sodium sulfate solutions was measured using a Metrohm conductivity probe and the KRUSS apparatus. Furthermore, using direct imaging and optical microscopy [3,4], the nucleation, growth and crystallization pattern of sodium sulfate solutions in the presence of borax were followed in evaporating droplets on glass plates, at controlled temperature and relative humidity. The results were compared with the crystallization dynamics of each of the pure components (i.e., Na2SO4 and borax). Additionally, borax and sodium sulfate were crystallized consecutively (simulation of the situation in a mortar, where borax will already be present when salts enter the material), to observe any differences compared to experiments on mixtures. Our results show that the addition of borax increases the wetting properties of the salt solution (lower contact angle). The improvement of the spreading properties of the solution leads to a higher evaporation rate, which in turn promotes efflorescence. Furthermore, our experiments show how the addition of borax to sodium sulfate leads to changes in crystal morphology in comparison with pure salt solution. References:
[1] Espinosa-Marzal R.M, Scherer G.W., Accounts of chemical research, Advances in understanding damage
by salt crystallization. 43 (2010), 897–905
[2] Granneman S.J.C., Ruiz-Agudo E., Lubelli B., van Hees, R.P.J., Rodriguez-Navarro, C., Proceedings of
1st International conference on Ageing of Materials and Structures, Study on effective modifiers for
damaging salts in mortar , (2014), 604-611
[3] Shahidzadeh-Bonn N., Rafai S., Bonn D., Wegdam G., Langmuir, Salt crystallization during evaporation:
impact of interfacial properties, 24 (2008), 8599-8605
4 Shahidzadeh N, Schut M., Desarnaud J., Prat M., Bonn D., Scientific Reports, Salt stains from
evaporating droplets, 5 (2015), 10335.
S07-P08
Optimization of Cooling Crystallization of High Aspect Ratio Crystals in Batch and Continuous
Operations for Size and Shape Control
David Acevedoa, Zoltak K. Nagya,*
aSchool
of Chemical Engineering, Purdue University, West Lafayette, 47907, IN
The cooling crystallization for potassium dihydrogen phosphate (KDP) was optimized for: (a) batch
and (b) continuous process. A two-dimensional population balance model was solved considering secondary
nucleation, size independent growth, size independent dissolution and breakage. The breakage model was
obtained from literature in which it was assumed that the rate of breakage is proportional to the product of the
frequency and energy of the collisions between the crystals and the crystallizer and crystals will become prone
to breakage only when their aspect ratio exceeds a certain limit.1 A non-linear optimization problem was solved
via sequential quadratic programming in which the aspect ratio or mean size of the length direction was
considered as objective function. Previous work the trade-off between the achievable size and shape of
crystals for different classes of systems such as KDP while considering primary nucleation and growth.2
The temperature profile was considered as optimization variable for the batch scenario. The optimization
results demonstrated that temperature cycling can maximize the growth of both crystal dimensions while
minimizing the aspect ratio. Moreover, the continuous process considered is a multi-stage mixed suspension
product removal crystallizer and various configurations were considered in order to evaluate the various
possible optimal designs while considering the various types of mechanisms. The steady-state temperature at
each stage and average working volume were considered as optimization variables for the continuous
scenario. The shape and size of KDP were optimized for continuous and batch scenario in which the common
trade-off between the objectives was minimized or eliminated by considering multiple mechanisms.
Keywords: Optimization, Shape, Breakage, Continuous crystallization
References:
1. Sato, K.; Nagai, H.; Hasegawa, K.; Tomori, K.; Kramer, H.J.M.; Jansens, P.J. Two‐
dimensional population balance model with breakage of high aspect ratio crystals for batch crystallization. Chemical Engineering Science. 2008, 63:3271‐3278. 2. Acevedo, D. Nagy, Z.K. Systematic classification of unseeded batch crystallization systems for achievable shape and size analysis. Journal of Crystal Growth. 2014, 394:97‐105. S07-P10
Nanoconfined Crystal Growth investigated by Reflection Interference Contrast
Microscopy
Felix Kohler1*, Dag Kristian Dysthe1
1
University of Oslo, Sem Sælands vei 24, Oslo (Norway)
A crystal growing against a surface exerts a force. A good understanding of this growing force is
essential to describe the deformation of solids by stresses generated by crystallization. This is
particularly relevant for the comprehension of damage by crystallization in porous building
materials, which is of great economical importance and fundamental for methods that can help to
preserve our cultural heritage [1, 2]. In addition, the fundamental knowledge of these forces is
needed for geodynamic modelling that forms a basis for oil exploration and modelling of reservoir
compaction.
However, the exact behavior of the growth and the dissolution process in close contact to an
interface are still not known in detail. The crystallization, the dissolution and the transport of
material is mediated by a nanoconfined water film. In contradiction to some theoretical results,
which predict a smooth interface, some recent experiments have shown that the nanoconfined
growth surfaces are rough.
We use methods such as reflective interference contrast microscopy (RICM) for in situ observations
of NaClO3 crystals growing against a glass surface (Figure 1). In this study, brittle NaClO3 is used
instead of plastically deforming crystals such as halite [3]. In order to carefully control the
supersaturation of the fluid close to the crystal interface, we use a temperature regulated
microfluidic system (Figure 2). In combination with theoretical studies and Kinetic Monte Carlo
simulations we aim at providing more realistic descriptions of surface energies and energy barriers
which are able to explain the discrepancies between experiments and the current theory.
Figure 1. Corner of NaClO3 Crystal observed by RICM
Figure 2. Control of crystal growth in microfluidic cell.
The temperature T2 at the place of the observed crystal
is lower than in the rest of the system (T1
References:
[1] G. W. Scherer, Cement and Concrete Research, 34 (2004) 1613
[2] Flatt, R. J. , Caruso, F., Sanchez, A. S. A. and Scherer, G. W., Nature Communications, 5 (2014) 4832
[3] Sekine, S., Okamoto, A.,Hayashi, American Mineralogist, 96 (2011) 1012
S07-P12
Microfluidics for in situ study of growth of calcium carbonate
Lei Li1, Dag Kristian Dysthe1*
1
University of Oslo, SemSælandsvei 24, Oslo (Norway)
The controllable synthesis of calcium carbonate (CaCO3) growth has received much attention due to
its wide scientific and industrial applications such as paper, rubber, paint, etc. The growth of CaCO3
crystals depends significantly on the composition of the surrounding solution and on the types of
surface active molecules. [1]
We prepare CaCO3 crystals in a microfluidic cell by precipitation reaction of sodium carbonate with
calcium chloride in water. The fluid flow minimizes the effect of convection, diffusion and
turbulence due to concentration gradients. This leads to a highly controlled solution concentration
around the crystal and allows to study the growth behavior of calcium carbonate with high
resolution microscopy methods (Figure 1).For further analysis of the processes that appear in the
channel ex situ Raman spectroscopy and scanning electron microscopy have been performed in
addition.
A
B
Figure1. (A). Microfluidic network for crystal growth experiments with inlets for different fluids and outlet on right hand.
(B). Growth patterns of calcium carbonate for varying supersaturation. Bright field microscopy images performed on
Olympus GX71.
References:
[1] Anja R., Dag K.D., Journal of Crystal Growth, 346(2012) 89.
S07-P13
In-situ Raman technique applied to monitoring phase transition of linear alkylbenzene
sulphonate (LAS)
Boyang. Zou1*, Xiaojun Lai1, Dan Xu2 and Luis Martin de Juan2
1
University of Leeds, Leeds, LS2 9JT, United Kingdom
2 Procter
& Gamble, Newcastle Innovation Centre, Newcastle, United Kingdom
Linear alkylbenzene sulphonate is one of the main components included in powdered washing detergents
to help with stain removal. In aqueous solution it usually presents in a mixture of L1 (micelle phase) and La
(lamellar phase, liquid crystal) over of wide range of composition, see figure 1. In the process, LAS and other
various components are mixed into a slurry, thereafter pumped into a spray drying system. The physical and
chemical properties of the spray dried powder are greatly affected by the properties of the slurry; these are
essentially derived from the phase behaviours of LAS and the interactions among the different components
within the system [1].
Analytical techniques such as SAXS, XRD & DSC are used for LAS phase study. Yet, some of them are
either difficult to access or have high operating costs. Others are not suitable for liquid systems or require
sample preparation. In this study, In-situ Raman technique is used to measure LAS surfactant with the
advantages of requiring no sample preparation, less interference of aqueous media and run-time data output.
The effect LAS solution concentration, temperature and ionic strength have on phase composition and
transition is considered; these results show agreement with other research in this area [1]. Therefore, it can be
concluded that Raman spectroscopy has potential for use in the study of surfactants.
a
b
D - spacing
Spherical Micelle
Water layer
Cross section
Lamellar phase
Figure 1. a: LAS in 3 and 6 positional isomer[1];b: L1 (micelle phase) and La (lamellar phase, liquid crystal) structure
References:
[1] J. A. Stewart a , A. Saiani, et al., Journal of Dispersion Science and Technology. 2011. 32:12, 1700-1710.
S07-P14
Solubility studies of GaN in NH3/mineralizer-solutions
Thomas G. Steigerwald; Nicolas S.A. Alt; Anna-Carina L. Kimmel; Benjamin Hertweck; Eberhard
Schluecker;
Institute of Process Machinery and Systems Engineering, Friedrich-Alexander-University ErlangenNuremberg, Erlangen, Deutschland
For the crystallization of binary and multinary nitrides, amides and imides of
gallium, aluminum, silicon and germanium, the ammonothermal process is a
suitable approach. This solvothermal synthesis uses supercritical ammonia
atmosphere at temperatures up to 870 K and pressures of several hundred
megapascal to recrystallize nitrides [1]. In the figure a typical autoclave with
two temperature regions is shown, one region is the dissolution zone with a
feedstock and the other the recrystallization zone with seed crystals. A
defined temperature gradient between the two regions is needed, that
causes thermal convection in the apparatus. With a baffle the convection can
be adjusted specifically.
For good crystal quality it is important to recrystallize near the
thermodynamic equilibrium, which depends on the solubility of GaN in the
ammonia/mineralizer-mixture.
The synthesis takes place in thick walled autoclaves, which needs high
maintenance for every single experimental run [2]. As research is still in its
infancy, for every new precursor/mineralizer combination a lot of
gravimetrically analyzed measurements have to be done. In this talk, the
solubility curve of the GaN/NH4F/NH3-mixture is shown and reasons for the
high time and resource consuming determination are discussed.
One result is that solubility depends strongly on temperature. By the use of UV/Vis- spectroscopy it
is possibly to estimate a temperature and pressure range where solution of GaN in the
mineralizer/ammonia-mixture begins within a single experiment. In a custom-made optical cell the
GaN/NH4F/NH3-mixture is analyzed and it could be shown, that some intermediates were formed
at 550°C, which leads to a change in the wavelength of the irradiated light. Unfortunately this is
only qualitative and not quantitative approach. In polar solvents, like ammonia, the dissolving
capacity can be described by the dielectric constant. So as prospect for future research the
electrochemical impedance spectroscopy, as it was done by M. Buback et al. for pure ammonia [3],
shall be applied to ammonothermal systems to gather solubility data in a fast way. The challenge is
a high-pressure, high temperature electrical lead through with low thermal gradients. So some
technical drawings of a modified lead through are presented to fulfill these purposes.
[1] Ammonothermal Crystal Growth of GaN Using an NH4F Mineralizer, Q. Bao, et al., Crystal Growth & Design,
2013, 13, 4158-4161
[2] Ammonothermal crystal growth of gallium nitride – A brief discussion of critical issues, D. Ehrentraut, T. Fukuda,
Journal of Crystal Growth, 312 (2010) 2514-2518.
[3] The Static Dielectric Constant of Ammonia to High Pressures and Temperatures, M. Buback and W. D. Harder,
Berichte der Bunsen-Gesellschaft, 1977, 81 (6), 603-614.
S07-P15
Analysis of temperature data obtained by measurements of temperature field at
simulated vertical Bridgman crystal growth of PbCl2
Král Robert*1, Nitsch Karel1
1
Institute of Physics Czech Academy of Sciences, Cukrovarnicka 10, 162 00 Prague (Czech Republic)
Recently, a new method for a direct measurement of the temperature field during simulated
crystal growth of lead chloride (PbCl2) by the vertical Bridgman method has been developed [1].
This method allowed detail analysis of heat conditions in the system and determination of the
position and the shape of crystal/melt interface. The temperature field presented in this study at first
ampoule position, where there was more melt than the crystalline phase in the ampoule, in the steep
temperature gradient (35 K/cm) under stationary conditions (zero pulling rate) was measured by
four thermocouples. These thermocouples were placed in specially prepared quartz ampoule with
four asymmetrically positioned capillaries along the ampoule axis. The temperature field was
measured repeatedly four times. Obtained temperature data from all four thermocouples were
projected as 2D planar cut under radial symmetry and denoted as isolevels. However, their
conversion into isotherms by linear approximation for further analysis was required. Nevertheless,
only isotherms 500 °C corresponding to the melting point of PbCl2 lead to identification of the
position and shape of crystal/melt interface. Obtained temperature data were analyzed separately
and together by calculating an average temperature field. Standard deviation of this average
temperature field was evaluated and it was ca. 0.2 K in crystalline phase, 0.4 K in the melt, and 0.2
K in the atmosphere over the melt. Lower values of the standard deviation in the crystal and in the
atmosphere points to stable heat flow conditions in these phases than in the melt. On the contrary,
the higher standard deviation in the melt could be originated by the heat transport fluctuations
caused by changes in the melt buoyancy. Furthermore, first and second derivation of temperature
data in dependence on the vertical position in the ampoule measured by each thermocouple were
evaluated. The first derivation showed two maxima in vertical position at around 7 and 49 mm,
which were in agreement with both the vertical position of crystal/melt interface and melt surface
captured, when the ampoule was pulled out from the furnace during simulated crystal growth.
Moreover, the shape of the crystal/melt interface was determined by fitting the isotherms 500 °C
with a circle function using a least square method. The position of the circle center as well as its
radius were the key parameters determining if the shapes of the isotherm 500 °C were convex into
the melt, concave, or planar ones. This contribution deals with a statistical evaluation of measured
temperature data and continues in our previously presented work [1]. The goal of this work is to
find suitable growth conditions for preparation of high quality single crystals of lead halides and
ternary alkali lead halides considered to be suitable as hosts for mid-IR lasers [2].
Acknowledgment:
This work was supported by the Japan Society for the Promotion of Science (JSPS) Grant-in-Aid for
Exploratory Research (AY) for JSPS Postdoctoral Fellowship for Foreign Researchers (P14040) and Czech
project MEYS KONTAKT II, no. LH14266.
References:
[1] R. Král, J. Cryst. Growth 360 (2010) 162–166.
[2] R. Král, K. Nitsch, V. Babin, J. Šulc, H. Jelínková, Y. Yokota, A. Yoshikawa, M. Nikl, Opt. Mater. 36
(2013) 214–220.
S07-P16
Controlling Ice Growth Using Selective Infrared Radiation
Guy Shlomit*, Yashunsky Victor, Chayet Haim and Braslavsky Ido
Institute of Biochemistry, Food Science and Nutrition, Robert H. Smith Faculty of Agriculture, Food and Environment,
The Hebrew University of Jerusalem, Rehovot, Israel.
*[email protected]
Freezing is used to preserve cells, tissues and food for a long period of time. However, ice
formation during the preservation procedure can be destructive. For example, ice recrystallization is
an Ostwald ripening process, in which larger ice crystals grow on the expense of the smaller ones.
This process causes damages to food and biological systems, as a result of mechanical disruptions
by the growing ice crystals during freezing and thawing. To achieve a successful cryopreservation,
the formation of growing ice crystals must be controlled. This research examines the implication of
selective infrared (IR) radiation on ice and partially frozen systems. We propose to control and
manipulate ice growth using selective IR radiation, which is absorbed by the ice more efficiently
than by water. Using the selective radiation, we have found a unique ice pattern, in the shape of
holes and micro-channels. Pattern formation is found in nature in many scenarios, for example:
desert vegetation and skin color of animals, such as fish and zebras. Those patterns resulted from
processes of reaction-diffusion. We intend to use a reaction-diffusion model to explain the special
ice pattern that was observed in our system. The model will include the heat that is created by the
radiation and diffuses according to the temperature gradient. The temperature determines the phase,
which is also time dependent.
Based on these findings, we propose to combine ice binding materials, as they are used as a
known method to control ice growth. Antifreeze proteins and the synthetic material Zirconium
Acetate, by binding to an ice crystal, inhibit ice growth and depress ice recrystallization. They
possess ice shaping properties as well. We will investigate the selective radiation in combination
with ice binding materials as a method to control ice shaping, ice growth and recrystallization. The
ice growth modifications can be used to improve cryopreservation procedures.
Acknowledgements:
European Research Council (ERC)
Israel Science Foundation (ISF)
S07-P17
Electron Microscopy Studies of Growth and Structure of MoS2-based
Hydrodesulfurization Catalysts
Lars P. Hansen1, Erik Johnson2, Quentin M. Ramasse3, Christian Kisielowski4, Michael Brorson1 and Stig
Helveg*1
1. Haldor Topsøe A/S, Nymøllevej 55, DK-2800 Kgs. Lyngby, Denmark.
2. Nano-Science Center, Niels Bohr Institute, Universitetsparken 5, DK-2100, Copenhagen, Denmark.
3. SuperSTEM Laboratory, STFC Daresbury, Keckwick Lane, Daresbury WA4 4AD, United Kingdom
4. Lawrence Berkeley National Laboratory, National Center for Electron Microscopy and Joint Center for Artificial Photosynthesis, Berkeley CA 94708, United States of America.
Production of transport fuels with ultra-low sulfur contents in oil refineries requires very
efficient catalytic hydrodesulfurization processes. As new environmental legislation for clean fuels
demands an enhanced removal of sulfur and other impurities from mineral oil, attention is currently
being devoted to understand the catalysts’ structure-activity relationships.
In oil refineries, the hydrodesulfurization catalysts are based on highly anisotropic MoS2
nanocrystals as the active component [1,2]. It is well-known that the catalytic reactivity of the MoS2
nanocrystals is associated with their exposed edges, size and morphology. However, although
MoS2-based catalysts are synthesized at a very large scale in the refining industry, insight into the
structure and dynamics of the MoS2 nanostructures has remained a challenge to unveil.
Recent advancements have made (scanning) transmission electron microscopy (S/TEM) a
powerful technique for studying individual (supported) nanoparticles at the atomic-level [3-5]. In
this presentation, we demonstrate the application of such advancements for single atom sensitivity
and in situ electron microscopy of MoS2-based hydrotreating catalysts. By means of time-resolved
TEM imaging, the growth of MoS2 nanocrystals is monitored in situ during the sulfidation reaction
that transforms a molybdenum oxide precursor material into highly dispersed MoS2 nanocrystals
(Figure 1). Specifically, the time-resolved image series provide new information about the evolution
of MoS2 nanocrystals with different size, morphology and stacking and thus uncover the nucleation
and growth of the MoS2 nanocrystals. The in situ observations are beneficially combined with
single-atom sensitive imaging by S/TEM, and thus provide unprecedented new insight into the
formation of MoS2 nanocrystals with specific distribution of active sites.
Figure 1. (a) In situ sulfidation of molybdenum oxide precursor dispersed on a Mg-spinel support during exposure to 1
mbar H2S:H2 1:9 at 690 ºC. (b) High resolution STEM image of a region at the catalytically important edge of a MoS2
nanoparticle in (001) projection on a graphite support. [4,5]. References:
[1] H. Topsøe et al, Hydrotreating Catalysis, vol. 11, Springer, Berlin (1996).
[2] F. Besenbacher et al, Catal. Today, 130 (2008), p. 86.
[3] C. Kisielowski et al, Angew. Chem., Int. Ed. 49 (2010), p. 2708.
[4] L. P. Hansen et al, Angew. Chem., Int. Ed. 50 (2011), p. 1015
[5] L. P. Hansen et al., J. Phys. Chem. C 118 (2014), p. 22768
SESSION 8
Epitaxial Growth - Crystal Growth Interfaces
Analysis of critical thickness for generated misfit dislocation in GaInN/GaN
superlattice on GaN by in situ X-ray diffraction
Junya Ohsumi*1, Koji Ishihara1, Taiji Yamamoto1, Motoaki Iwaya1, Tetsuya Takeuchi1, Satoshi Kamiyama1,
and Isamu Akasaki1,2
1
Faculty of Science and Technology, Meijo University, 1-501 Shiogamaguchi, Tempaku-ku, Nagoya 468-8502, Japan
2
Akasaki Research Center, Furocho, Chikusa-ku, Nagoya University, Nagoya 464-8603, Japan
The GaInN/GaN superlattice (SL) structure is used as the active layer in commercially available
visible-light emitting devices. There are many interesting features that make these nitride
semiconductor alloys especially useful for efficient light emitters. In addition, these materials are
also useful as a high conversion efficiency solar cell. Most devices using GaInN/GaN SL are
fabricated on GaN, because the growth of thick GaInN films with high crystallinity on substrates
other than GaN is very difficult. Several studies have been previously conducted to elucidate the
mechanism by which defects form via strain relaxation in GaInN/GaN SL structures, because it is
necessary to minimize defect formation in order to improve device performance. However, current
understanding of the critical layer thickness at which misfit dislocations are introduced in
GaInN/GaN SL structures is insufficient. In this study, we observed the growth of the GaInN/GaN
SL structure by in situ X-ray diffraction monitoring.
The samples were grown on c-plane sapphire substrates using metalorganic vapor phase epitaxy
apparatus with a horizontal face down 2” × 3” reactor. After the growth of a 3-μm-thick GaN
template at 1,050 °C on c-plane sapphire covered with a
low-temperature GaN buffer layer using H2 carrier gas at
10
933 hPa, it was cooled to 750 °C and the carrier gas was
changed to N2. Then, GaInN/GaN SL structure was grown
10
on the GaN template. The threading dislocation density of
the GaN template was ~3 × 108 cm-2. We evaluated the
10
GaInN films with symmetric (0002) Bragg diffraction using
Single layer
an in situ XRD system. As the results, the satellite peaks
SL (only GaInN thickness)
from the -1st to the +1st order can be obtained from these in
10
0 .0
0 .1
0 .2
0 .3
situ X-ray diffraction spectrums. From the full width at half
InN molar fraction
th
st
maximums (FWHMs) of the 0 and -1 satellite peaks as a
function of the SL periods, we observed a clear trend in each Figure 1. Critical thickness of the
GaInN
thickness
in
FWHM. It was found that by analyzing this trend along with total
florescence microscopic and transmission electron GaInN/GaN SL and single GaInN
microscopic analysis, an analysis of the In segregation and layer as function of InN molar
misfit dislocation are possible. Accordingly, if we employ in
situ X-ray diffraction under various growth conditions, the optimization of the growth conditions
will become easier because it would be possible to determine the number of periods at which In
segregation and misfit dislocation increases by only one growth procedure.
We also investigated the thickness of this saturated FWHMs for various InN molar fractions
from the behavior of the FWHMs by in situ XRD measurements, as shown in Fig. 1. We also
compared our experimental results of single GaInN samples. From this figure, critical thickness of
GaInN and GaInN SL was almost same. In addition, we will discuss relaxation and surface state by
AFM, SEM, and XRD mapping.
Thickness (nm)
3
2
1
0
Acknowledgement This study was partially supported by the Program for the Strategic Research Foundation at
Private Universities, 2012–2016, supported by the Ministry of Education, Culture, Sports, Science and
Technology (MEXT) , a MEXT Grant-in-Aid for Specially Promoted Research #25000011, and the MEXT Grantin-Aid for Scientific Research A #15H02019.
In situ observation of low temperature growth of Ge on Si(111) via RHEED
Andreas Grimm*1, 2, Andreas Fissel1, Eberhard Bugiel1, H. Jörg Osten1, 2,3, and Tobias F. Wietler1 ,2 ,3
1
Institute of Electronic Materials and Devices, Schneiderberg 32, D-30167 Hannover, Germany
2
Hannover School for Nanotechnology, Schneiderberg 39, D-30167 Hannover, Germany
3
Laboratory of Nano and Quantum Engineering, Schneiderberg 39, D-30167 Hannover, Germany
The integration of Ge into existing silicon-based technology is the key approach to new
functionality extension of Moore´s Law. Ge provides the potential to combine photon based data
processing with Si complementary metal oxide semiconductor processing (CMOS). Epitaxial Ge
films enable a monolithic integration of optoelectronic devices into silicon-based technology. Ge
used as buffer system, is a candidate for III-V integration on Si. Having strong light absorption in
near-infrared wavelength range as well as a pseudo-direct band gap behaviour [1] Ge-based Laser
systems or Ge photodetectors can be achieved [2,3]. The pseudo-direct band gap behaviour is only
observed in tensile strained Ge films, which makes precise control of growth parameters and strain
engineering necessary.
Growth processes in MBE can be analysed and controlled using reflection high energy electron
diffraction (RHEED). RHEED is the most widespread method for in situ analysis of thin film
surface structure and provides an opportunity for real time observation of epitaxial growth. The
initial stages of Stranski-Krastanov growth mode of Ge on Si(111) were investigated by Ichikawa
and Ino [4] for a wide range of temperatures (from RT on with subsequent heating). Deelman et al.
added in situ strain relaxation studies of Ge epitaxy on Si(111) for temperatures from 450 °C up to
700 °C [5,6].
Here, we investigate Ge epitaxy on Si(111) using RHEED in a growth temperature regime of
200 °C to 400 °C with growth rates ≈ 1 ML/min. The different stages of Stranski-Krastanov growth
mode, i.e. wetting layer formation and subsequent islanding, are identified via spot intensity
analysis [7]. With increasing Ge layer thickness strain is accumulated due to the lattice mismatch of
4.2% to Si. At a certain critical thickness dc, the film minimizes its total energy via elastic and
plastic relaxation. Elastic relaxation proceeds via island formation whereas plastic relaxation is
obtained by introduction of misfit dislocations. Hence, we obtained information about the critical
layer thickness at low temperatures. The critical thickness dc for the inset of elastic/plastic
relaxation is determined by spot intensity analysis to 3.1 < dc < 3.4 ML and is in good agreement
with thermodynamic considerations.
Additionally, RHEED provides in situ access to the degree of strain relaxation. The strain
relaxation process is qualitatively made visible and corroborates spot intensity analysis (inset of
relaxation around 3 ML ± 0.5 ML). The relaxation of grown Ge islands is verified by ex situ
Transmission Electron Microscopy (TEM) investigations, which show partially relaxed Ge islands.
An ordered dislocation network is already visible at growth temperatures of 200 ˚C.
References:
[1] C. van de Walle, Phys. Rev. B 39 (1989) 1871.
[2] S. Wirths, R. Geiger, von den Driesch, N., G. Mussler, T. Stoica, S. Mantl, Z. Ikonic, M. Luysberg, S.
Chiussi, J. M. Hartmann, H. Sigg, J. Faist, D. Buca and D. Grützmacher, Nature Photon 9 (2015) 88.
[3] J. Liu, R. Camacho-Aguilera, J. T. Bessette, X. Sun, X. Wang, Y. Cai, L. C. Kimerling and J. Michel,
Thin Solid Films 520 (2012) 3354.
[4] T. Ichikawa and S. Ino, Surface Science 136 (1984) 267.
[5] P. W. Deelman, T. Thundat and L. J. Schowalter, Applied Surface Science 104-105 (1996) 510.
[6] P. W. Deelman, J. Vac. Sci. Technol. A 15 (1997) 930.
[7] K. Miki, K. Sakamoto and T. Sakamoto, MRS Proc. 148 (1989) 323.
Structural and electrical characteristics of AlGaN/GaN heterostuctures with
thin AlN interlayer on sapphire substrate grown by MOCVD
Raju Ramesh*1, 1Kandasamy prabakaran 1 ,Ravi Loganathan1, 2Manavaimaran Balaji2, Eric Faulques3,
Alexandre CRISCI4,Krishnan Baskar1
1
Anna University,Crystal Growth Centre, Chennai,India
Madras University, Centre for Nanoscience, Chennai, India
3
AffInstitut des Matériaux Jean Rouxel, Université de Nantes,France
4
Ingénieur d'études, CNRS, Laboratoire SIMaP,France
2
Thin AlN interlayers are widely used in (Al,Ga)N based high-electron-mobility transistors
(HEMT) to improve the mobility of the two-dimensional electron gas forming at the
GaN/(Al,Ga)N interface.[1,2]. AlGaN/GaN heterostructure with thin AlN inter layers (IL) of 1 to 3
nm thickness were grown on 2”c-plane sapphire substrates by metalorganic chemical vapour
deposition. The structural, optical and electrical quality of epilayers have been characterized by
high-resolution X-ray diffractometer (HRXRD), atomic force microscopy (AFM),
photoluminescence spectra (PL), Raman scattering spectrometer and Hall measurement. The AlNIL is believed to have a direct influence to improve the quality of the AlGaN epilayer. Upon
optimizing AlN-ILthickness at 3 nm a high crystalline quality with a full width at half maxima
(FWHM) for the (0002) and (10-12) planes of GaN as 373 and 672 arc-sec, respectively has been
achieved. The AlGaN epilayer also revealed atomic level step with a root mean square (RMS)
roughness of 0.16 nm (figure. 1a). In Raman spectra, the mode at 748 cm-1is attributed to the
A1(LO) mode of AlGaN and AlN-IL effects. The 2DEG concentration has been found decrease
from 1.2 x1013 cm-2 to 9.8 x1012 cm-2 on increasing the AlN-IL thickness. On the other hand, the
mobility of 2DEG was found to be increased
(figure 1.b) The structural and electrical
properties of AlGaN/GaN HEMTs with AlN-IL were characterized and the results have been
discussed in detailed.
a
b
Figure 1.(a) AFM images on the surface of AlGaN/GaN with 0-3 nm AlN interlayer (b)Hall mobility from 80K to 350 K
References:
[1] Haoran Li., Stacia Keller., Silvia H Chan., Jing Lu., Steven P DenBaars and Umesh K Mishra Semicond.
Sci. Technol., vol. 30 (2015), PP.055015 (7pp).
[2] Tülek, R, Ilgaz, A, Gökden, A, Teke, A, Öztürk, M. K, Kasap, M & Özbay, E 2009, Journal of Applied
Physics, vol. 105, no. 1, pp. 013707.
Two-dimensional Si/Si(111)-(7×7) nucleation
affected by step permeability and sink to atomic steps
Rogilo Dmitry*1,2, Fedina Liudmila1,2, Kosolobov Sergey1,2, Ranguelov Bogdan3, Latyshev Alexander1,2
1
Institute of Semiconductor Physics, pr. Lavrentieva 13, Novosibirsk (Russia)
2
Novosibirsk State University, Pirogova Str. 2, Novosibirsk (Russia)
3
Institute of Physical Chemistry, Bonchev Str. 11, Sofia (Bulgaria)
The two-dimensional nucleation and growth (2DNG) of Si is studied by in situ ultrahigh
vacuum reflection electron microscopy (UHV REM) on the step-bunched Si(111)-(7×7) surface
( 10 μm wide terraces) and on extra-large (~100 μm) step-free terraces at 600–750°C. In both
cases, the epitaxy starts with classical 2DNG. However, after Θ~100 ML Si deposition we observed
the formation of pyramid-like waves in the former case (Fig. 1a) and many separate triangular
pyramids in the latter case (Fig. 1b).
We used the 2DNG on the step-bunched surface to obtain the dependences of both 2D island
concentration N2D and critical top layer width λ on sample temperature T, deposition rate R, and
initial terrace width. From the analysis of λ2(T,R) scaling we have detected at T≈720°C the
transition from the diffusion limited growth kinetics to the kinetics limited by 0.9 eV barrier for the
preferential attachment to descending steps [1]. We attribute this barrier to the impeded double kink
-type faceted step edges that provides the triangular faceting and the
nucleation at
permeability of steps. When comparing the λ2(R) and the N2D(R) dependences, we first show that
the kinetically limited sink of adatoms to descending permeable steps causes downhill adatom
current and the increase of critical nucleus size i by up to 10 times at the top layer of the pyramidlike waves.
In contrast to the step-bunched surface, Si deposition (Θ≈300 ML) onto the extra-large step-free
terraces leads to the formation of many separate triangular pyramids (Fig. 1b). Based on the linear
slope of pyramids’ layer coverage distribution (Fig. 1c), we conclude that the formation of pyramids
at the step free surface is caused by the destabilizing net uphill adatom current triggered by
-type island edge permeability in accordance with modern theoretical conceptions [2, 3].
The work is partially supported by projects of RFBR (No. 14-02-31440), MESRF
(No. 14.621.21.0004), and RSF (No. 14-22-00143).
Figure 1. Si(111)-(7×7) surface morphology after prolonged Si deposition:
(a) a pyramid-like wave formed on the step-bunched surface,
(b) triangular pyramids formed on an extra-large step-free surface, and (c) its layer coverage
distribution
References:
[1] Rogilo D., Fedina L., Kosolobov S., Ranguelov B., Latyshev A., Phys. Rev. Lett., 111 (2013) 036105
[2] Hervieu Yu., Markov I., Surf. Sci., 628 (2014) 76
[3] Korutcheva E., Koroutchev K., Markov I., Eur. Phys. J. B, 86 (2013) 60
Epitaxial growth of Ge/Si nanostructures on Si surface patterned by ion
irradiation
Zh.V. Smagina*1, A.V. Zinovyev1, N.P. Stepina1, A.F. Zinovieva1, S.A. Rudin1, P.L. Novikov1,2, V.A. Seleznev1,
A.V.°Dvurechenskii1,2
1
Institute of Semiconductor Physics SB RAS, Lavrentjeva 13, Novosibirsk, 630090 (Russia)
2
Novosibirsk State University, Pirogova 2, Novosibirsk, 630090 (Russia)
Self-assembled Ge quantum dots (QD) on Si(100) have been intensively investigated as the
basis of novel electronic and optical devices. The space-ordered arrays of Ge QDs with little
dispersion of size are generally required for any practical applications. Many research groups work
at the development of methods of ordered structures fabrication. In this work we have proposed a
method of Ge QDs growth on prepatterned Si substrates obtained by a combination of nanoimprint
lithography and ion irradiation. The original idea of the selective etching of irradiated Si domains
was used to create the periodically stripped structure (80 nm-wide trenches, 100 nm-wide
interspacing (ridges) on Si with relief height varyied from 10 to 80 nm. The shape and depth of the
relief was controlled by the proper choice of ion dose and energy as well as by the number of
etching steps [1]. It was found that during the heteroepitaxy of Ge on a prepatterned Si(100) surface
the Ge nanoislands are arranged as linear chains on the ridges, if the trench depth is in the range of
15-30 nm, which is smaller than the projected ion range. The nanoislands grow inside trenches in
the case of deep etching, during which radiation defects are removed almost completely. The island
density and size strongly depend on the substrate temperature and deposition rate during epitaxy.
The optimal temperature and deposition rate at which we obtain most homogeneous nanoislands
arrays are 600°С and 0.1 ML/c, respectively. This method was used to create multilayer nanocluster
structures, representing three-dimensional crystals of quantum dots in a crystalline matrix.
Chemical content, structure and electronic properties of the grown structures were studied by
Raman scattering, high resolution electron microscopy and photoluminescence (PL). Intensity of PL
of structures with space-arranged islands was found to be three times greater than that in the case of
randomly located islands. Transport measurements were carried out for the current lines oriented
along or perpendicular to the dot chains. Strong anisotropy of the conductance was observed
indicating one-dimensional (1D) character of electron transport. At low bias voltages the charge
transport is described by Arrhenius law typical for 1D conductance and is determined by crucial
role of highly resistive segments on the conducting paths. An evidence of line ordering of QDs was
obtained from electron spin resonance (ESR) spectra. Recently it was found that the ESR line width
is broadened with deviation of magnetic field from the growth direction for structures with nonordered QDs [2]. This case is typical for Dyakonov-Perel spin relaxation, which is due to the
random walk of electrons in the plane. In the case with ordering of dots along lines the directions of
electron hops are not random, therefore we don’t observe the broadening of the ESR line width. The
microscopic mechanism of atom diffusion on a prepatterned surface and growth of Ge/Si structures
were studied by molecular dynamics and Monte Carlo simulations. The analysis has shown that
introduction of ion-irradiation-induced interstitial atoms leads to the suppression of island
nucleation inside trenches. The work was supported by RFBR (Grant 13-02-01181, 13-02-00901).
References:
[1] Smagina Zh.V., Stepina N.P., Zinovyev V.A. et al., APL, v. 105 (2014), p. 153106.
[2] Zinovieva A.F., Dvurechenskii A.V., Stepina N.P. et al., Phys. Rev. B, v. 77 (2008), p. 115319.
Self-assembled strained GeSi nanoscale structures grown by MBE on Si(100)
Alexandr Nikiforov1, 2, Vyacheslav Timofeev1, Artur Tuktamyshev1, Michail Esin1, Serge Teys1, Oleg
Pchelyakov1, 2
1
A.V. Rzhanov Institute of Semiconductor Physics SB RAS, Lavrentjeva 13, 630090 Novosibirsk, Russia
2
National Research Tomsk State University, Lenin Prospect 36, 634050 Tomsk, Russia
Nanostructures are particularly important objects in the nano - and optoelectronics. The basic
materials investigations have focused on the modification of the material to improve its optical and
electronic properties in order to realize the efficient light emitting or absorption [1].
The experiments have been carried out by a molecular beam epitaxy (MBE) installation
“Katun”. Ex situ scanning tunnel microscopy (STM) with an ultrahigh vacuum instrument
“Omicron-Riber” was used for the observation of the surface morphology.
The difference in surface energy for the strained planes of Ge(100) and Ge(105) is sufficiently
small, hence the islands with {105} facet (hut-islands) are energetically more favorable in the lowtemperature range as compared with the dome-islands which contain the facets with the surface
energies significantly greater than the strained face of Ge(100). On the other hand, dome-islands are
energetically more stable than the hut-islands due to the greater degree of the strain relaxation. At
high temperatures, the value of the anisotropy becomes smaller due to the increase of the entropy
and thereby the barrier lowers to the formation of dome-islands.
By forming of the thin Ge wetting layer and the subsequent annealing process we have obtained
nanowires which were observed at the annealing temperature of 450°C. In the beginning the Ge
film grows at the temperature of 500°C then the temperature of the substrate is reduced and this
layer is annealed for 10 hours (figure 1). The Ge thickness corresponds to the wetting layer with the
accumulated elastic strains. The surface morphology of the Ge layer have been demonstrated in
figure 4. We have carried out our experiments in the wide range of annealing temperatures of 300650°C. The same structures containing nanowires were obtained by Zhang et al. [2].
The work is supported by the RFBR ( Projects 14-29-07153) and by The Tomsk State
University Academician D.I. Mendeleev Foundation Program (Research grant No 8.2.10.2015).
Figure 1. STM image (400x400 nm) of Ge film after 10 h annealing at 450oC.
References:
[1] A.I. Yakimov, A.I. Nikiforov, V.A. Timofeev et al., Semicond. Sci. Technol. 26, 085018 (2011).
[2] J.J. Zhang, A. Rastelli, O.G. Schmidt et al., Appl. Phys. Lett., 103, 083109 (2013).
Quantum dot chains in InAs/GaAs multistacked structures grown by MBE: a
strain analysis by FEM
Latini Valerio*,1, Placidi Ernesto1,2, Arciprete Fabrizio1, Magri Rita3, Patella Fulvia1
1
Dipartimento di Fisica, Università di Roma Tor Vergata, Via della Ricerca Scientifica 1, 00133, Roma (Italy)
2
CNR - Istituto di Struttura della Materia, Via del Fosso del Cavaliere 100, 00133 Roma (Italy)
3
Dipartimento di Fisica, Università degli Studi di Modena e Reggio Emilia and Centro S3 CNR - Istituto di
Nanoscienze, Via Campi 213/A, 41100 Modena (Italy)
A great interest in controlling the positions of Quantum Dots (QDs) over substrates has widely
arisen over the last decades, because of its potential in the fields of quantum information and
sophisticated optoelectronic devices [1]. Advances in the fabrication of ordered QD arrays have
been obtained by combining bottom-up and top-down methods before and/or after the epitaxial
growth. The bottom-up methods allow reaching higher crystalline quality and reducing the cost of
processing; on the other hand they require the capability of closely tailoring the growth processes.
Three-dimensional stacking of self-assembled QDs in multilayer structures provides an efficient
tool to control both the vertical and lateral arrangement of QDs in several systems. In the case of
we have shown [2] an innovative way to induce the self-assembling of chains of
InAs/GaAs
InAs QDs parallel to the
direction over mounded GaAs surfaces, even from the first QD
layer.
samples in a Molecular Beam Epitaxy
In this work, we grew multilayer InAs/GaAs
(MBE) chamber under critical growth conditions [2] and we observed the occurrence of distanced
direction over mounded surfaces [3].
sets of ordered n-fold parallel chains of QDs along the
We measured the in-line distances along the QD chains to study the correlation among them. The
shape of the in-line distance distributions suggested a progressive ordering of the QD positions with
average distance of about 75 nm, as the number of layers was increased.
In order to deepen our understanding of the QD arrangement, a sequence of several stacked
layers was modelled to simulate an experimental InAs/GaAs(001) multilayer. The COMSOL
Multiphysics package was used as a Finite Element Method (FEM) solver for the stress–strain
equations of the elasticity theory and to predicting the favourable locations where the InAs QDs of
the next layer are positioned [4]. The standard deviation relative to the average distance was
assumed as the reference parameter to evaluate the in-line ordering of QDs. The simulated data
showed a decreasing behaviour of the that is similar to the experimental trend, confirming a
tendency to the in-line ordering of the QDs as a function of the number of layers. On the other hand,
further FEM simulations revealed that the strain driving force seems to be insufficient to reduce the
QD displacement from the line.
We concluded that the strain field of the buried QDs plays a crucial role in rendering the in-line
distances between the QDs uniform, whereas the alignment of the single QD chain is mainly related
to the morphological features of the rippled surface.
References:
[1] Petroff P. M., Advanced Materials, 23 (2011) 2372
[2] Arciprete F., Placidi E., Magri R., Fanfoni M., Balzarotti A., Patella F., ACS Nano, 7 (2013) 3868
[3] Placidi E., Arciprete F., Latini V., Latini S., Magri R., Scuderi M., Nicotra G., Patella F., Applied Physics
Letters, 105 (2014) 111905
[4] Latini V., Placidi E., Arciprete F., Patella F., Journal of Crystal Growth, 419 (2015) 138
A study of -Ga2O3 hetero-epitaxial layers grown by MOCVD and ALD
F. Boschi 1, M. Bosi2, E. Buffagni2, T. Berzina2, C. Ferrari2, R. Fornari 1
1
Dept. of Physics and Earth Sciences, Univ. of Parma, Area delle Scienze 7/A, 43124 Parma (Italy)
2
CNR-IMEM Institute, Area delle Scienze 37/A, 43124 Parma (Italy)
In the past few years semiconducting sesquioxides, and especially -Ga2O3, attracted renewed
attention as large single crystals and high-quality homo- and hetero-epitaxial layers became
available, which resulted in novel electronic devices. Motivated by these exciting developments, we
recently started an activity on deposition and study of Ga2O3 on c-oriented sapphire. To this
purpose, we refurbished an MOVPE reactor in order to allow the use of water as oxidizing agent.
The reactor can be used either for standard MOCVD process or for atomic layer deposition (ALD)
by alternating the oxygen and gallium supply. The principal advantage of ALD consists in enabling
the growth of high-quality films at lower temperature.
When using MOCVD, the morphology and structural perfection of the hetero-epitaxial films
was seen to strongly depend on deposition temperature and partial pressure of the reagents. Up to
550 °C the layers were smooth and featureless but practically amorphous, whilst films grown at
temperatures of 650 °C were again smooth (see Fig. 1, Atomic Force Microscopy image, also
confirmed by SEM) but exhibited very distinct X-ray peaks, which were unambiguously ascribed to
-Ga2O3. X-ray measurements confirmed that the Ga2O3 films are (-201) oriented as previously
reported, which means that (-201) planes of the monoclinic structure lie parallel to the basal plane
of the hexagonal sapphire substrate. Often the rocking curves showed that the diffraction peaks
were shifted with respect to the expected angles. In a sample grown at 715 °C the peaks actually
occupied their nominal positions but were broader. At present, we do not have a univocal
interpretation of this feature, even if strain and defects, and possibly film stoichiometry, are
certainly involved.
On the other hand, the ALD layers appeared to be single crystalline and exhibited good X-ray
diffraction profiles already at deposition temperature of 550 °C, although the peak shift observed in
MOCVD epilayers was still present.
In this paper, we shall present our experimental results and compare the main properties of Ga2O3 epilayers prepared by ALD and MOCVD.
Figure 1: AFM picture of the surface of Ga2O3 film deposited at 650 °C, thickness 300 nm;
the scan on the right hand side shows that the roughness is ± 2nm.
Step density waves on vicinal crystal surfaces
Bogdan Ranguelov, Stoyan Stoyanov
Institute of Physical Chemistry, Bulgarian Academy of Sciences, 1113 Sofia (Bulgaria)
We present a new idea of an instability of a vicinal crystal surface at growth or evaporation
with fast moving steps. Our treatment is going beyond the quasi-static approximation used in the
classical crystal growth model of Burton, Cabrera and Frank, where the basic assumption is that the
steps move slowly. In contrast, we study crystal growth and evaporation phenomena in the case of
very fast surface diffusion of adatoms and taking into account the time dependence of the adatom
concentrations on terraces with different sizes. The new type of instability forms a traveling step
density waves on the vicinal crystal surface and it is presented when the step velocity exceeds a
specific critical value, related to the strength of the repulsion between individual steps (a possible
situation in MBE growth experiments). This instability is caused solely by the high velocity of the
step motion in contrast to the step bunching instability, where the surface is destabilized by surface
adatom electromigration, impurities or Erlich-Schwoebel effect.
Figure 1. Model view of the vicinal crystal surface with straight steps – evaporation, step kinetic
coefficient, electromigration force and step permeability
Our model is extended by taking into account the electromigration effect (F) and step
permeability (P) both in the cases of growth or evaporation of the vicinal crystal surface (Figure 1).
We show that the interplay between step velocity, electromigration and step permeability produces
a variety of spatial and temporal surface instability patterns. The presentation is accompanied by an
unique real time reflection electron microscopy movies of surface instabilities on Si(111) at
different temperatures and growth regimes.
References:
[1] Ranguelov B., Stoyanov S., Phys. Rev. B 76, 035443 (2007)
[2] Ranguelov B., Markov I., Cent. Eur. J. Phys. 7 (2), (2009), 350 – 355
[3] Chernov A. A., J. Crystal Growth 264 (2004), 499
Structural study of the innovative 3C-SiC/Si/3C-SiC/Si heterostructure for
electro-mechanical applications
R. Khazaka1,2, J.F. Michaud1, P. Vennéguès2, D. Alquier1 and M. Portail2
1
Université François Rabelais, Tours, GREMAN, CNRS-UMR 7347, 16 rue Pierre et Marie Curie, BP 7155, 37071
Tours Cedex 2, France
2
CRHEA, CNRS-UPR10, rue Bernard Gregory, 06560 Valbonne, France
The cubic silicon carbide (3C-SiC) is an interesting wide band gap material with outstanding
properties, very promising for designing Micro-Electro-Mechanical Systems (MEMS) devices
operating in harsh environment where Si-based devices reveal a shortage in their performance.
Furthermore, 3C-SiC can be heteroepitaxially grown on low-cost substrates, as silicon. This is of
interest for taking benefit from the SiC properties conserving a reduced development cost. Of
course, the successful development of a 3C-SiC/Si based sensor family is largely conditioned to a
good management of two major issues related to the large lattice mismatch as well as the large
thermal coefficient expansion mismatch between Si and SiC which make the growth of SiC on Si
and the reverse, i.e. Si on SiC, a real concern. That is a reason why if the prime growth of 3C-SiC
on Si substrates is well documented, the further growth of stacked 3C-SiC/Si structures on a Si
substrates, of high potential for designing original resonant structures, is, by far, less discussed.
In this presentation, we will give at first a general overview on this topic as well as on the
potential applications that this heterostructure can offer. In a second time, we will present an
extended structural investigation of a complete 3C-SiC/Si/3C-SiC heterostructure grown on a
Si(001) substrate by means of chemical vapor deposition (CVD). We will underline the specific
growth mode of each level of the structure.
Indeed, starting from a [001] oriented 3C-SiC epilayer, we observe a successive rotation of the
growth direction. The Si epilayer is grown along the [110] direction while the top 3C-SiC layer is
grown along the [111] axis. This switch in growth direction is interesting from fundamental as well
as applications point of view since the material properties is directly linked to the orientation. The
inclusion of hexagonal silicon is also observed in this structure. Finally, the antiphase domains in
the first 3C-SiC layer has been proved to be responsible on the domains formation in silicon
epilayer [1]. These domains in the Si epilayer induces the rotation of the domains in the subsequent
3C-SiC epilayer. All these points will be discussed both from a fundamental point of view and
within a more practical point of view of their interest for MEMS applications.
Figure 1. Cross-section TEM image of the
3C-SiC/Si/3C-SiC/Si heterostructure and
high resolution TEM images for the
Si(110)/3C-SiC(001) and
3C-SiC(111)/Si(110) interfaces.
References:
[1] R. Khazaka, M. Portail, P. Vennéguès, D. Alquier, J.-F. Michaud, Acta Materialia (2015)
(submitted).
Functionalization of SiC Nanowires by Supersonic Molecular Beams for
Photodynamic Therapy
Tatti Roberta*1, Aversa Lucrezia1, Verucchi Roberto1, Fabbri Filippo2, Rossi Francesca2, Attolini Giovanni2,
Bosi Matteo2, Salviati Giancarlo2 and Iannotta Salvatore2
1
IMEM-CNR Institute, Via alla Cascata 56/C, Povo (Italy)
IMEM-CNR Institute, Parco Area delle Scienze 37/A, Parma (Italy)
2
Photodynamic Therapy (PDT) is a therapeutical approach in the cancer treatment, which
consists in the activation of a photosensitizer (phorphyrins) with visible light in order to produce
singlet oxygen, to exert a cytotoxic activity towards cancer cells. The use of visible light limits the
PDT application only to shallow deseases, for this reason we propose a new “X-Ray induced PDT”
approach, using nanohybrid systems as photosensitizer, consisting in Silicon Carbide (SiC)
nanowires (NWs) functionalized with organic molecules (fluorinated porphyrins). Modification of
the inorganic semiconductor surface with organic or bio-molecules represents the route to activate
processes at the interface and can be achieved by functionalizing the SiC NWs with porphyrins, that
showing a good match between the organic absorption Q band and the 3C-SiC near-band-edgeoptical emission. In fact SiC NWs have interesting light emission properties [1] so it is promising
the idea to couple this light emission with an organic absorber showing strong fluorescence
properties, a viable route to increase the optical emission efficiency as well as to promote the
anchoring of biological groups. We demonstrated the functionalization of SiOx/SiC core shell NWs,
grown by a carbothermal method, showing enhanced fluorescence, with fluorinated porphyrins
H2TPP(F) by supersonic molecular beam deposition (SuMBD), an approach that can promote and
activate chemical/physical processes at the interface by means of the organic precursor kinetics
properties [2]. The H2TPP(F)/SiC-NWs system has been deeply investigated in-situ with surface
photoelectron spectroscopy and ex-situ by Cathodoluminescence (CL) to clarify the growth kinetics
at low coverages and the interface processes. Results concerning the core level (C1s, Si2p, N1s,
F1s) analysis at different growth steps on planar oxidized surface and SiOx/SiC core shell NWs will
be presented. The role of morphology of inorganic surfaces together with kinetic activation of
H2TPP(F) molecules in molecular beams will be discussed.
References:
[1] F. Fabbri, F. rossi, G. Attolini, G. Salviati, S. Iannotta, L. Aversa, R. Verucchi, M. Nardi, N. Fukuta, B.
Dierre, T. Sekiguchi, Nanotechnology, 21 (2010) 345702.
[2] M. Nardi, R. Verucchi, R. Tubino, S. Iannotta, Phys. Rev. B, 79 (2009), 125404.
Characterisation of sub-micrometer yttrium iron garnet LPE films with low
ferromagnetic resonance losses
Dubs Carsten*1, Surzhenko Oleksii1, Linke Ralf1, Jauß Thomas2, Danilewsky Andreas2
1
2
INNOVENT e.V., Technologieentwicklung, Prüssingstraße 27B, 07745 Jena (Germany)
Institut für Geo- und Umweltnaturwissenschaften, Albert-Ludwigs-Universität Freiburg, Hermann-Herder-Str. 5,
79104 Freiburg (Germany)
Single crystalline yttrium iron garnet (YIG), which is a magnetic insulator with the smallest
known magnetic relaxation parameter, appears to be a superior candidate for particle-less
information transport and processing in spintronic or magnonic devices. As bulk or thick film
material which is commonly grown by the liquid phase epitaxy (LPE) it has a very low damping
constant, allowing magnons to propagate over distances exceeding several centimetres. But YIG
functional layers and microstructures should be nanometre-thick with extremely smooth and perfect
interfaces and perfect epitaxial quality. Therefore, high-quality thin YIG films were grown using
different growth techniques such as magnetron sputtering, pulsed laser deposition and liquid phase
epitaxy to investigate spin-wave effects [1-4, design YIG waveguides 5 as well as
microstructures 6 for spin-wave excitation and propagation.
In this report microstructural as well as magnetic properties of 100 nm thin YIG and La:YIG
LPE films grown on (111) GGG substrates were presented. Surface roughness, crystalline
perfection and compositional homogeneity were investigated by atomic force microscopy, highresolution X-ray diffraction and X-ray photoelectron spectroscopy (XPS). Using argon-ion etching
technique XPS depth profile analysis exhibit a steep transition between epitaxial film and substrate
without broad interdiffusion layer.
Magnetic hysteresis loops obtained by vibrating sample magnetometry show for all YIG and
La:YIG films a magnetic anisotropy which is close to the ‘easy plane’ type with a typically in-plane
coercive field of only 0.1 Oe. The in-plane dc-magnetized films over stripline exhibit sharp
Lorentz-like absorption peaks near the frequency of ferromagnetic resonance (FMR) measured by
vector network analyzer. The FMR linewidth at 6.5 GHz is estimated ΔHFWHM = 1.3 Oe that is, to
our knowledge the narrowest value reported so far for YIG films with thicknesses of about 100 nm.
The Gilbert damping value extracted from frequency dependent measurements were α = 1.6  10-4
which is lower than recent other reports 1-6.
To compare sub-micrometer LPE films with state-of-the-art YIG films grown by gas phase
epitaxial techniques key properties were compiled to show the potential of the LPE technology for
sub-micrometer iron garnet film application.
References:
1 T. Liu, H. Chang, V. Vlaminck et al., JAP 115, (2014) 17A501
2 M.C. Onbasli, A. Kehlberger, D.H. Kim et al., APL Materials 2, (2014) 106102
3 C. Hahn, G. de Loubens, O. Klein et al. Physical Review B 87, (2013) 174417
4 N. Vliestra, J. Shan, V. Castel et al., APL 103, (2013) 032401
5 O. d`Allivy Kelly, A. Anane, R. Bernard et al., APL 103, (2013) 082408
6 P. Pirro, T. Brächer, A.V. Chumak et al., APL 104, (2014) 012402
Liquid phase epitaxial growth of GdAP and GdLuAP scintillating films
for synchrotron imaging
Riva Federica *1,2, Douissard Paul-Antoine 1, Martin Thierry 1, Zorenko Yuriy 3, Petrosyan Ashot 4, Dujardin
Christophe2
1
2
ESRF - The European Synchrotron, 71, Avenue des Martyrs Grenoble (France)
ILM - Institute Lumière Matière, Université Claude Bernard Lyon 1 - CNRS, UMR 5306, Université de Lyon,
F-69622 Villeurbanne Cedex (France)
3
Institute of Physics, Kazimierz Wielki University in Bydgoszcz, 85-090 Bydgoszcz (Poland)
4
Institute for Physical Research, Armenian National Academy of Sciences, 378410 Ashtarak-2 ( Armenia)
*[email protected]
Single crystal thin film scintillators are the state-of-the-art for 2D high-spatial resolution Xray imaging detectors. The visible image generated by a scintillator hitted by the X-rays is
magnified by microscope optics and projected onto an imaging sensor [1,2]. At low X-ray
energies, if a good combination of scintillator thickness, optics numerical aperture and
pixel size is chosen, the spatial resolution of such a detector is only diffraction limited.
Increasing the X-ray energy not only these kind of detectors suffer from low efficiency due
to the low absorption in the scintillating thin film, but also the spatial resolution is limited by
the spread of the energy deposition in the scintillator.
Our work is related to the development by liquid phase epitaxy of single crystal thin films to
improve the efficiency and the spatial resolution at high X-rays energy: new scintillators
with higher absorption or higher conversion efficiency are good candidates.
Aluminum perovskites present high densities and high effective atomic numbers. In
particular gadolinium aluminum perovskite GdAlO3 (GdAP) and lutetium aluminum
perovskite LuAlO3 (LuAP) are interesting because of their absorption k-edges located in an
energy range now commonly required for synchrotrons experiments [3]. To the best of our
knowledge, GdAP cannot be produced from bulk techniques with good optical quality on a
large area, therefore we choose single crystal commercial YAP as substrates. We studied
the condition of crystallization of GdAP and GdLuAP (GdxLu1-xAlO3) thin heteroepitaxial
films with thickness from 0.5 m to 30 m, using PbO-B2O3 flux, on YAP substrates with
different orientations. For imaging application, the demand in terms of crystal optical
quality is high, therefore a big effort in terms of optimization of the growth conditions was
needed. We studied the morphology of the film by X-ray diffraction, scanning electron
microscopy and interferometric optical microscopy. A net improvement of the film quality
was observed with the reduction of the lattice mismatch between YAP substrate and film,
obtained introducing a fraction of Lu in the film composition. The segregation coefficient of
Gd and Lu was studied for films obtained with different melt composition and different growing
parameters. In order to obtains films that were suitable for imaging application, the films
were doped with a small amouth of rare-earth (Ce, Tb or Eu). Results about the
luminescence properties will also be shown in this presentation. Lastly, first X-ray imaging
test results using these kind of scintillators will be presented.
The authors acknowledge the support of E. Ziegler for the experiments at BM05 at ESRF.
A.G.P. and C.D. acknowledge the support of the Inter- national Associated Laboratory (CNRS–France & SCS–Armenia) IRMAS and of the European Union FP7/2007–
2013 under grant agreements 295025-IPERA. Y.Z. is supported by Polish NCN No 212/07/B/ST5/02376 grant agreement.
[1] A. Koch, C. Raven, P. Spanne, A. Snigirev, J. Opt. Soc. Am. A, 15-7 (1998) 1940-1951
[2] T. Martin, P-A. Douissard , M. Couchaud et al. IEEE trans. nuc. sci., 56-3 (2009)
[3] P-A. Douissard, T.Martin, F.Riva et al., IEEE trans. nuc. sci., 61-1 (2013) 433-438
Controlling Polymorphism in Organic Thin Films by Light
Linus Pithan1, Caterina Cocchi1,2, Christopher Weber1, Anton Zykov1, Sebastian Bommel1,3, Steven J. Leake4,
Peter Schäfer1, Claudia Draxl1,2, Stefan Kowarik1*
1
Institut für Physik, Humboldt-Universität zu Berlin, Newtonstrasse 15, 12489 Berlin (Germany)
IRIS Adlershof, Humboldt-Universität zu Berlin, Zum Großen Windkanal 6, 12489 Berlin (Germany)
3
Deutsches Elektronen-Synchrotron (DESY), Notkestrasse 85, 22607 Hamburg (Germany)
4
Swiss Light Source, Paul Scherrer Institut, 5232 Villigen PSI, Switzerland; present address: ESRF - The European
Synchrotron, 71 Avenue des Martyrs - CS 40220, 38043 Grenoble Cedex 9 (France)
2
Controlling crystallization is one of today’s challenges for high-performance organic electronic
devices. We demonstrate for the organic semiconductor alpha-sexithiophene (6T) that
polymorphism in molecular thin film growth can be manipulated with light. Vacuum deposited
films of 6T grown on potassium chloride (KCl) exhibit a bimodal growth with two co-existing
crystal phases, the low-temperature (LT) and the high-temperature (HT) 6T polymorphs [1]. We
find that laser illumination (λ=532 nm, 1.5 W/cm2) during growth suppresses the formation of HT
crystallites, thus the phase purity is enhanced compared to the growth without light (Figure 1a).
Through x-ray diffraction experiments (Figure 1b) we are able to determine a phase coexistence
ratio and find that illumination suppresses the formation of the HT phase by a factor of four. To
understand the mechanism behind this optical control, we use in situ x-ray diffraction, atomic force
microscopy (AFM), optical absorption measurements, as well as first-principles calculations for the
optical absorption spectra of the HT and LT phase. From these we deduce that the phase
purification is due to optical heating of the film and lower cohesive energy of the HT phase
compared to the LT phase. This method to increase phase purity is not limited to 6T molecules, but
we also present first results for a pentacene thin film demonstrating the applicability of light
directed growth for a wider range of molecular materials. Our findings show that light can serve as
an additional, not yet technologically used control parameter in molecular crystal growth to
optimize the structural quality of organic thin films.
Figure 1. a) Sketch of the experiment: Growth of HT-phase is suppressed in illuminated substrate regions.
b) XRD-scan highlighting the significant suppression of the HT crystal phase through illumination.
References:
[1] L. Pithan, C. Cocchi, H. Zschiesche, C. Weber, A. Zykov, S. Bommel, S. J. Leake, P. Schäfer, C. Draxl
and S. Kowarik, Cryst. Growth Des., 2015, 15 (3), pp 1319–1324
PDIF-CN2 organic thin-film deposited at room temperature by supersonic
molecular beam deposition for n-type OTFT
Chiarella Fabio1*, Barra Mario1, Chianese Federico1, Toccoli Tullio2, and Cassinese Antonio1
1
CNR-SPIN and Physics Department, University of Naples, Piazzale Tecchio 80, I-80125 Naples, Italy
2
IMEM-CNR-FBK Division of Trento, Via alla Cascata 56/C, I-38123 Povo, Italy
The possibility to get high-mobility n-type transistors avoiding thermal treatments during or
after the deposition could significantly extend the number of substrates suitable to the fabrication of
flexible high-performance complementary circuits. In this contribution, we report on the fabrication
of N,N’-1H,1H-perfluorobutildicyanoperylenediimide (PDIF-CN2) organic thin-film transistors
(OTFT) by Supersonic Molecular Beam Deposition (SuMBD) on silicon dioxide dielectric treated
with Hexamethyldisiloxane (HMDS) in the bottom contact-bottom gate configuration. The best
device exhibited mobility (µ) up to 0.2 cm2/Vs even if the substrate was kept at room temperature
during the organic film growth. This µ value exceeds by three orders of magnitude the electrical
performance of PDIF-CN2 films grown at the same substrate temperature by conventional Organic
Molecular Beam Deposition (OMBD). This achievement is possible thanks to the high kinetic
energy (Ek is at most 18 eV) reached by the molecules during SuMBD process, where Ek plays very
effectively the equivalent role of the substrate temperature in the OMBD technique [1]. By SuMBD,
however, the PDIF-CN2 film growth turns out to be very critical with respect to the deposition
parameters (in particular the deposition rate). In the figure 1, for example, it is possible to observe
the critical dependence of the measured charge carrier mobility on the deposition rate assumed
during the film growth. Moreover, it was observed that the reported final electrical response can be
obtained only waiting for some days after the deposition. Just after deposition, indeed, these OTFT
display very poor electrical performances. This effect is associated to a post deposition
crystallization and molecular reorganization effect monitored through Atomic Force Microscopy
and X-ray diffraction measurements.
Figure 1. Mobility extracted by OTFT trans-conductance in saturation regime for different devices obtained depositing
PDIF-CN2 film at different deposition rates by SuMBD. All dashed lines are guide for the eyes.
References:
[1] F. Chiarella, T. Toccoli, M. Barra, L. Aversa, F. Ciccullo, R. Tatti, R. Verucchi, S. Iannotta,
and A. Cassinese APPLIED PHYSICS LETTERS 104, 143302 (2014)
POSTER
S08-P01
Impact of boron on the step-free area formation during molecular beam epitaxial growth on MESA
structures on Si(111)
Ayan Roy Chaudhuri*, H.-Jörg Osten and Andreas Fissel
Institute of Electronic Materials and Devices, Leibniz University of Hannover, Germany
*[email protected]
Persistent downscaling of Si based semiconductor devices has reached to a level where the characteristic dimension of the devices
will soon be comparable to the surface roughness and atomic steps on the Si wafers. Atomic steps on Si wafers which can give rise
to thickness non-uniformity can drastically affect the device performance in this thickness regime. Further, electrical properties of
quantum effect based emerging devices (e.g. Resonant tunnel structures) are also anticipated to be compromised by such atomic
steps. In this regard presence of atomic steps and surface roughness of Si shall eventually become significant technological
challenge. Since step free Si wafers cannot be manufactured, the only way to overcome this problem is to create step free areas on
Si substrates. Recently, the preparation of step-free mesas on Si(111) with areas of 10m×10m by Si molecular beam epitaxy
(MBE) at 1120 K has been demonstrated.1,2 Utilisation of MBE growth to prepare step free Si MESA can have advantage over the
widely discussed sublimation process since this technique can limit the drawbacks (e.g. defect formation, dopant precipitation etc.)
associated with the later. However, the MBE grown Si layers on top of the mesas are non-doped, which restricts the applicability of
the atomically flat MESA-structures.
In this study, we investigated the influence of a typical Si-dopant (Boron) on the formation of step-free areas on the MESAstructures. For comparison, the Si-MBE growth experiments were performed under the same conditions (temperature, deposition
rate, deposition time) used in the earlier experiments without dopants.
Two different approaches were studied. In the first approach B and Si were co-evaporated during MBE process to achieve
in-situ doping. Boron co-deposition was found to drastically reduce the flat areas of only up to 1μm2. This indicates strong influence
of boron on the step-flow growth behavior. In this case boron acts as surfactant3, like antimony4 which hinders the step flow growth.
In the second approach boron was deposited at a lower temperature (~ 900K) prior to Si deposition which lead to the well
known √3x√3 reconstruction in RHEED. Here, we have also studied the influence of boron coverage (b) within a range of 0.3 to 1
ML. Subsequent Si was grown at 1130 K on top of the √3×√3-B surface. For all the samples the √3×√3 surface reconstruction
remained unchanged during and after the Si layer growth which indicates strong boron segregation under the present growth
conditions. Thereby, boron should occupy only subsurface sites of the grown layer and the surface should be nearly free of Si
dangling bonds at b ≥ 0.5 ML.5 In case of saturated B coverage, that means chemically passivated silicon substrate surface which
behaves like a surface in the van der Waals-epitaxy.6 Therefore, the growth behaviour could be different at b ≤ 0.5 ML and b ≥
0.5 ML.
Our experiments revelaed that growth of Si on B covered MESAs results in a gradual reduction of step-free area dimension
with an increase in the boron coverage. On growing ~60 nm epitaxial Si on different boron covered surface, the areas of step free
regions were found to reduce from 45 m2 for b ~ 0.3 ML, to 4.5 µm2 for 0.5 ML down to 1.5 µm2 for 1 ML. This could be explained
by the passivation of also step edges on Si(111) surface, which can no longer act as effective sinks for Si adatoms.7 In presence of B
sub-surfactant the step edge passivation can be expected considering that pre-deposited boron segregates towards the growth front
during the Si deposition. This results in a considerable increase in adatom density in front of the steps which reaches a critical value
required for nucleation of Si islands (critical supersaturation). However, during the Si layer growth, boron will be also incorporated
into the Si lattice up to the limit of solubility, what reduces the amount of boron available for surface dangling bond saturation.
Therefore, surfactant effect becomes smaller with the lower initial boron coverage as well as with an increase in Si layer thickness.
That is supported by observed increase in step-free area dimension (72 µm2) after the growth of 120 nm Si on Si MESA structures
covered with 0.3 ML boron.
Acknowledgement:
This work was supported financially by the Deutsche Forschungsgemeinschaft (DFG project FI 726-10)
References:
1 A. Fissel, J. Krügener, and H. J. Osten, Phys. Stat. Sol. C 9, 2050 (2012).
2 J. Krügener, H. Jörg Osten, and A. Fissel, Surf. Sci, 618, 27 (2013).
3 D. Kandel and E. Kaxiras, Phys. Rev. Lett. 75, 2742 (1995).
4 G.G. Jernigan and P.E. Thomson, Thin Sol. Films 380, 114 (2002)
5 A. Fissel, J. Krügener, D. Schwendt, and H.J Osten, Phys. Stat. Sol. A 207, 245-253 (2010).
6 J. Krügener, H.J. Osten, and A. Fissel, Phys. Rev. B 83, 205303 (2011).
7 A. Fissel, Ayan R. Chaudhuri, J. Krügener, H. Jörg Osten, J. Cryst. Growth (in press)
S08-P02
SEMIPOLAR AlN AND GaN ON Si(100):
CONCEPT, HVPE TECHNOLOGY AND LAYER PROPERTIES.
Bessolov1 V., Kalmykov1 A., Konenkova1 E.,
Kukushkin2 S., Myasoedov1 A., Red’kov2 A., Rodin1 S.
1A.F.Ioffe
institute, Politekhnicheskaya, 26, St.Petersburg, 194021, phone. +7(812)2927344, e-mail: [email protected];
2
Institute of problems of Mechanical Engineering, V.O., Bolshoj pr., 61, St.Petersburg, 199178
Introduction. The structures based on the semi-polar Gallium Nitride play an important role in production of light-emitting and laser diodes. Among
different materials such as Al2O3, SiC, and Si the most promising substrate for such optoelectronic structures is Silicon due to availability of large
size substrates (up to 300 mm), proper cost of manufacturing and acceptable values of thermal and electric conductivities.
Technology. The semipolar GaN layers on Silicon were synthesized by combination of two consequent techniques. At the first stage the layer of
SiC with the thickness of about 30 nm has been formed by solid phase epitaxy [1] on the Si(001) substrate misoriented in the (011) direction by 4–7
degrees. Then, at the second stage the buffer layer of AlN with the thickness from 300 nm up to 3 µm has been synthesized by HVPE method [2].
Thereafter the main GaN layer up to 15 µm thick has been grown.
The experimental results. The half widths of rocking curves (FWHM) measured on the semipolar GaN layers obtained had the value of
approximately 20–25 arcmin. Transmission electron microscopy (TEM) and Scaning Electron Microscopy (SEM) have shown that AlN and GaN
layers synthesized on the misoriented Si(001) substrate have the characteristic structure of semipolar AlN and GaN (Fig.1). TEM has shown that
the axis "a" of the GaN layer coincides with the Si[011] and 3C-SiC[011]directions, whereas the axis “c” is almost parallel to the Si<111> direction.
However, the angle φ from the Si(001) surface normal depends on the angle of the substrate misorientation χ as φ = 55o – χ. So, φ = 510 for the
semipolar GaN synthesized on the Si(001) substrate misoriented by χ=40 (Fig.2а) and φ = 480 for the misorientation χ=70 (Fig. 2b). A significant
deviation (about 1.5°) between AlN[0001] and GaN[0001] directions has been detected.
(а)
(b)
Fig.1. TEM and SEM images of the cleveage plane (a) and the surface (b) of AlN/SiC/p-Si(100) misoriented by 4°.
The main defects in a semipolar layer are basal plane staking fault and the partial dislocations bounding stacking faults (Fig.2). The relationship between the misorientation direction and the
displacement vectors of the defects has been found.
(a)
(b)
Fig. 2. TEM image of cross-sectional GaN/AlN/3C-SiC/Si(001) heterostructure with different surface misotientation to [110] direction (a) -4 degree, (b) – 7 degree. The arrows
indicate the stacking fault (SF) in GaN layers, which appears in [0001] direction. ILs – intermediate AlN and 3C-SiC layers.
The model.
Structural characteristics of semipolar GaN and AlN layers synthesized by HVPE, as well
as XRD data for 3C-SiC/Si(001) quasisubstrates synthesized by solid-phase epitaxy,
correspond to the model, which is based on preliminary implantation into the crystals
lattice of a silicon carbon atoms matrix from a carbon oxide (CO) source. In the initial
formation phase C atoms occupy interstitial positions in the silicon matrix.
Fig.3. Some GaN semi-polar planes, which lie between the m- and c-planes.
In the course of solid state epitaxy the activated complex transforms into silicon carbide. However, if the Si (100) plane tilted by 1-10°
from <100> axis towards <011> is heated to a temperature above 600оС, the formation of steps on it will be thermodynamically favorable.
It is known that the silicon lattice is most “loose” along the <011> directions, which is related to crystallographic structure of the Si
lattice. CO molecules drift along this direction inside silicon lattice perpendicular to steps. As a result of Si and CO interaction the
"silicon vacancy - carbon atom - silicon matrix" dipoles will be formed. Since the attraction between silicon vacancies and carbon atoms
in the silicon matrix is the strongest along <011> direction, some part of the (011) Si step transforms into (111)3C-SiC step with a slope
angle of ~55°. During the second stage, the semipolar AlN and GaN layers were synthesized on such 3C-SiC surfaces.
Conclusion. Thus, a new approach is proposed semipolar gallium nitride layers growth on planar Si(100) substrates. This approach is based on
the growth of 3C-SiC(111) layers on the misoriented Si(100) substrate by using the solid phase epitaxy and then the semipolar GaN and AlN layers
are synthesized by HVPE (Fig.3). The proposed approach to preparation of thick gallium nitride layers on silicon substrate can be applied for
formation of the ‘templates’ intended for fabrication of the structures for gallium nitride optoelectronics.
References.
[1]. S.A. Kukushkin, A.V. Osipov. J. Physics D: Appl. Phys. 47, (2014) 313001.
[2]. V.N. Bessolov, E.V. Konenkova, S.A. Kukushkin, A.V. Osipov, S.N. Rodin. Rev.Adv.Mater. Sci. 38 (2014) 75.
S08-P03
Structure of AlN layer obtained by thermochemical nitriding of (0001) sapphire
substrate with terrace-step surface
Vovk Olena*1, Nizhankovskyi Sergii1, Kryvonogov Sergiy1, Budnikov Olexander1, Muslimov Arsen2
1Institute
for Single Crystals, National Academy of Sciences of Ukraine, 60 Lenin ave., Kharkiv, 61001 Ukraine
2Shubnikov
Institute of Crystallography, Russian Academy of Sciences, 59, Leninskii pr., Moscow, 119333 Russia
For the mass production of technical devices based on nitrides of third-group metals (GaN, InN and AlN)
the great attention paid to use of modified sapphire substrates with a buffer nitride layer (GaN/sapphire or
AlN/sapphire), which play a role nitride quasisubstrates. Sapphire substrates with regular nanostructures on
the surface in the form of parallel terraces and steps have attractive interest for production of AlN/sapphire
templates. Availability predetermined regular nanosized structure allows to reduce the probability of chaotic
nucleation and nonuniform growth of the nitride layer caused mismatching parameter a of crystal lattice of
AlN and sapphire (13.4 %).
The initial surface of sapphire substrates (0001)±(5-15)' had terrace-step structure with step widths from
50 to 150 nm. The roughness Ra was measured to be 0.2-0.4 nm. AlN/sapphire templates was obtained by
thermochemical nitridation of sapphire in a mixture of nitrogen with the gaseous reductants СО and H2
(<1 vol.%) at 1450 оС by the technique described in detail in [1]. It was established that the nitride layer
repeats the terrace-step structure of the substrate surface. Thermochemical etching results in distortion of
sapphire substructure. It was found the degree of distortion of the step structure and roughness of the
sapphire substrate increase with increasing both the reducing potential of the medium and the annealing time.
Transmission electron microscopy of the template cross section (Fig.1) revealed the continuous
aluminium nitride AlN film of thickness about 100 nm with a clear boundary AlN/Al2O3 on the surface of the
sapphire substrate after thermochemical nitridation. Single-crystal phase AlN with hexagonal wurtzite structure
was determined by reflection high-energy electron diffraction . Indexing of the electron diffraction pattern
shows that AlN film is oriented by (0001) plane in parallel to the substrate surface and composed of blocks
with small misorientation angle relative to each other. On TEM images it's clearly seen that interblock
boundary begins from the edge of the step (Fig.1). The FWHM of the X-ray rocking curve of the nitride layer is
43 ang.min.
Figure 1. Cross-sectional TEM image of the sapphire substrate surface after the thermochemical nitridation.
References:
[1]. S.V. Nizhankovskiy, A.A. Krukhmalev, H.Sh. Kaltaev et al., Phys. of the Solid State, 54, 1896 (2012).
S08-P04
Growth of α-Cr2O3 thin films on α-Al2O3 substrate at low temperature by r.f. magnetron sputtering
Y. Gao, H. Leiste, M. Stueber, S. Ulrich
Karlsruhe Institute of Technology (KIT), Institute for Applied Materials (IAM-AWP), Hermann-von-Helmholtz-Platz 1, 76344 EggensteinLeopoldshafen, Germany
α-Cr2O3 thin films with a thickness of ~180 nm were grown on c-plane α-Al2O3 (0001) single crystal substrate
at low temperature of 320
by reactive radio frequency magnetron sputtering.
The phase formation and composition was characterized by X-ray diffraction (XRD), Raman spectroscopy and
Infrared spectroscopy (IR). In Bragg Brentano XRD patterns, the (0006) and (00012) reflections of
rhombohedral α-Cr2O3 were identified, and the full width at half maximum (FWHM) of (0006) and (00012)
Cr2O3 peaks are 0.3° and 0.8°, respectively. The rocking curve of (0006) reflex from films was performed to
determine the epitaxial quality of the film with respect to the substrate. Raman and IR results confirmed the αcorundum structured Cr2O3 phase grown on α-Al2O3 substrate. Further information such as in-plane and outof-plane lattice parameters, strain relaxation, defects, texture and orientations was obtained by reciprocal
space mappings (RSMs) and pole figure measurements. The symmetric (0006) and asymmetric (10 10)
RSMs from α-Cr2O3 thin films grown on α-Al2O3 substrate were measured. The reflection from (0006) α-Cr2O3
is not exactly equal to
, suggesting there is some tilt or misorientation of the α-Cr2O3 (0006) crystal
plane from the α-Al2O3 (0006) plane. From the RSM measurements, lattice constants a and c of film and
substrate are calculated. X-ray pole figure taken from the (0006) reflection of α-Cr2O3 films suggests the film
shows a fiber texture orthogonal to the surface of the samples but with a small level of tilt. In pole figures of
(10 10) reflections from the film and the substrate, six-fold symmetry reflections from α-Cr2O3 and three-fold
symmetry reflections from α-Al2O3 were observed, indicating that the α-Cr2O3 films have strong texture on αAl2O3 with rhombohedral structure and there are two different in-plane (10 10) orientations rotated by 60°
domain variants. It also suggests that stacking faults are caused during the film growth.
S08-P05
n-i-p triple junction obtained by the Atomic Layer Deposition method
Sylwia Gieraltowska1*, Lukasz Wachnicki1, Bartlomiej S. Witkowski1, Marek Godlewski1,2
1
Institute of Physics, Polish Acad. of Sciences, Al. Lotnikow 32/46, 02-668 Warsaw (Poland)
Cardinal S. Wyszynski University, Dept. of Mathematics and Natural Sciences College of Science, Dewajtis 5, 01-815
Warsaw (Poland)
2
An important feature of zinc oxide (ZnO) and gallium nitride (GaN) materials are their
similar physical properties such as a large band gap energy of about 3.4 eV and high crystalline
quality in the wurtzite structure. This opens the possibility to use them as materials for a n-p
junctions for applications in optoelectronics.
We investigated the influence of interlayer (intrinsic layer) between n-type ZnO and p-type
GaN on structural, electrical and optical properties of this heterostructure. Such junctions are
promising structures for light-emitting diodes (LEDs) and light detectors in the range of ultraviolet
radiation. This work concentrates on explanation of the influence of oxide interlayers in
optoelectronic structures, and on an optimization of growth parameters (in the atomic layer
deposition - ALD process) of all oxide layers. Composition of dielectric films (HfO2, TiO2, ZrO2
and Al2O3) is also optimized. The layers are used as intrinsic barriers in the n-i-p junctions. The
electrical, structural and optical properties of such electronic elements can be controlled by
modifying composition and growth parameters of selected oxide materials.
Our first investigations show that ZnO-based electronic structures can not only be more
sensitive, but much cheaper, as well, in comparison LEDs, laser diodes based on n-GaN/p-GaN
homojunctions. The intrinsic layer is able to improve the performance of the n-ZnO/p-GaN junction
LEDs and realize color shift when the driving current increases and the growth parameters change.
Discussion of important factors for possible manufacturing of these electronic devices will be
presented underlining simplicity and low costs of our approach, as well as use of environmental
friendly and low power technology.
This work was partially supported by the National Science Centre (decision No. DEC2013/09/N/ST5/00901).
S08-P06
2D-islands Nucleation on Si(111) at High Temperature During Sublimation and
Thermal Etching by O2
Sergey Sitnikov*, Sergey Kosolobov, Alexander Latyshev
Rzhanov Institute of Semiconductor Physics
Siberian Branch of Russian Academy of Sciences, pr. Lavrentieva 13, Novosibirsk, Russia, 630090 (Russia)
The problem of mass transport in surface physics is of interest topic of research due to high
importance for theoretical and technological applications. Atomic mechanisms of the surface
diffusion play essential role in the processes of low-dimensional systems and nanoscale objects
formation during MBE, gas reactions and sublimation. However, there is lack of information on the
characterization of the atomic processes and diffusion parameters on the silicon surface at high
temperatures; this may be due to technical difficulties in detecting of high-speed surface processes.
We have used in situ ultrahigh vacuum reflection electron microscopy to investigate the process
of two dimensional negative islands (etching pits) nucleation on extremely wide (up to 120μm in
diameter) terraces at Si(111) surface during sublimation and thermal etching with molecular oxygen
at temperatures above 1000 °C. We used classical theoretical model of nucleation [1] applied to
vacancy coagulation on circular terrace, bounded by closed atomic step. By analyzing nucleation
kinetics at different temperatures and comparing the results with theoretical model, we determined
the dominant surface mass transport mechanism. The squared critical terrace size Dcrit2 for
nucleation of new island is found to follow power law form with scaling exponent χ changing from
0.95 to 1.15 as the temperature increased Tcrit= 1180°C. At temperatures above Tcrit we found the
increasing of the critical terrace size at temperatures above Tcrit during sublimation and thermal
etching by oxygen (figure 1). These findings are in agreement with previously reported step-like
increasing in step spacing on Si(111) during sublimation [2]. By analyzing the kinetic of the atomic
steps motion during sublimation and oxygen etching we have estimated the energy of the vacancy–
step interaction EAD as 1.5±0.15 eV and the activation energy of the bulk-surface vacancy exchange
process as 4,2 ±0,1 eV. We conclude that observed changes of the Dcrit in high temperature region
(above Tcrit) can occur through detachment–attachment kinetics of vacancy–step exchange process
rather than via surface diffusion. This work was partly supported by the Russian Foundation for
Basic Researches (grant 14-08-31552) and all experiments were carried out on the equipment and
under supporting of CKP “NANOSTRUKTURY”.
Figure 1. Temperature dependence of critical diameter terrace at sublimation and different rate of thermal etching with
molecular oxygen.
References:
[1] I.V. Markov, Acta Crystallogr. A 60 (2004) 355,
[2] Y. Homma, H. Hibino, T. Ogino, N. Aizawa, Phys. Rev. B 55 (1997) R10237
S08-P07
β -Ga2O3 crystal deposition on sapphire and silicon substrates by chemical
assisted vapor transport method
Pechnikov Aleksey1,3 Nikolaev Vladimir1,2,3, Maslov Viktor1,2*, Krymov Vladimir 1,2, Stepanov Sergey 1,4
Bougrov Vladislav1, Romanov Aleksey1,2,
1
ITMO University, Kronverkskiypr, 49, 197101, St-Petersburg, (Russia)
Ioffe Physical Technical Institute, RAS, Polytechnicheskaya st., 26, 194021, St. Petersburg, (Russia)
3
Perfect Crystals LLC, Polytechnicheskaya st., 28, 194064, St. Petersburg, Russia
4
Peter The Great Saint Petersburg Polytechnic University, Polytechnicheskaya st., 29, 195251, St. Petersburg, Russia
2
Gallium (III) oxide crystals (β-Ga2O3) are currently considered as one of the most promising
wide band-gap semiconductors (Eg ~ 4.9 eV). Specific advantages of this material are the
transparency to the UV-C range and high breakdown voltage; at the same time, appreciable
conductivity can be achieved by doping. This makes β-Ga2O3 an alternative to indium and tin
oxides for transparent conductive contacts. A high-voltage transistor prototype based on gallium
oxide was already demonstrated [1], an experimental batch of energy-efficient light-emitting diodes
was produced [2].
Gallium oxide deposition from gallium oxide powder on silicon substrate and sapphire substrates
has been studied. Gallium oxide powder is thermally evaporated from the crucible to the surface of
the substrate at various temperatures (10000C-18000C) under argon. It has been found that the
morphology of the films mainly depends on the substrate temperature, the deposition rate and the
rate of re-oxidation. The crystallographic quality of the layers has been obtained at high
temperatures for sapphire substrates. It strongly depends on orientation of sapphire substrate [3].
References:
[1] E. G. Villora, Kiyoshi Shimamura, Yukio Yoshikawa, Takekazu Ujiie, and Kazuo Aoki, Appl. Phys.
Lett. 92 (20), 202120 (2008).
[2] H. Aida, K. Nishiguchi, H. Takeda, N. Aota, K. Sunakawa, and Y. Yaguchi, J. Appl. Phys. 47 (11), 8506
(2008).
[3] V.N. Maslov, V.I. Nikolaev, V.M. Krymov, V.E. Bugrov, A.E. Romanov, Physics of the Solid State,
2015, Vol. 57, No. 7, pp. 1342–1346.
S08-P08
Dependence of the relaxation of elastic stress on the sign of strain in SiGe
epitaxial layers
Novikov Alexey*1, Yurasov Dmitriy1, Shaleev Mikhail1, Yunin Pavel1
1
Institute for Physics of Microstructures RAS, 603950, GSP–105 Nizhny Novgorod (Russia)
One of the advantages of transfer from growth on Si(001) substrate to growth on relaxed SiGe
buffer is the ability of formation of the layers with the different signs of strain in one structure
which significantly expands the opportunities for fabrication of silicon-based devices. The deep
insight of the processes of elastic stress relaxation is needed for fabrication of the SiGe
heterostructures with desired parameters. However, to date the processes of plastic (via defect
formation) and elastic (via development of surface roughness) relaxation of stress in SiGe layers
(especially for tensile-strained layers) grown on relaxed buffers are studied much less as compared
with compressed SiGe layers grown on Si(001) substrates.
In the present paper the features of strain relaxation in different types of SiGe heterostructures
grown by MBE on relaxed SiGe buffers were studied. Special attention was paid to investigation of
the relaxation of elastic stresses in tensile GeSi layers grown on Ge(001) substrates. Usage of
substrates with different lattice constants helped to reveal the influence of type of elastic strain on
the SiGe growth process. It was obtained that at the same lattice mismatch between the deposited
film and the substrate the thickness at which the onset of stress relaxation via development of the
surface roughness occurs (critical thickness of 2D growth) is significantly higher for tensile GeSi
layer than for the compressive strained layers. This effect is related with the different influence of
tensile and compressive strain on the development of surface roughness on Si and Ge (2x1)
reconstructed (001) surfaces [1]. Indeed according to AFM and RHEED data deposition of the
tensile GeSi layers on SiGe buffer or Ge(001) substrates results in the smoothing of the surface. At
the same time, the deposition of compressed SiGe layers on Si (001) substrate or on the SiGe buffer
causes the development of surface roughness already at the early stages of growth, which
subsequently leads to nanoislands formation. It was obtained that the critical thickness of 2D
growth of tensile-strained GeSi layers on Ge(001) substrate is higher than the critical thickness of
their pseudomorphic growth (critical thickness at which the plastic relaxation occurs). As a result,
growth of the coherent self-assembled quantum dots cannot be achieved in the case of
GeSi/Ge(001) tensile-strained structures.
It was demonstrated that the ability of formation of layers with the different signs of strain in
the case of growth on relaxed SiGe buffer gives the additional opportunities to control the growth of
strained SiGe heterostructures [2]. In particular, the predeposition of a thin tensile strained layers
significantly increase the critical thickness of 2D growth of compressed SiGe layers on relaxed
buffer [2].
The work was supported by RFBR (grants # 13-02-01006-а, 14-02-01116-а and 13-0212108-ofi_m) and the Scholarship of President of Russian Federation for young scientists SP5485.2013.5.
References:
[1] Xie Y.H., Gilmer G.H., Roland C., Silverman P.J., Buratto S.K., Cheng J.Y., Fitzgerald E.A., Kortan
A.R., Schuppler S., Marcus M.A., Citrinet P. H. al., Phys. Rev. Lett. 73 (1994)
[2] Shaleev M.V., Novikov A.V., Yurasov D.V., Hartmann J.M., Kuznetsov O.A., Lobanov D.N., Krasilnik
Z.F., Appl. Phys. Lett. 101 (2012) 151601
S08-P10
Influence of thermal treatment on the optical and electrical properties
of ZnO:B thin films
Kh.A. Abdullin1, L.V. Gritsenko1,2*, N.R. Guseinov1, D.V. Ismailov1, Zh.K. Kalkozova1,
S.E. Kumekov2, Zh.O. Mukash2, E.I.Terukov3
1Kazakh
2Kazakh
3Ioffe
National University after al_Farabi, al_Farabiave. 71, Almaty, Kazakhstan
National Technical University after K.I. Satpaev, Satpaev str., 22, Almaty, Kazakhstan
Physico-Technical Institute, 26 Politekhnicheskaya, St Petersburg, Russian Federation
*[email protected]
Zinc oxide (ZnO) has unique properties, such as wide band gap ~ 3.37eV, a large exciton binding energy
(~ 60 meV), and effective ultraviolet photoluminescence, what makes it attractive for practical applications.
Currently ZnO is one of the most actively studied wide-band semiconductor materials. Zinc oxide is promising
to create a new generation of bright optoelectronic devices such as light-emitting diodes, based on
heterostructures and homostructures, due to a large exciton binding energy.
Today, the zinc oxide is used in the short-wavelength LEDs [1], detectors, piezoelectric devices [2],
sensors [3], power electronics, in dye solar cells, and in many other applications. In particular, boron doped
ZnO thin films, are used as the transparent and conductive front contact of solar cells.
The temperature of samples increases during the treatment and exploitation. It leads to the changes of
ZnO films properties and can adversely affect on the devices performance. Therefore, the study of the
electrical and optical properties modification exposed to the heat treatment is an important task for application
of thin films in optoelectronics and solar cells.
Experimental results on optical and electrical properties of ZnO:B thin films deposited by MOCVD on the
glass substrates are presented in the report. The effect of thermal treatment in air and in vacuum on a change
of optical properties (absorption and transmission spectra, Raman scattering, photoluminescence − PL) and
electrical properties (concentration and carrier mobility, as well as the resistivity) of ZnO:B samples was
studied.
It was found that the optical absorption near band gap increases with increasing annealing temperature of
the samples. Excitonic PL band intensity increases under annealing approximately in three times. Annealing
of ZnO:B samples at temperatures above 200°C leads to the degradation of electrical properties: carrier
concentration as well as mobility decrease, while the resistivity increases. Subsequent annealing of samples in
vacuum at 450-500°C causes significant recovery of electrical parameters.
References:
[1] Zhong Lin Wang, Mater Today, 7 (2004) 26.
[2] De Sousa V. C., Morelli M. R., Kiminami G. A., Castro M. S., Journal of materials science: Materials in
electronics, 13 (2002) 319.
[3] S. K. Gupta, Aditee Joshi and Manmeet Kaur, J. Chem. Sci., 10 (2010) 57.
S08-P11
Preparation and optimization of a molybdenum electrode for CIGS solar cell
Feng Jingxue2, Zhuang Lin*1, Wang Xin2, Hong Ruijiang1, Shen Hui1
1.
School of Physics and Engineering, Institute for Solar Energy Systems, State Key Laboratory of Optoelectronic
Materials and Technologies, Guangdong Provincial Key Laboratory of Photovoltaics Technologies, Sun Yat-Sen
University, Guangzhou 510275, P. R. China
2.
School of Materials Science and Engineering, South China University of Technology, Guangzhou 510275, P. R.
China
Referring author: Sun Yat-Sen University, Zhuang Lin E-mail address: [email protected]
Single molybdenum(Mo) films were deposited by radio frequency (RF) and direct current (DC)
magnetron, respectively. With changing the deposition parameters including deposition pressure,
power and substrate temperature, the films show different surface morphology and crystallinity. A
lower resistivity and better crystallinity are obtained in the DC mode. It is shown that both the
crystallinity and grain size increase when the deposition pressure decreases. The crystallinity has no
significant changes when the deposition power varies from 100 to 200 W. With the substrate
temperature increases, the porosity and grain size of the Mo films increase. After the films were
annealed in furnace with inert Ar gas, the Mo films show denser structure and lower hole content.
The cross-sectional view of the Mo films has a columnar morphology, which indicates the films
have high crystallinity. The XRD result indicates that the crystallinity of the films has a strong
preferential orientation along the (110) plane in DC mode, which is shown in Fig.2. The lowest
resistivity of the single Mo film is 34×10-6 Ω·cm when the deposition pressure is 0.1Pa and the
deposition power is 300 W in DC mode. In order to obtain lower resistivity and better adhesion, a
three-layer film is deposited in DC and DC/RF mixed mode. The three-layer film shows good
adhesion and a low resistivity of about 50×10-6 Ω·cm, which is appropriate for CIGS solar cell.
Fig1
Fig2
Fig1. The cross-sectional view of the single Mo films
Fig2. Typical XRD spectra of DC and RF magnetron sputtered molybdenum thin films at 0.6Pa
S08-P12
Surface induced weak orientational order and role of isotropic nematicinterface fluctuations in the appearance of an induced nematic film
Elena S. Pikina1,2,* , Charles Rosenblatt3
111
2
Oil and Gas Research Institute, Russian Academy of Sciences, 119333 Moscow, Russia
Landau Institute for Theoretical Physics of the RAS, 142432 Chernogolovka, Russia
3
Department of Physics, Case Western Reserve University, Cleveland, Ohio, USA
Recently the nontrivial spatial and temperature dependence of the surface-induced weak planar orientational order
parameter Q(z,T) was determined experimentally just above isotropic-nematic (IN) phase transition point [1]. The
experiment was performed by immersing a highly tapered optical fiber into a thin liquid crystal layer and measuring the
optical retardation between the aperture and substrate as a function of height. The most intriguing features of these
results are that Q is considerably smaller than the bulk order parameter discontinuity QIN at the IN phase transition and
at all reduced temperatures t=(T-TIN)/(TIN-T*) Q(z) does not decay exponentially, but instead exhibits a “shoulder”
extending to about 30 nm from the substrate before decaying rapidly in space over an IN-interfacial coherence length of
order 5-7 nm. Here we present a theoretical explanation of the observed behaviour.
We obtain expressions for the short-range and long-range contributions to the interface potential of the induced nematic
film and demonstrate the repulsive interaction between the soft IN-interface and the bounding substrate. We propose a
method to determine the nematic order parameter profile in the induced nematic film using the numerical shooting
method. Thereafter the bare short-range repulsive interaction in these films is calculated by introducing a model nematic
order parameter profile. The bare nematic director thermal fluctuation-induced long-range repulsive interaction between
the weak IN-interface and bounding surface - the so called “pseudo-Casimir interaction” - is obtained using a functional
integral approach. It is shown that the small value of the IN-interfacial tension results in the renormalization of the
repulsive interaction potential due to the thermal fluctuations of the soft IN-interface. This leads to an increase of the
equilibrium thickness of the induced nematic film and
appearance of a step-like orientational order
parameter profile. We find that only renormalized
short-range and thermal pseudo-Casimir interactions
are essential for the appearance of the induced
nematic film, which provide the observed thickness
about 30 nm. The long-range van der Waals
interaction is shown to be negligibly small and the
dominant role is played by the renormalized shortrange repulsion. As a result, the experimental
dependences of the nematic order parameter
amplitudes [1] can be fitted with good accuracy, Fig.1.
The fitting makes it possible to determine the material
parameters of the system, including the amplitudes of
the surface interaction, the IN-interfacial tension and
the interfacial coherence length.
Reference:
[1] E. Pikina, C. Rosenblatt, Eur. Phys. J. E , 35, 87 (2012).
[2] J.-H. Lee, T.J. Atherton, V. Barna, A. De Luca, E. Bruno, R.G. Petschek, and C. Rosenblatt,
Phys. Rev. Lett. 102, 167801 (2009).
_____________________________________________
* presenting author; E-mail: [email protected]
S08-P13
Effects of thermal annealing on AlInGaN/AlN/GaN heterostructure grown by
MOCVD
R. Loganathan*1, P. Dhivya Maria Pushpam1 R. Ramesh and K. Baskar1
1
Crystal Growth Centre, Anna University, Chennai-25 (India)
Group III nitrides such as GaN, AlN and InN are wide bandgap semiconductors that have
attracted great interest in optoelectronics, high power and high frequency device applications due to
their high thermal stability, high carrier mobility and direct bandgap. Usually nitride based devices
are grown heteroepitaxially on a number of foreign substrates. Difference in the lattice parameter
and thermal expansion coefficient between the substrate and the epilayer cause poor crystalline
quality by introducing defects and cracks into the material. For a high quality device performance, a
material with good crystalline nature is required. Since thermal annealing is used as a processing
step in the fabrication of nitride based devices, it is used as a technique to improve the quality of
lattice mismatched layers [1][2].
In this study, nearly lattice matched AlInGaN/GaN heterostructure have been grown epitaxially
by Metal Organic Chemical Vapor Deposition (MOCVD) on Sapphire substrate with varying
indium composition from 3% to 5% with constant flow rates of TMGa and TMAl [2]. The as grown
samples were annealed in a tubular furnace ranging from 850°C to 950°C in steps of 50°C for 20-50
min in nitrogen ambiance. The samples were characterized before and after annealing process, the
morphological changes were studied with Atomic Force Microscopy (AFM) to find the root mean
square (RMS) roughness. The crystalline quality and composition were determined by HRXRD.
The composition of as grown AlInGaN has been estimated from omega/2theta scan and simulation
fit [Fig.1]. Reciprocal Space Mapping (RSM) was used to study the strain and relaxation between
the AlInGaN/GaN heterostructure. The optical properties have been investigated by
photoluminescence. The results have been discussed in detail.
Figure 1. Omega/2theta scan of AlInGaN/GaN heterostructure
References:
[1] R. Loganathan, M. Balaji, K. Prabakaran, R. Ramesh, M. Jayasakthi, P. Arivazhagan, Shubra Singh and
K. Baskar., Journal of Material Science: Materials in Electronics, (2015) DOI 10.1007/s10854-015-3082-4.
[2] J.P. Ahl, J. Hertkorn, H. Koch, B. Galler, B. Michel, M. Binder, B. Hollander. J. Cryst. Growth, Vol. 398
(2014) pp. 33-39.
S08-P16
Growth and Optical Investigation on InGaN/GaN Quantum well Structures
grown by Metal Organic Chemical Vapour Deposition
Kandasamy Prabakaran*1, Raju Ramesh1, Eric Faulques2, Krishnan Baskar1
1
Crystal Growth Centre, Anna University, Chennai, Tamilnadu (India)
Institute of Materials Jean Rouxel, University of Nantes, Nantes (France)
2
The InGaN/GaN Quantum Well structures were grown on c-plane sapphire substrate using
metal-organic chemical vapor deposition (MOCVD). Crystalline quality has been investigated using
High-resolution x-ray diffraction analysis and total dislocation densities of screw and edge types in
the GaN epilayer have been calculated [1]. The thickness and indium composition of the InGaN was
determined by HRXRD. From simulation fit, the composition of indium was found to be 10-15%
and thickness was around 5 nm and 10 nm . Surface properties of the samples have been analyzed
using Atomic force microscopy (AFM) and Scanning Electron Microscopy (SEM) respectively.
Energy Dispersive X-ray analysis (EDX) technique was applied to study the distribution of Indium
composition in the InGaN/GaN Quantum Well Structures. Room-temperature time-resolved
photoluminescence, photoluminescence (Figure. 1(a-c)) and Raman spectroscopy measurements
have been performed on InGaN/GaN Quantum Well Structures. The photoluminescence intensity
was degrades with increases of InGaN thickness and the results were discussed in detail.
Figure.1. Time Resolved Photoluminescence and Photoluminescence Spectra of InGaN with different
thickness and composition
References:
1. Kim, H. J., Liu, J., Zhao, Z. M., & Xie, Y. H, Journal of Vacuum Science & Technology B, 22(4)
(2004) 2257-2260.
S08-P17
Synthesis and thin films growth of BaBiO3, Ba1-xKxBiO3 and BaBiO1-yFz
compounds by pulsed laser deposition
Gawryluk Dariusz Jakub*1, Ristic Zoran1,2, Shi Ming1, Radovic Milan1, Plumb Nicholas1, Shiroka Toni3,
Mesot Joël1,3, Medarde Marisa1, Pomjakushina Ekaterina1, Conder Kazimierz1
1
Paul Scherrer Institut, CH-5232 Villigen PSI (Switzerland)
Institute of Condensed Matter Physics, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne (Switzerland)
3
Laboratory for Solid State Physics, ETH Zürich, CH-8093 Zürich (Switzerland)
2
Barium bismuthate - BaBiO3 (BBO) was identified as a charge-ordered insulator or Peierls
semiconductor [1] with a charge Bi3+/Bi5+ disproportionation [2] and a charge density wave
ordering (CDW) [3]. However, hole-doped Ba1-xKxBiO3 (BKBO) with ~ 0.37 ≤ x < ~ 0.5 is known
as a metallic compound showing superconductivity at ~ 30 K [4].
Very recently, it was theoretically predicted that the parent compound BBO, potassium doped
BKBO and also electron-doped BaBiO1-yFz (BBOF) are possible topological insulators with a large
energy gap [5] or even 2D superconductors [6].
We decided to study all these intriguing properties on heteroepitaxial films growth by the
Pulsed Laser Deposition (PLD). For these studies BBO, BKBO and BBOF targets have been
prepared. Chemical compositions of the targets were measured by the X-Ray Fluorescence (XRF)
and oxygen stoichiometry by the Termogravimetric Analysis (TGA). Crystallographic purity was
checked by the X-Ray Diffraction (XRD). Rietveld analyses of the obtained XRD patterns were
performed. Magnetic properties of the samples were studied using Superconducting Quantum
Interference Device (SQUID) magnetometer and Physical Property Measurement System (PPMS).
Films of BBO and BKBO were deposited on (100) MgO substrates. Structural and surface
quality of the films was in-situ monitored using Reflection High Energy Electron Diffraction
(RHEED). Structural (XRD), electrical (PPMS) and magnetic (SQUID) measurements were
performed on the series of the obtained films.
Figure 1. RHEED pattern from of the BBO thin film grown on MgO
References:
[1] Sleight A. W., et al., Solid State Commun., 17 (1975) 27. Tajima S. et al., Phys. Rev. B, 32 (1985) 6302.
Lobo R. P. S. M. et al, Phys. Rev. B, 52 (1995) 13294. Franchini C. et al, Phys. Rev. B, 81 (2010) 085213.
[2] Cox D. E. et al., Solid State Commun., 19 (1976) 969. Harrison W. A., Phys. Rev. B, 74 (2006) 245128.
[3] Wei X. et al., Solid State Commun., 81 (1992) 419. Kim H.-T., Phys. Rev. B, 54 (1996) 90. Hase I. et al.,
JPCS, 108 (2008) 1.
[4] Cava R. J. et al., Nature, 332 (1988) 814. Hinks D. G. et al., Nature, 333 (1988) 869.
[5] Jin H. et al., Sci. Rep., 3 (2013) 1. Yan B. et al., Nature Phys., 9 (2013) 709. Li G. et al., Scientific
Reports, 5 (2015) 10435.
[6] Vildosola V. et al., Phys. Rev. Lett., 110 (2013) 206805. [16] A. Taraphder et al., Europhys. Lett. 21, 79
(1993).
S08-P18
Properties of Crystalline Silicon Layers for Photovoltaic Application grown on
Glass by Steady-State Solution Growth
Christian Ehlers*, Roman Bansen, Jan Schmidtbauer, Franziska Ringleb,
Thomas Teubner, and Torsten Boeck,
Leibniz-Institut für Kristallzüchtung, Max Born-Str. 2, 12489 Berlin (Germany)
Silicon thin film solar cells require only several ten micrometers of crystalline silicon to absorb
sunlight efficiently. We developed a two-step process for depositing silicon on low cost glass
substrates to meet those demands.
Initially a seed layer of silicon is deposited on heated glass substrates by two different
approaches. Either only a thick amorphous silicon layer is deposited by physical vapor deposition,
or a metal such as tin is evaporated afterwards which results in the metal-induced recrystallization
of a thin amorphous silicon layer. In the second step, a silicon layer is grown epitaxially on the seed
layer by steady-state solution growth from a tin solution keeping the temperature below the
softening point of glass.
Unlike common liquid phase epitaxy where the growth process is driven by uniform cooling
and subsequent supersaturation of the metallic solvent, here a permanent temperature gradient
between the silicon source material and the glass substrate floating on the solution is employed.
Therefore, our process has substantial similarity to a conventional float glass production-process
which would allow for the deposition of silicon on glass in a continuous way.
We will present electrical and structural properties of the grown silicon layers and discuss their
suitability for solar cell devices.
S08-P19
CdHgTe deposited on CdZnTe substrates by Closed Space Sublimation
technique
S. Rubio, E. Repiso, A. Corrochano, M. Sochynskyi, J L. Plaza, E. Diéguez
Laboratorio de Crecimiento de Cristales, Universidad Autónoma de Madrid, Madrid, (Spain)
CdHgTe (CMT) is semiconductor material of great significance for the development of IR
detectors due to the fact that this material covers the IR range [1]. CMT epitaxial layers were
deposited on CdZnTe (CZT) substrates for the development of these devices. The use of CZT
crystals as substrates is due to lattice matched of CMT with CZT [2]. Usually, CMT layers are
growth by different deposition techniques such as Liquid-Phase Epitaxy (LPE) and Molecular Beam
Epitaxy (MBE) [3], [4].
In this work, CZT crystals has been studied in order to be employed as substrates in CMT/CZT
devices, later epitaxial layers of CMT have been deposited on CZT substrates by Closed Space
Sublimation (CSS) method, this deposition technique allows to develop layers at lower temperature
that the CdHgTe melting point and not required the use of ultra-high vacuum (UHV).
CMT and CZT crystals were employed as source and substrate material respectively. CZT
crystals were sliced and mechanically polished using different Al2O3 grain size. Before performing
the CMT deposition, CZT substrates were subjected to a chemical cleaning. The CMT layers were
deposited by Closed Space Sublimation technique about 500ºC for an average of 5 min being the
distance from the source to substrate between 1 - 3 mm and the chamber pressure base was 1 mbar.
Different characterizations in the CZT substrates and CMT/CZT samples were carried out in
order to study the crystal structure, chemical composition, IR transmittance and morphology by XRay Diffraction (XRD), Energy Dispersive X-Ray Spectroscopy (EDX), Inductively Coupled
Plasma Mass Spectrometry (ICP-MS), Total reflection X-Ray Fluorescence (TXRF), Fourier
Transform InfraRed spectroscopy (FTIR) and Scanning Electron Microscope (SEM). The chemicals
analyses carried out in the CZT substrates show a concentration of Zn close to 4%. Furthermore, the
XRD and FTIR spectrums indicate that main orientation is (111) and the transmittance is higher
than 55% in the infrared range. The CMT layers deposited on CZT present good homogeneity being
their chemical composition 49.9at%, 49.4at% and 0.7at% for Cd, Te and Hg respectively.
Figure 1. X-Ray Diffraction (XRD) spectra of CZT substrate
References:
[1]Tonheim, C. R., Sudbo, A. S., Selvig, E., & Haakenaasen, R. ,IEEE Photonics Technology Letters, 23,
(2011). 36-38.
[2] Skauli, T., Colin, T., Sjølie, R., & Løvold, S., Journal of Electronic Materials, 29 (2000) 687-690.
[3] Gravrand, O., & Destefanis, G., Infrared Physics & Technology, 59 (2013) 163-171.
[4]Belogorokhov, A. I., Smirnova, N. A., Denisov, I. A., Belogorokhova, L. I., & Levonovich, B. N. Physica
status solidi , 7, (2010) 1624-1626.
S08-P22
Growth and luminescent properties of single crystalline films of Ce3+
doped Gd1-xLuxAlO3 and Pr1-xLuxAlO3 perovskites
Yu. Zorenko1,2, T. Zorenko1,2, V. Gorbenko1,2, T. Voznyak2, A. Fedorov3, A. Suchocki4, Ya. Zhydachevski4
2
2
Institute of Physics, Kazimierz Wielki University in Bydgoszcz, 2 Powstańców Wielkopolskich str., 85090 Bydgoszcz (Poland)
Electronics Department, Ivan Franko National University of Lviv, 5 Dragomanova str.,79017 Lviv, Ukraine
5Institute
3Institute
for Single Crystal NAS of Ukraine, 60 Lenin av., 61178 Kharkiv (Ukraine) of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw (Poland)
The liquid phase epitaxy (LPE) technology offers the possibility of obtaining the high–density
single crystalline film (SCF) scintillators based on different oxide compounds [1, 2]. Namely, SCF
screens play a key role in 2D/3D detectors used for imaging applications at X-rays synchrotrons [2].
RAlO3 perovskites (Lu, Gd, Pr and their combination) are good candidates for high-efficient SCF
screens due to their high densities and effective atomic number [3]. Apart from that, the absorption Kedge of these compounds is located in an energy range where imaging applications is possible as well.
The results of composition engineering and luminescent properties of Ce3+ doped Pr1-xLuxAlO3
(PrLuAP) and GdxLu1−xAlO3 (GdLuAP) SCF have been presented in this work. We have used the
following research concepts: (i) “Ce3+ ion energy level positioning” [4]; (ii) “band gap engineering”
[5] and (iii) “enhancing the energy transfer from the host to Ce3+ ion”, which are applied to YAlO3:Ce
(YAP:Ce) scintillation material by the introduce of Gd3+ and Pr3+ ions into the cub-octahedral sites of
perovskite host in the concentration ranges x=0÷1.0 and x=0÷1.5, respectively.
Firstly, we search for the conditions of LPE growth of the SCFs of GdLuAP and PrLuAP
perovskites on cheap YAlO3 (YAG) substrate using the PbO-B2O3 based flux and found that the
full set of GdxLu1−xAlO3 SCFs with x values in x=0÷1.0 range and sets of PrxLu1−xAlO3 SCFs with
x values in x=0÷0.5 range can be successfully crystallized onto the same YAP substrates.
The luminescent properties of Ce3+ doped GdLuAP and PrLuAP SCFs were studied by traditional
spectroscopic methods, such as absorption, cathodoluminescence, light yield measurements under αparticles excitation and photoluminescence under excitation in the Ce3+, Pr3+ and Gd3+ related bands.
Namely, we have demonstrated the efficient Gd3+→Ce3+ energy transfer in GdLuAP SCF and the
efficient Pr→Ce energy transfer in PrLuAP SCF. The efficiency of the energy transfer in GdLuAP and
PrLuAP SCF with different Gd and Pr content strongly depends on the energy matching of 6Pj level of
Gd3+ cations or 5d1 levels of Pr3+ cations with 5d1 one of Ce3+ ions. For studying the Pr-Ce energy
transfer in perovskite host we have also performed the luminescent spectroscopy of Pr-Ce doped YAP
sample under excitation by synchrotron radiation at the Superlumi station at HASYLAB, DESY.
We have also found the significantly larger influence of Pb2+ flux related impurity on the LY of
3+
Ce emission in GdLuAP and PrLuAP SCF, in comparison with the YAP:Ce SCF, grown onto YAP
substrates. This effect is caused by the larger lead contamination in SCF of Gd-Pr based perovskites,
in comparison with the YAP counterpart due to the relatively larger dimension of the sites of
perovskite hosts, where the Pb2+ ions are localized. Thus, it is desirable to use the lead-free fluxes for
producing the SCF scintillators based on the multicomponent perovskites to achieve their higher LY.
References:
[1] Yu. Zorenko, V. Gorbenko, T. Martin, P.‐A. Douissard, , et all, Radiation Measurements 56 (2013) 415.
[2] Т. Мartin, A. Koch, Journal of Synchrotron Radiation, 13 (2006) 180.
[3] P.‐A. Douissard, T. Martin, F. Riva, Y. Zorenko, et all, Proc. SCINT2015 conference, San‐Francisco, 2015. [4] K. Kamada, T. Endo, K. Tsutumi, J. Pejchal, M. Nikl, K. Tsutumi, et all, Cryst. Growth Des., 11 (2011) 4484.
[5] Fasoli, M., Vedda, A., Nikl, et al., Phys. Rev., B 84, 081102(R) (2011).
This work was realized within the Polish NCN No 2012/07/B/ST5/02376 and Ukrainian SL-20F projects.
S08-P25
Strained Ge layers on virtual Si1-xGex(001) substrates
J. Schmidt*1, D. Tetzlaff1, E. Bugiel1 and T.F. Wietler1,2
1
Institute of Electronic Materials and Devices, Leibniz Universität Hannover,
Schneiderberg 32, D-30167 Hannover, Germany
2
Laboratory of Nano and Quantum Engineering, Leibniz Universität Hannover,
Schneiderberg 39, D-30167 Hannover, Germany
Strained Ge layers have become very interesting for their use in high mobility channels for
modern metal oxide semiconductor field-effect transistors (MOSFETs) [1]. Due to the large lattice
mismatch between Ge and Si (~ 4.2%), the use of a virtual substrate (VS) is required in order to
grow pseudomorphically strained Ge layers of higher thickness. In contrast to conventional methods
like graded buffers, the use of surfactant-mediated epitaxy (SME) using Sb as a surfactant provides
smooth, fully relaxed virtual substrates with a thickness of 500 nm [2].
Based on an adapted model for the system Si1-xGex/Si, we calculated the critical thicknesses for
elastic and plastic relaxation for the system Ge/Si1-xGex. In good agreement with those theoretical
considerations, we observe the beginning of plastic relaxation via the formation of misfit
dislocations after reaching a critical layer thickness regarding the force-balance model [3]. By
varying the composition of the VS, the critical thickness for strained Ge layers can be tuned,
making it applicable for high mobility channels.
Ge layers were grown on relaxed virtual Si1-xGex(001) substrates using SME. The samples were
characterized with HRXRD, GIXRD, TEM, SEM, AFM and Raman spectroscopy. For Ge on
Si0.22Ge0.78, it is between 10 and 20 nm and for Ge on Si0.31Ge0.69 between 5 and 10 nm,
respectively. TEM investigations show relaxation of the layers via the generation of misfit
dislocations (MDs) after reaching the critical thickness, confirming the change in lattice parameters
acquired by HRXRD / GIXRD (Fig. 1).
Regarding surface morphology, the need for a surfactant is confirmed to grow smooth layers.
The surfactant decreases the surface free energy of the film and reduces the diffusion length of
adatoms on the surface, thereby suppressing the island growth that would otherwise occur at the
chosen process temperature.
Figure 1. TEM weak beam dark field images of defect structures of SME-Ge/Si0.22Ge0.78 systems with
different Ge layer thicknesses. The onset of plastic relaxation via MD formation is observed.
References:
[1] M. L. Lee et al., J. Appl. Phys. 97(1) (2005) 011101.
[2] T.F. Wietler et al., Thin Solid Films 557: (2014) 27–30
[3] J. W. Matthews and A. E. Blakeslee., J. Cryst. Growth 27 (1974) 118 – 125.
S08-P26
Reconstruction phase transition c(4x4) - (1x3) on the (001)InSb surface
Bakarov Askhat*1, Galitsyn Yurij1, Mansurov Vladimir*1, Zhuravlev Konstantin1
1
Rzhanov Institute of Semiconductor Physics, ac.Lavretiev avenue, 13, Novosibirsk (Russia)
The (100) surface of InSb is the most common growth surface, forming a number of surface
reconstructions depending both on the ratio of the group III and V species present on the surface
and the substrate temperature. Compared to the more commonly studied GaAs(100) surface, studies
of the epitaxial growth and reconstructions of InSb(100) are relatively scarce.
In the present work the surface structures that are formed have been observed, using reflection
high energy electron diffraction (RHEED), both during epitaxial growth and under static conditions
(i.e. under Sb flux only). The observed surface structures are include a (4x3), a (7x5), a c(4x4) and
an asymmetric (1x3). Usually the epitaxial growth is started on the c(4x4) surface (under Sb flux)
and the surface structure is transform to (1x3) reconstruction after onset of the In flux. The
reconstruction phase transition c(4x4) - (1x3) is investigated in details as a functions of the substrate
temperature and of the Sb flux. The intensity of inherent fractional spots of the c(4x4) phase was
measured during variation of these parameters.
It was experimentally found that at temperatures T<395°C there is a clear hysteresis for the
isotherms recorded during direct and reverse Sb flux variation, as it shown in Figure 1, i.e. there is
an evidence that the transition c(4x4) - (1x3) is discontinuous (first order transition). However, the
hysteresis is not observed at temperatures T>395ºC (see Figure 1, the isotherm at 402ºC).
Previously, the transition c(4x4) - (1x3) was discussed in the work [1] as a continuous orderdisorder transition, and authors have reported 3 critical temperatures for the 3 different fluxes of Sb.
However, it is clear that the transition is induced by the Sb adsorption onto the surface and only one
critical temperature exists. We have developed a model to describe the transition in frame of the
lattice gas approximation. This model takes into account the stabilization energy as result of Sb
dimers formation on the c(4x4) phase and lateral repulsion between the nearest neighboring Sb
dimmers.
Figure 1. Phase transition c(44) - (14) as function of Sb flux at different temperatures. Theta – the coverage of
the InSb surface by Sb dimmers.
The research was supported by a grant of Ministry of Education of the Russian Federation
RFMEFI60414X0134.
References:
[1] Nigel Jones, PhD thesis, “The Atomic Structure of the Indium Antimonide (001) Surface”, Department of
Physics and Astronomy University of Leicester. (1998) pp.102-120.
SESSION 9
Fundamentals - Structural Defects and their characterization in Crystalline Materials
Cellular dislocation patterns in “Mono-like” silicon grown by seeded directional
solidification of the melt
Vanessa Amaral de Oliveira12*, Marina Rocha1, Thu-Nhi-Tran-Thi3, Maria Tsoutsouva3, José Baruchel3,
Denis Camel1
1
Université Grenoble Alpes, CEA-INES, Savoie Technolac, F-73375 Le Bourget-du-Lac (France)
2
ECM Greentech, 109 rue Hilaire du Chardonnet, 38100 Grenoble (France)
3
European Synchrotron Radiation Facility, BP 220, F-38043 Grenoble Cedex 9 (France)
Mono-like silicon growth has recently been established as a low cost alternative for the growth of
monocrystalline ingots. With the use of an extended monocrystalline seed layer at the bottom of the crucible,
silicon grows by directional solidification with the same orientation of the seeds. Despite the best mono-like
solar cells achieve efficiencies close to Cz-Si based cells, average mono-like Si efficiencies are still limited
by the presence of structural defects such as dislocations.
Dislocations arranged in cellular patterns can be observed in the entire mono-like Si ingot. This cellular
structure is composed by dense walls of immobile dislocations formed by cross-slip and short range
interactions between dislocations. The walls are separated by almost dislocation free domains including few
mobile dislocations produced by deformation that will be blocked or annihilated at the dislocated wall during
annealing at high temperature. P. Rudolph [1] studied this structure in as-grown semiconductor crystals and
correlated the cell dimension with the dislocation density and the local thermo-mechanical stress. It was also
observed that doping (for instance with In in GaAs) can lead to the suppression of those cellular patterns [2].
In the present work, Synchrotron radiation X-ray White-beam Topography and Rocking Curve Imaging
(RCI) is applied to visualize the dislocation arrangements and to quantify the spatial distribution of the
associated lattice distortions. RCI peak position mapping shows a very small crystal mosaicity with tilt
angles between cells smaller than 3 arcseconds. The cells are present in higher densities inside the seeds (cell
diameter of 300 µm and dislocation density estimated as 105 cm-2 in its wall). As growth proceeds, the cell
size increases and the dislocation density decreases varying from 5 × 104 cm-2 to 1 × 104 cm-2 according to the
zone of the ingot.
In order to understand the influence of parameters as silicon doping, stress and time under stress on the
formation of cells, a comparative study was started on the dislocation structures obtained by crystallization
of conventional as well as Ge doped (1020 at.cm-3) Si ingots, and by annealing under imposed stress with a 4point bending test device accommodated inside a DSS furnace. The bending tests were carried with
specimens of pure and Ge-doped silicon single crystals at 1300°C, using stress of 1 MPa and 5 MPa and time
under stress of 2h and 10h. The first results show changes in the cellular network in Ge-doped silicon,
probably related with local lattice deformation that affects the dislocation dynamics. On this basis, a
discussion is made of the dynamics of formation of the final dislocation arrangement.
b)
a)
c)
100 µm
1 mm
Figure 1. a) Cellular patterns in the bottom of a mono-like ingot. b) Cell structure visualized by RCI. c)RCI integrated intensity change at cell walls
(higher intensities) and at cell core (lower intensities).
References:
[1] P. Rudolph., Cryst. Res. Technol. 40, No. 1/2, (2005) 7-20
[2] H. Ono., Journal of Crystal Growth.89 (1988) 209-219
Nonstoichiometry problems of AIIBVI vapor grown crystals
Igor Avetissov*1, Andrew Khomyakov1, Albert Davydov2, Elena Mozhevitina1, Vladimir Chegnov2,
Nikolai Zhavoronkov2
1
2
Research Institute of Material Science and Technology, Proezd 4806, build.2, Zelenograd Moscow (Russia)
AIIBVI single crystals have a number of unique properties which significantly depend on nanoscale defect type and concentration. Native point defects generating as a result of deviation from
stoichiometric composition influence on luminescence, conductivity, and other structure sensitive
properties in the same manner as dopants. Raising the level of purity of modern semiconducting
materials results to the need of nonstoichiometry control in single crystals, thin films,
polycrystalline powders, etc. At the same time the new level of purity of semiconductors needs to
check and revise the literature data of nonstoichiometry.
In the research we have examined extra pure 50-100 mm diameter CdTe, ZnTe, ZnSe, CdSe,
CdS single crystals grown from vapor by Davydov-Markov technique [1]. Impurity and
nonstoichiometry distributions have been analyzed by ICP-MS and «extraction» techniques [2],
correspondingly.
The correlation between equilibrium P-T-x diagrams and crystal's nonstoichiometry has been
discussed. It was proved that in some cases the electrically neutral native point defects were
dominant in the analyzed crystals. The generalized scheme of nonostoichiometic defects in AIIBVI
compounds has been elaborated.
Figure 1. ZnTe, CdTe and ZnSe single crystals grown by Davydov-Markov technique [1]
References:
[1] Davydov A., Markov E., Khryapov V., Izvestia Akad. Nauk SSSR, Neorg. Mater. 16(12) (1992) 2119
[2] Avetissov I., Mozhevitina E., Khomyakov A., Tran Khanh, Cryst. Res. Technol. 50 (2015) N 1, 93–100
Influence of growth conditions on the optical, mechanical and electrophysical
properties the lanthanum-gallium silicate group crystals
Buzanov Oleg1, Kozlova Nina2, Kozlova Anna2*, Zabelina Evgeniya2, Siminel Nikita,2 Spassky Dmitriy3,4
1
2
OAO Fomos Materials, 119049 Moscow, Buzheninova st., 16 (Russia)
National University of Science and Technology “MISiS”, 119049, Moscow, Leninsky pr., 4 (Russia)
3
Institute of Physics, University of Tartu, Ravila 14c, 50411, Tartu, Estonia
4
Skobeltsyn Institute of Nuclear Physics, Moscow State University, Moscow, Russia
Lanthanum – gallium tantalate La3Ta0.5Ga5.5O14 (langatate) and lanthanum – gallium silicate
La3Ga5SiO14 (langasite) are the crystals with the structure of the Сa-gallogermanate. The space group of
symmetry is P321. High values of piezoelectric coefficient and thermostable cuts allowed to apply the
langasite for creating filters and resonators on surface and bulk acoustic waves. The drift of the piezoelectric
coefficients is not observed in langatate in contrast to langasite and other piezomaterials therefore it is used
for high-temperature sensors of different physical values. To use in such high temperature sensors
langatate crystals are processed with different methods of machining (cutting, grinding, polishing).
Currently, the electrophysical properties of langatate crystals mechanical characteristics and
their dependence on the growth atmosphere have not been discussed much in the literature.
Accordingly, this study is concerned with the influence of the growth atmosphere on the optical
transmission spectra, mechanical and electrical properties of langatate and langasite crystals.
For this study the langatate and langasite crystals were grown from iridium crucibles by the
Czochralski process at Fomos-Materials, in the athmospheres of argon (Ar), argon with oxygen
(Ar+O2). Oxygen concentrations in the growth atmosphere were about 2% for langasite and <1, <2,
and ~2% for langatate.
In a crystal point defects and their complexes influence its color and its electrical behavior,
acting as color centers. Optical spectroscopy therefore represents a very sensitive tool to examine
point defects. The influence of different growth atmospheres on optic transmission spectra of the
crystals showed that decreasing of oxygen concentration in growth atmosphere of crystal lead to the
considerable improvement of their optical characteristics [1].
The measuring method of microhardness is effective used for estimation of mechanical
properties of the crystals. The microhardness of langatate crystals obtained in different growth
atmospheres was studied and microhardness anisotropy was found out.
Langatate measuring sensors designed to operate at high temperatures often suffer from surface
degradation beneath the current carrying coating, which is applied to a polar cut. The thermal and
thermal-frequency dependences of langatate electrophysical parameters in constant and alternating
electric fields in the temperature range 20-500 oC were investigated. The frequency dependences of
relative dielectric constant (ε11/ε0), admittance, tg δ depend on the growth atmosphere.
The langatate electrophysical properties in alternating electric field were analyzed by means of
impedance spectroscopy method. The equivalent circuits were constructed by using the method
with allowance for the electrochemical processes of a cell “electrode-crystal-electrode”. The
parameters of this electrochemical cell were determined; the input of different near-electrode
processes into electrophysical properties of LGT was estimated.
References:
[1] Kozlova N.S., Buzanov O.A., Zabelina E.V., Kozlova A.P., Siminel N.A., Russian Microelectronics,
V.40 (2011) №8, p. 562-566
Micro-structural characterization of directionally solidified eutectic oxides
Maya Cherif1, 2, Gourav Sen2,3, Vicky Vikram Das2,Laurent Carroz1, 3, Omar Benamara4, Michel Parlier5 and
Thierry Duffar*2
1
3
4
ILM,UMR 5306 CNRS, 69622 Villeurbanne, France
5
Onera, Chemin de la Hunière et des Joncherettes BP 80100, 91123 Palaiseau, France
2
These last decades, directionally solidified eutectic oxides have drawn attention due to their
very good mechanical properties at high temperature. Our study focuses on the directional
solidification of Al2O3-YAG-ZrO2 ternary eutectic by three different growth techniques: EFG,
Bridgman and Micro-Pulling down, allowing a large range of growth conditions such as growth rate
and temperature gradient. This material exhibits a complex, interconnected microstructure. The
microstructure has been characterized for all grown samples by SEM and high resolution microtomography. The eutectic spacing, the colonies size, the phase shape and continuity have been
calculated with different image processing using an open source software “Fiji”. The relevancy of
the calculated parameters and the influence of the growth conditions have been investigated by
statistical methods (analysis of variance, Student test...).
Towards bulk cubic silicon carbide: Growth mechanisms and related defects
Rositsa Yakimova
Linkoping Inuversity, Linkoping (Sweden)
Among more than 200 polytypes, cubic (3C) SiC is the only one exhibiting smaller band gap and
isotropic crystal structure, respectively properties. This makes it very attractive for development of
metal–oxide–semiconductor field-effect transistors, high efficiency solar cells, biocompatible
medical devices or biomarkers. Furthermore, it is a perfect substrate for the growth of nitride and
epitaxial graphene layers.
However, 3C SiC is a metastable phase and it is very difficult to control its growth. Bulk crystal
growth has not been successful until now and this material has been mainly grown on Si or
hexagonal SiC substrates. In these cases a lot of defects are formed which deteriorate the grown
material quality.
In this talk we will summarize state of the art results showing the progress in recent understanding
of growth mechanism of cubic SiC on hexagonal SiC with a flat and stepped surface (on- and off
axis) aiming at developing bulk-like crystals. Growth mechanisms are different, while some
common defects appear mainly related to the 3C development on hexagonal type structure. Defect
formation accompanying polytype transformation and enlargement of initially nucleated domains
will be elucidated by using optical microscopy, Raman spectroscopy, Photoluminescence,
preferential etching and Transmission Electron Microscopy. It will be evidenced that structural
evolution can be mediated and controlled by selecting substrates and specific growth conditions.
Second-phase particle migration via Temperature Gradient Zone Melting
Kerry Wang, Andrew Yeckel, and Jeffrey J. Derby*
Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis, MN 55455, U.S.A.
Crystals of compound semiconductors, such as cadmium telluride, typically exhibit populations
of second-phase particles that can be deleterious to device performance. While the formation
mechanisms of larger particles are not well understood, their general presence is unavoidable due to
the room-temperature supersaturation of one species, caused by off-stoichiometry composition and
configurational entropic effects during growth from the liquid phase.
As an alternative to preventing particle formation during growth (which may not be possible), a
post-growth treatment may provide higher-quality crystals. Namely, large, secondary-phase
particles can be induced to move, leaving regions that contain far fewer particles. This
accomplished by heating the sample to slightly above the eutectic temperature (the melting point of
the second-phase particles) and applying a temperature gradient across the sample. Under such
conditions, the now-liquid particle dissolves on the hot side and re-solidifies on the cool side, with a
net effect of migrating toward the hotter region.
This phenomenon is termed “temperature gradient zone melting,” or TGZM. Historically, its
discovery was motivated by the experience of Arctic explorers, who found that newly formed sea
ice was not potable due to brine inclusions. However, after 2-3 years of exposure to sunlight, this
sea ice could be used for drinking water. In the aging process, brine inclusions migrate to the
surface by diurnal heating, thus purifying the ice. Tiller in 1963 devised the first approximate
mathematical model to describe inclusion migration via TGZM.
In this presentation, we present the formulation of mathematical models for particle migration
via TGZM. We demonstrate that an approximate analytical solution to this model in one spatial
dimension well describes the general behavior of particle migration. The analytical solution shows
that steady-state migration is not possible, and that, under a constant thermal gradient, the particle
velocity and size increase continually with time. Experimental observations are consistent with
these predictions. We also describe the implementation of a moving-boundary, finite-element
method that solves the model equations with no simplifying assumptions about mechanistic
interactions. Initial results provide excellent predictions of particle migration in cadmium telluride.
Figure 1. The model for particle migration in a thermal gradient is shown on the left. Computed results for a spherical
tellurium particle migrating through solid cadmium telluride are displayed on the right.
_________________
This research was supported in part by the U.S. Department of Homeland Security, 2012-DN077-ARI066-02; no official endorsement should be inferred.
Effects of Annealing Treatments on Microstructures of Aluminum Nitride
Buffer Layer Grown by MOVPE
Kuwano Noriyuki*1, Kaur Jesbains1, Fukuda Junya2, Soejima Yohei2, Mitsuhara Masatoshi3, Suzuki Shuhei4,
Miyake Hideto5, Hiramatsu Kazumasa4 and Fukuyama Hiroyuki6)
1
MJIIT, Universiti Teknologi Malaysia, Jalan Sultan Yahya Petra, 54100 Kuala Lumpur (Malaysia)
2
Dept. Appl. Sci. Electr. Mater., Kyushu University, Kasuga Fukuoka 816-8580 (Japan)
3
Dept. Eng. Sci. Electr. Mater., Kyushu University, Kasuga Fukuoka 816-8580 (Japan)
4
Dept. Elect. Electr. Eng., Mie University, 1577 Kurimamachiya-cho Tsu city, Mie 514-8507 (Japan)
5
Grad. Sch. Regional Innovation Studies, Mie University, 1577 Kurimamachiya-cho Tsu city, Mie 514-8507 (Japan)
6
IMRAM, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577 (Japan)
*[email protected]
In order to grow a high quality aluminum nitride (AlN) thin layer, it is essential to prepare good
quality AlN templates for overgrowth. In the present work, the microstructure in AlN buffer layers
fabricated on a sapphire substrate was characterized by electron microscopy, and the changes in
defect structure with the heat-treatment for the sapphire substrate and the deposited AlN buffer
layer were investigated to seek the growth process for high quality AlN.
AlN was deposited on a (0001) sapphire substrate by MOVPE method with TMA and NH3.
First, the sapphire substrate was annealing for surface cleaning under H2 atmosphere at Tcl and then
an AlN buffer layer about 100 nm thick was deposited at about 1200oC. Thereafter, an AlN layer
was overgrown on the buffer layer at 1500oC to be about 1μm in thickness. Some templates of the
buffer layer were annealed at Tan under the atmosphere of (CO + N2) before deposition of AlN
layer. Specimens for SEM and TEM observation were made using a focused ion beam (FIB) mill
and an Ar ion mill. Observation was conducted with JEM-2000EX, JEM-ARM and Ultra55. EBSD
analysis, AFM observation and X-ray rocking curve (XRC) measurements were also performed.
It was found that XRC of hkl=102 starts to increase in line width (FWHM) at 1250oC and is
split to two peaks above 1300oC. These changes in XRC are due to formation of twisting domains.
TEM observation confirmed that there are two types of twisting domains. Domains about 50-80 nm
in diameter arranged alternately in a regular way, and those of an oval shape about 0.5 ×1.5 μm,
composed with those of the former type. The results suggest that the formation of twisting domains
have two different origins; the (0001) surface and the step walls of sapphire substrate, respectively.
When Tcl is lower than 1200oC, twisting domains do not appear but inversion-regions are
formed near the interface of AlN/sapphire. Columnar inversion domains are developed up to the top
surface of AlN layer. The origin for inversion region is not yet clarified but oxygen atoms are
thought to play important role in growth process including the formation of Al(N,O).
There are several types of defects in AlN layer to be taken into account: threading dislocations,
twisting domains and inversion domains as well as surface morphology. Fortunately stacking faults
are not formed in the present AlN layers. It is not easy to decrease these lattice defects at one time
under a single condition of growth process: For example, when the growth temperature is raised in
order to decrease the density of dislocations, inversion domains are developed and the surface
becomes rough in morphology. In the course of investigation of process-optimization, it was found
that a high quality AlN layer was successfully grown on an AlN buffer layer after annealing at high
temperature. TEM observation confirmed that by annealing at 1500oC for 2 hr, the inversion regions
in an AlN buffer layer have changed to be domains of turned cone shape, and at 1550oC the
inversion domains coalesce with each other, leaving a single inversion domain boundary that runs
parallel to the top surface. The results show that annealing is a very effective treatment for
microstructure control even for semiconductor crystals.
The role of screw dislocations in habit modification of KDP by impurity
Xiaojun Lai 1, Kevin Roberts 1 and Helmut Klapper 2
1
Institute of Particle Science and Engineering and Institute of Process Research and Development, School of Chemical
and Process Engineering, University of Leeds, LS2 9JT, UK
2 Institute of Crystallography, RWTH Aachen University, D-52056 Aachen, Germany
[email protected]
Crystal habit modification by impurities is of fundamental challenge concerning with industrial
crystallisation processes. In the complicated process systems, some chemical components often serve as
impurities resulting in undesired crystal morphologies. On the other hand, some research has demonstrated
optimizing crystal shape by employing habit modifying additives to control the relative growth rates of the
crystal surfaces, such as using attachment energy, to predict the growth rates of the crystal habit faces.
However, only very few systems have, as yet, been fully studied. The problems concerning the physical and
chemical processes associated with such habit modifying agents remain largely unknown at this time, e.g. the
impurity structure and bonding in the crystal, and growth mechanisms of crystal habit faces with presence of
the impurities.
In this research potassium dihydrogen phosphate (KH2PO4, KDP) is investigated as a representative
system. Large single crystals of KDP were grown by solution cooling in presence of Cr3+ or Mn3+. The crystals
are elongated on [001] direction and (100) prismatic faces became tapering through the impurity incorporation.
The impurity structure as a form of transition metal complex and the chemistry associated with its
incorporation, have been characterized by x-ray spectroscopy/diffraction techniques in our previous study. [2]
X-ray topography is used to investigate the crystal defects in order for the mechanism of the crystal
tapering. Screw dislocations with the Burger’s vectors are characterized with respect to their types and line
directions. The growth history in the images of x-ray topographs shows that the tapering shape of (100) faces
was formed during the fast growth of the (101) faces; this tapering angle was reduced and finally disappeared
when the relative growth rate of the (101) slowed down. The x-ray topography provides the evidence of
dislocations undergoing their redistribution from the (101) growth sector to the (100) sectors due to the
elongated shape derived. Therefore, the growth kinetics of (101) faces switches from the spiral growth step to
the 2-d surface birth & spread. The step growing directions and rates determined by the screw dislocations on
the (100) and (101) faces play the critical role in growth layers’ coverage at the boundary between the growth
faces or sectors, and hence determine the formation of the tapering morphology of KDP.
References:
[1]
Hammond R. B., et al, CrystEngComm, 2011, 13, 4935
[2]
Lan Z., Lai X., et al, Cryst. Growth Des. 2014, 14, 6084
The role of twin boundaries in growth of natural and Fe-doped SnO2 crystals
Sara Tominc*1, 2, Nina Daneu1, Aleksander Rečnik1
1
Jožef Stefan Institute, Jamova 39, Ljubljana (Slovenia)
Jožef Stefan International Postgraduate School, Jamova 39, Ljubljana (Slovenia)
2
According to a number of studies, cassiterite (SnO2) is an attractive material for a wide range of
applications such as solid-state gas sensors, surge arrestors (varistors), transparent conductors, solar
cells, catalysts and others [1]. In most of these applications, it is essential to control the crystal
growth and evolution of the microstructure. One of the main future objectives involves chemicallyinduced twinning that offers a wide range of possibilities to grow complex branched architectures
with tunable physical properties.
The main challenge of this work will be to determine whether the cause of twinning in SnO2 is
topotaxial growth on still unknown precursor material, or is the source tropochemical. The principle
will be verified by reproducing the twinning under constrained laboratory conditions. To understand
the twinning mechanism we first investigated natural twins of cassiterite from Viloco mine near La
Paz in Bolivia. Samples for transmission electron microscopy (TEM) studies were prepared from
natural twins along low index zone axes, [010] and [101]. Energy dispersive spectroscopy (EDS)
analysis confirmed that the twin boundaries are genetically related to the presence of Fe. The twin
boundary is characterized by numerous oriented Fe-rich inclusions, located at the {101} twin
boundary and also in bulk cassiterite. Using selected area electron diffraction (SAED) analysis and
Fourier transforms (FFT) from HRTEM images recorded along the twin boundary, we confirmed
that both symmetry and d-spacings of these precipitates best correspond to magnetite (Fe3O4). To
reproduce twinning in laboratory, we prepared SnO2-based ceramics with the addition of 1 mol %
of iron oxide (Fe2O3). The samples were sintered at 1300 °C for 5 hours and thermally etched at
1250 °C for 15 minutes to reveal the microstructure. Polished cross-sections of the samples were
characterized using optical and scanning electron microscopy (SEM). Further TEM investigations
will be applied to confirm whether the Fe-rich additives in fact trigger the formation of twin
boundaries in SnO2.
Figure 1: (a) Low magnification TEM image of (natural cassiterite twin with corresponding experimental diffraction
pattern. (b) SnO2 ceramics doped with 1 mol % Fe2O3 displaying twinned crystals.
References:
[1] Parra R., Ramajo L.A., Góes M.S., Varela J.A., Castro M.S.., Mat. Res. Bull. 43 (2008) 3202-3211.
POSTER
S09-P03
Study of charge compensating defects in BaF2:YbF3 crystals using
dielectric relaxation
Irina Nicoara1*, Marius Stef1, Octavian Bunoiu 1
1
West University of Timisoara, Dept. of Physics, Bd. V. Parvan nr 4, Timisoara, Romania
Barium fluoride crystal finds applications as a transmitting window over a wide wavelength
range, as a fast scintillator involving emission at 195 nm and 220 nm and doped with rare-earth
(RE) ions as laser material. The RE3+-ions usually occupy a cation substitutional position in BaF2
lattice and charge compensation is required to maintain the electrical neutrality of the system. The
extra positive charge is compensated by an interstitial fluorine ion. This indeed leads to a complex
site structure including so-called isolated ions, pairs (or dimers) of adjacent rare-earth ions, clusters,
etc., depending on the nature of the substituted cation, of the RE dopant and of the dopant
concentration. In order to understand the spectroscopic properties of the crystals it is important to
know the type of the charge compensating defects that are format.
Local compensation by pairing of Yb3+ ions with interstitial F– ions create electric dipoles
whose relaxation are observed as dielectric absorption. Temperature and frequency dependence of
the complex dielectric constant (the dielectric spectrum) gives information about the impuritydefect aggregates [1, 2].
The goal of this work is to study the dielectric spectra of the YbF3-doped BaF2 crystals in order
to obtain information about the impurity-defect formation in these crystals.
Various concentrations YbF3 -doped BaF2 (0.05, 0.1, 0.2 mol% YbF3) crystals have been grown
using the conventional Bridgman method. Transparent colorless crystals of about 10 mm in
diameter over 5-6 cm long were obtained in graphite crucible in vacuum (~ 10-1 Pa) using a shaped
graphite furnace [3], the pulling rate was 4mm/h. The optical absorption spectra reveal the existence
of both Yb2+ and Yb3+ ions.
The dielectric measurements were performed using a RLC Meter ZM 2355, over the temperature
range 150–300 K, at nine audio-frequencies 1–100 kHz. The real part of the dielectric constant, ε1,
has been calculated from the measured capacitance. The ε2 has been then calculated from D= ε2/ ε1
(D = tan δ is the dielectric loss). The relaxation parameters (the activation energy for dipole
reorientation and relaxation time constant) have been calculated in order to characterize the observed
relaxations. We assign the observed relaxation to trigonal type (C3v) centres. The number of the
dipoles, ND , that contribute to the dielectric relaxation have been determined from the dielectric
spectra; the correlation between ND and the optical spectra has been also discussed. A comparison of
dielectric spectra of CaF2:YbF3 and BaF2:YbF3 crystals is also given.
Acknowledgment. This work was supported by the Romanian Ministry of Education and
Research, grant ELICRYS, Contract nr.13/30.06.2014 in the frame of Capacities/RO-CERN (ELINP) Program.
References:
[1] J. Fontanella and D. J. Treacy, J. Chem. Phys. 72 (1980) 2235,
[2] I. Nicoara and M. Stef, Eur. Phys. J. B (2012) 85:180 DOI: 10.1140/epjb/e2012-20914-8
[3] D. Nicoara and I. Nicoara, Mater. Sci. Eng. A 102 (1988) L1.
S09-P04
Some optical properties of YbF3 doped BaF2 crystals
Irina Nicoara1*, Marius Stef1, OctavianBunoiu 1
1
West University of Timisoara, Dept. of Physics, Bd. V. Parvan nr 4, Timisoara, Romania
In the last time the interest in rare-earth (RE)-doped MeF2 (Me= Ca, Sr, Ba) crystals used as
laser material is still growing due to the well known good optical characteristics of the fluorite host.
The Ytterbium ions are most easily stabilized as trivalent ions in MeF2 crystals, the divalent state
has certain distinct advantages for laser applications [1, 2]. The properties of low concentration
YbF3 doped BaF2 crystals have been less investigated than the other RE doped BaF2 crystals [3].
In this work we report the growth and some optical properties of YbF3- doped BaF2 crystals
with high concentration of divalent Yb ions obtained without any other treatment. Ba1-xYbx F2-x (x =
0.0005, 0.001 and 0.002) crystals have been grown using the conventional Bridgman technique.
Transparent colorless crystals of about 10 mm in diameter over 5-6 cm long were obtained in
graphite crucible in vacuum (~ 10-1 Pa) using a shaped graphite furnace [4]; the pulling rate was 4
mm/h. The goal of this work is to study the optical absorbtion spectra of low YbF3 concentration
doped BaF2 crystals in order to obtain information about the impurity-defects formation.
It is known that the optical properties of the crystals depend on the Yb2+ , Yb,3+ and F- ions
positions in the lattice. The Yb3+ ions substitute for Ba2+ ions and need charge compensation
obtained by an interstitial fluoride ion located in various positions giving rise to a rich multisite
structure, which leads to broad absorption bands. The Yb2+ ions substitute for Ba2+ ions, do not
need charge compensation and posses cubic symmetry. The optical absorption spectra of our
crystals reveal the existence of both Yb2+ (in the near-UV) and Yb3+ ions (in near-IR domain).
These spectra are characterized by a very broad band in near-IR domain, corresponding to the 2F7/2
-2F5/2 transitions of the Yb3+ ions [3, 5]. Unlike the spectra of high YbF3 concentration crystals
[16], in the case of our low concentration YbF3 doped BaF3 crystals three principal maxima (928 ,
968 and 974 nm) and four weak peaks have been observed. In each case the dominant peak is at 968
nm. Taking into account our dielectric relaxation measuremets we assign this peak to C3v centre,
with the charge compensating interstitial F- ion occupying a next-nearest neighbor position in a
[111] direction from the Yb3+ ion. As the YbF3 concentration inceases the intensity of the second
peak at 974 nm (assigned to clusters, CR) [3] increases. The intensity ratio between these two
peaks (CR/C3v) increases as the concentration increases: 0.5, 0.7 and 1.1.The peak at 928 nm
corresponds to the centre with cubic (Oh ) symmetry, and the small peaks are associated with other
defects where the charge compensation is provided, probably, by oxygen impurities or/and to
marginal population of Yb3+ ions in other symmetries.
Acknowledgment. This work was supported by the Romanian Ministry of Education and
Research, grant ELICRYS, Contract nr.13/30.06.2014 in the frame of Capacities/RO-CERN (ELINP) program.
References:
[1] A. A. Kaplyanskii et al., Opt. Spectrosc. 41 (1976) 615,
[2] B. Moine, B. Courtois and C. Pedrini J. Physique 50 (1989) 2105
[3] D. Camy, J. Doualan, A. Benayad, M von Edlinger, V. Menard and R. Moncorge, Appl. Phys. B
89 (2007) 539
[4] D. Nicoara and I. Nicoara, Mater. Sci. Eng. A 102 (1988) L1
[5] J. Kirton and S.D. McLaughlan, Phys. Rev. 155 (1967) 279.
S09-P05
Interplay mechanism of secondary phase particles and the extended dislocations
in CdZnTe crystals
1
Yadong Xu1, 2*, Yihui He1, Ningbo Jia1, Rongrong Guo1, Yaxu Gu1, Yuecun Wang1, Wanqi Jie1
State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072, China
2
Laboratory of Solid State Microstructures, Nanjing University, 210093, China
The presence of SP particles often markedly affects the optical and electronic properties of the bulk crystals as well
as the surface perfection of epitaxial substrates. They appear not only in II-VI (e.g., CdTe, ZnSe), III-V (e.g., GaN), and
IV-VI (e.g., SiC) compounds, but also in oxides and fluorides. CdZnTe (CZT) crystals have been studied intensively
due to their potential applications in X/γ-ray detection and the growth of HgCdTe epilayers. However, localized regions
with SP particles (inclusions/precipitates) and induced dislocations are usually generated inevitably in as-grown or postgrowth annealed CZT crystals [1, 2], which are known to be detrimental to the charge collection for CZT detector,
simultaneously to degrade the epilayers crystallization. Therefore, it is meaningful to study the relationship between SP
particles and induced dislocations, in order to orient towards material with either better performance or lower
concentration defects.
To manifest the interplay mechanism between dislocations and Te-SP particles, dislocation arrangement
surrounding Te-SP in CZT crystals was investigated after isothermal and thermal gradient annealing under specific
atmospheres in this work. Employing defect-selective etching techniques, the distributions of Te-rich SP particles and
dislocations on CZT {111)}Te surfaces were observed using correlative reflected-light/IR transmission and scanning
electron microscopy (SEM). In addition, the extended defects of local areas were identified by transmission electron
microscopy (TEM) and cathodoluminescence (CL) microscopy. Two possible models for growth and multiplication of
dislocation clusters are proposed on the basis of dissociation-diffusion and thermomigration-deformation, respectively.
Figure 1. (a) SEM image of as-grown CZT {111}Te face after etching by Everson solution. (b) ‘Radial-shaped’ etch pits rosette
surrounding a Te-SP (c) Typical optical image of CZT {111}Te by defect-selective etching after 650 °C annealing. (b) ‘Star-shaped’
dislocation cluster.
Our investigations demonstrated that Te-rich SP particles are more efficiently eliminated under thermal gradient
annealing than that under isothermal annealing. However, ‘radial-shaped’ dislocation rosettes and ‘star-shaped’
dislocation clusters are observed more frequently after annealing under Cd/Zn atmosphere, as seen in Figures 1. The
driving forces which lead to the generation and multiplication of the dislocations rosette have been discussed.
During the isothermal annealing at Cd/Zn overpressure, Te-SP dissociation dominates the volume variation, which
results in the dislocations glide and climb systems activate, simultaneously with the diffusion of Tei. Then growth and
multiplication of the dislocations are enhanced by the thermal stress, which is attributed to the exothermic reaction
between Cd/Zn and Tei. A proposed model is demonstrated in Figures 2, which shows the evolution of Te-SP and the
surrounding etch pits rosette on {111}Te. However, for thermal gradient annealing, Te-SP migration towards the high
temperature side is superior to the dissociation. The recrystallization quality is related with the drift velocity of Te
droplets. Lattice deformation in CZT near surface region is accompanied by the dislocation multiplication due to the
severe misfit stress.
Figure 2. Diagram of the evolution of Te-SP and the surrounding etch pits rosette on {111}Te.
References:
[1] Yadong Xu, Yihui He, Tao Wang, et al., Investigation of Te inclusion induced glides and the corresponding dislocations in
CdZnTe crystal. Crystengcomm, 2012. 14(2): 417-420.
[2] Yihui He, Wanqi Jie, Yadong Xu, et al., Matrix-controlled morphology evolution of Te inclusions in CdZnTe single crystal.
Scripta Materialia, 2012. 67(1): 5-8.
S09-P06
Oxygen precipitation behavior in heavily arsenic doped silicon crystals
Stephan Haringer1, Daniela Gambaro2, Maria Porrini1*
1
MEMC Electronic Materials SpA, via Nazionale 59, 39012 Merano (Italy)
MEMC Electronic Materials SpA, viale Gherzi 31, 28100 Novara (Italy)
2
The behavior of oxygen precipitation in silicon has been studied for decades, and there is a vast
literature in this field [1]; however, most of the studies have concerned either lightly doped wafers
or heavily boron doped wafers. Very little information is available in the case of heavily doped Ntype silicon wafers, and especially for the large diameters and high concentration levels that are
becoming more and more requested nowadays by the expanding market of discrete devices.
Moreover, the few available papers examine commercial wafers, whose position in the crystal is not
specified, and for which no information on the previous thermal history is available [2, 3].
Purpose of this work is to contribute to the understanding of oxygen precipitation behavior in
large diameter, heavily arsenic doped silicon crystals grown with the Czochralski method.
Silicon crystals containing different levels of arsenic concentration and oxygen content were
grown, and samples were taken at various positions along the crystal, to study the influence of three
main factors, i.e. the initial oxygen content, the dopant concentration and the thermal history, on the
nucleation of oxygen precipitates during crystal growth and cooling in the puller. The crystal
thermal history was reconstructed by means of computer modeling, simulating the temperature
distribution in the crystal at several growth stages. The oxygen precipitation was characterized after
a thermal cycle of 4 h at 800°C for nuclei stabilization + 16 h at 1000°C for nuclei growth. Oxygen
precipitates (BMD) were counted under microscope on the cleaved sample surface after preferential
etching. Lightly doped silicon samples were also included, as reference.
Our results show that also in heavily arsenic doped silicon the oxygen precipitation is a strong
function of the initial oxygen concentration, similar to what has been observed for lightly doped
silicon. In addition, a precipitation retardation effect is observed in the arsenic doped samples when
the dopant concentration is higher than 1.7x1019 cm-3 compared to lightly doped samples with the
same initial oxygen content and crystal thermal history. Finally, a long permanence time of the
crystal in the temperature range between 450°C and 750°C enhances the oxygen precipitation,
showing that this is an effective temperature range for oxygen precipitation nucleation in heavily
arsenic doped silicon.
References:
[1] see for example: A. Borghesi, B. Pivac, A. Sassella, A. Stella, Journal of Applied Physics, 77(1995) 4169
– 4244
[2] W. Sugimura, T. Ono, S. Umeno, M. Hourai, K. Sueoka, ECS Transaction 2(2) (2006) 95 – 107
[3] Y. Zhao, D. Li, X. Ma, D. Yang, J. Phys.: Condens. Matter 16, (2004) 1539 – 1545
S09-P07
Blocks and Residual Stresses in Shaped Sapphire Single Crystals
Krymov V.M., Nosov Yu.G. , Bakholdin S.I., Maslov V.N., Shul’pina I.L., Nikolaev V.I.
Ioffe Institute, Politekhnicheskaya ul. 26, St. Petersburg, 194021 Russia
The single-crystal rods and tubes grown from the melt by the Stepanov (EFG) method are widely applied
in technology. In some cases of usage, such as seeds for bulk crystals growth or for the production of gasdischarge lamps, the crystals without blocks and residual stresses
are required.
The influence of seed crystallographic orientation, conditions of a seeding and thermal stresses on the
development of blocks and residual stresses in the crystals of various forms has been studied. Sapphire rods
of circular (diameter of 8, 12 and 23 mm) and square (8х8) mm cross sections and tubes (10x8), (27x10) and
(16х9) mm were grown. The block structure of the grown crystals has been studied by the polarization-optical
method and X-ray diffraction topography.
Сrystallographic orientation. It is shown that in most cases, at growth of sapphire rod
in the c direction - along the optical axis [0001], the block - mosaic structure is formed . The initial part of such
crystal contains separate large blocks. In the process of a crystal growth the ring-shaped development of block
structure from a crystal surface to the center with reduction of the block sizes is observed. It has been found
that when rods are being grown in the a direction [2 1 1 0], the structural perfection of crystals is higher and
local near-surface blocks are formed only rarely. For the tubular form crystals grown in the a direction the
strong development of blocks in the areas of the presence of two (0001) faces on a lateral crystal surface is
observed.
The formation of block structure in cross section and along the length in c direction tubes is similar to the rods
of the same orientation.
Seeding. Block-free single crystal rods of both orientations with the diameter up to 20 mm can be obtained
using a block-free seed and with the exact thermal mode of a seeding. However when the crystal diameter
exceeds 20 mm, the thermal stresses are increased and blocks nucleation in c crystals is possible even when
a block-free seed is used and thermal seeding conditions are fulfilled.
Thermal stresses. The residual stresses in cross sections of the sapphire [0001] crystals have been
studied using the optical konoskopiya method. Both the rod of circular section 23 mm in diameter and the tube
27x10 mm have been investigated. The difference of stresses (σφ-σr) in rod is minimum in the central part and
is increased to its periphery. The maximum tensile stresses act at a rod surface. Their value doesn’t exceed
20 MPa. The difference (σφ-σr) for tubular single crystals reaches the maximum values 15-20 MPa at external
and internal surfaces. It has been shown that the tensile stresses act at the external surface of tube whereas
the compression stresses act at its internal surface.
The comparison of the measured residual stresses distribution and calculated thermal stresses allowed to
come to the conclusion that imperfect structure and residual stresses are caused by plastic deformation of the
grown crystal in a very restricted high-temperature area (height about 1 mm) from the crystallization front.
References:
[1] Krymov V.M., Nosov Yu.G., Bakholdin S.I, Maslov V.N., Shul’pina I.L., Crystallography Reports, Vol. 60, (2015), p. 377.
[2] Krymov V.M., Nosov Yu.G., Bakholdin S.I, Galaktionov E.V., Maslov V.N., Tropp E.A., Physics of the Solid State, Vol. 57, (2015),
p.746.
S09-P08
Strain Energy Analysis of Screw Dislocations in 4H-SiC by Molecular Dynamics
Takahiro Kawamura*1, Mitsutoshi Mizutani1, Yasuyuki Suzuki1, Yoshihiro Kangawa2, Koichi Kakimoto2
1
Graduate School of Engineering, Mie University, 1577 Kurimamachiya-cho, Tsu, 514-8507 (Japan)
Research Institute for Applied Mechanics, Kyushu University, 6-1 Kasuga-koen, Kasuga, Fukuoka 816-8580 (Japan)
2
Silicon carbide (SiC) is an attractive wide-gap semiconductor for fabricating high-power and
energy-conserving devices. It is known that crystal defects such as threading screw dislocation,
threading edge dislocation, stacking fault, etc. deteriorate the device performance [1]. To overcome
the problems, we need to understand the defect structure in detail. In this study, we analyzed strain
energy of screw dislocations in 4H-SiC using molecular dynamics simulation.
Simulation cell was composed of 614400 atoms and its size was 494330 (a-, m-, and c-axes)
nm3. The periodic boundary condition was applied along the c-axis direction. Atoms on the edge of
the simulation cell in the a- and m-axis directions were fixed. A dislocation core was set at the
center of the a-m plane and the burgers vector was parallel to the c-axis. We simulated screw
dislocations with Burgers vector (BV) = 1c, 3/4c, 1/2c, and 1/4c, where “c” is the thickness of four
atomic layers of SiC. Strain energy of each atom (Estrain) was defined by Estrain = Escrew  Eperfect,
where Estrain is the potential energy of the simulation model including a screw dislocation and Eperfect
is the potential energy of perfect crystal. The simulation time was 10 psec (10000 step) and the
temperature was set to 0 K. We used Brenner potential [2,3] to calculate interatomic forces.
Figure 1 shows the map of strain energy of each atom when the BV was 1/2c. We can see that
there was large strain at the dislocation core and the plane defect. The plane defect was observed
when the BV was 3/4c, 1/2c, and 1/4c. Figure 2 shows the total strain energy within a radius r from
the dislocation core. From the inset, it was found that the total strain energy caused by the
dislocation core increased with the BV. The values of 1c converged with increasing the radius. On
the other hand, in the large radius region, the values of 3/4c, 1/2c, and 1/4c were proportional to the
radius because of the contribution of the plane defect. Comparing the slope of the three graphs
(3/4c, 1/2c, and 1/4c), the slope of 1/2c was the smallest and those of 3/4c and 1/4c were almost the
same. This indicates that when the BV was 1/2c, the strain energy per unit area caused by the plane
defect was the smallest among the three cases.
Figure 1. Strain energy map
(Burgers vector = 1/2c)
Figure 2. Strain energy within a radius from the
dislocation core. The inset is the magnification in the
small radius region.
References:
[1] H. Fujiwara et al., Appl. Phys. Lett. 101 (2012) 042104.
[2] D. W. Brenner, Phys. Rev. B 42 (1990) 9458.
[3] A. J. Dyson and P. V. Smith, Molecular Physics 96 (1999) 1491.
S09-P09
STUDY OF DEFECT FORMATION IN KDP CRYSTALS UNDER HIGH SUPERSATURATION
Baskakova Svetlana*, Voloshin Alexey
Shubnikov Institute of Crystallography of RAS, Moscow, Russia
During crystal growth from aqueous solution the defect formation is determined mainly by processes
occurring on the growing face. If the mechanism of crystal growth is changed from the spiral one to the twodimensional (2D) nucleation it is expected the change of mechanism of defect formation. Growth of inorganic
crystals from aqueous solutions at low supersaturation has been studied by various authors in sufficient detail.
But due to the difficulties in crystal growth at high supersaturation in the water-salt systems, these issues at 2D
nucleation have never been studied. There are several articles, which describe X-ray topography investigation
of KDP crystals grown under high velocity [1-3]. But supersaturation in these experiments was not enough for
realization of 2D nucleation mechanism. In addition, there are a couple of articles on KDP crystal growth at
supersaturation 25 - 60% [4-5] but X-ray topographic studies were not conducted there. Thus, the data about
defect formation under 2D nucleation at high supersaturation are very poor and did not allow one to make the
complete picture. Therefore, this work is a study of the main types of defects and the mechanisms of their
formation in crystals grown from aqueous solutions at high supersaturation, when the growth is driven by 2D
nucleation. KDP crystal was taken as a model object.
Calculations of the KDP crystal growth kinetic curves show that domination of the 2D nucleation over the
dislocation spiral growth might be achieved at supersaturation higher than 20%. A series of KDP crystals was
grown at the supersaturation 25% and studied by X-ray topography. There are zonality of morphological type
and sub-sectorial boundaries, indicating the partial realization of spiral growth. At the supersaturation 35% and
40% dislocation beams and sectorial boundaries are visible on the performed topographs. Chaotic set of
strongly curved lines is seen in the prism sectors of the crystal grown at 40%. To study the zonal
inhomogeneity of KDP crystals under high supersaturation, the crystal was obtained with the change of
supersaturation from 35% to 38% during the growth (Figure 2, №3). The stripe continuous at all sector
boundaries was found on the crystal topograph, this is typical for crystals grown by 2D nucleation mechanism.
Finally, a crystal was grown at the supersaturation 60% (Figure 3). On the crystal topograph there are not
seen zonal inhomogeneity, sectorial borders are greatly weakened, dislocation bunches are completely absent
in the sector of the prism, a small bunch is observed in the sector of the pyramid.
The obtained results generally confirm the difference in the mechanisms of zonal inhomogeneity formation
under the spiral growth and 2D nucleation. But spiral growth at the supersaturation 40% still appears quite
noticeably affecting on the overall pattern of impurity distribution. However, the lack of zonal inhomogeneity
and reduction of the number of dislocations bunches at 60%, apparently, indicates the predominance of the 2D
nucleation mechanism over the spiral growth.
m).
This study was conducted with support from the Russian Foundation for Basic Research (grant No. 13-02-12163-ofi-
References:
[1] Zaitseva N.P., Smolski I.L., Rashkovich L.N. Crystallography 1 (1991) 36
[2] Smolski I.L., Zaitseva N.P. Crystal Growth, Volume 19.
[3] Zaitseva N.P., De Yoreo, Dehaven et al., Journal of Crystal Growth 180 (1997) 255
[4] Zaitseva N.P., Rashkovich L.N., Bogatyreva S.V. Journal of Crystal Growth 148 (1995) 276.
[5] Zaitseva N., Carman L., Smolski I., Torres R., Yan M. Journal of Crystal Growth 210 (1999) 512–524
S09-P10
Czochralski growth and characterization of rare earth-doped Gd3(Al,Ga)5O12
crystals
Ryba-Romanowski Witold *1, Komar Jarosław 1, Solarz Piotr 1, Jeżowski Andrzej1, Głowacki
Michał 2, Berkowski Marek 2
1
Institute of Low Temperature and Structure Research, Polish Academy of Sciences, Okolna 2, 50-422 Wrocław, Poland
2
Institute of Physics, Polish Academy of Sciences, Al. Lotników, 32/46, 02- 668, Warsaw, Poland
*[email protected]
Among a large family of substituted garnets employed as hosts for luminescent rare earth ions
the Gd3(Al,Ga)5O12 system is the newest one. Originally proposed for the design of Ce3+-doped
scintillating material [1], it is able to accommodate other rare earth ions offering thereby a potential
for developing new phosphors and laser materials. In the present work we consider peculiarities of
point defects consisting of intentionally incorporated impurities or unintentional colour centres and
their effect on macroscopic features of this disordered system. Solid solution crystals with nominal
stoichiometry Gd3Al2.5Ga2.5O12 doped with Sm3+, Dy3+, Ho3+, Er3+ and Yb3+ were grown by the
Czochralski method using a Malvern MSR4 puller with an automatic diameter control based on
weighting the crucible. Starting oxides were dried at 1000 C for 4 hours before weighting.
Powders in appropriate molar ratios were mixed together and then pressed into cylindrical pellets
under pressure of 200 kPa and calcinated at 1350 C for 6 hours before melting in crucible. Single
crystals were grown under nitrogen atmosphere on <111> oriented seeds with a pulling rate of 2.5
mm/h and a speed of rotation 20 rpm. Transparent crystals with 20 mm of the diameter and 60 mm
in length were grown with a convex crystal melt interface from inductively heated iridium crucible
of 40 mm in diameter. Recorded optical absorption spectra revealed that the intensity and spectral
characteristics of colour centre absorption in the UV region, close to the UV absorption edge of the
host, are affected by the type of incorporated rare earth ions and their concentration. On the other
hand, spectral characteristics of stable colour centres induced by an intense UV irradiation of
crystals depend weakly on the rare earth admixture. Low temperature optical spectra revealed that
widths of spectral lines related to transitions between individual crystal field levels of rare earth
ions are larger by a factor of four roughly, as compared to those encountered in ordered lattice of
yttrium aluminum garnet. Also, low temperature optical spectra indicate that Sm3+ ions in this host
occupy at least two different types of sites but much smaller Ho3+ and Yb3+ ions seem to be located
preferentially in identical sites. Thermal conductivity of crystals doped with holmium or ytterbium,
close to 7.9 W/mK at 300K, increases to 32 W/mK at 77 K and next, at lower temperature becomes
anomalously affected by concentration of incorporated ions. Further examination of the systems
under study is in progress to elucidate this puzzling observation.
References:
[1]. K. Kamada, T. Yanagida, T. Endo, K. Tsutumi, Y. Usuki, M. Nikl, Y. Fujimoto, A. Fukabori,
A. Yoshikawa, J. Crystal Growth, 351 (2012) 88-90
S09-P11
Nonstoichiometry and luminescent properties of ZnSe crystals grown from the
melt at high pressures
Khan Tran1, Elena Mozhevitina1, Andrew Khomyakov1, Roman Avetisov*1, Albert Davydov2,
Vladimir Chegnov2, Vladimir Antonov2, Svetlana Kobeleva3, Nikolai Zhavoronkov2, Igor Avetissov1
1
2
Research Institute of Material Science and Technology, Proezd 4806, build.2, Zelenograd Moscow (Russia)
3
National University of Science and Technology, Leninsky prospect,4,Moscow (Russia)
AIIBVI single crystals have a number of unique properties which significantly depend on nanoscale defect type and concentration. Native point defects generating as a result of deviation from
stoichiometric composition influence on luminescence, conductivity, and other structure sensitive
properties similar to dopants.
ZnSe 50 mm diameter crystals have been grown from the melt at 100 at argon pressure in
graphite and glassy carbon crucibles. 3D impurities concentration and nonstoichiometry mapping in
the grown crystals (Fig.1) have been fulfilled by ICP-MS and «extraction» techniques [1],
correspondingly.
Depending on the growth conditions and crucible material the crystal had overstoichiometric
(excess) Se concentration which was in several orders less than the concentration at the
homogeneity limits.
We established the dependence of Se excess concentration on temperature and Se partial
pressure within the homogeneity limits at Ss-ZnSeV bivariant equilibrium. The processing of the
experimental data on the Se solubility in nonstoichiometric s-ZnSe (zinc blend) showed that in the
framework of the quasi-chemical theory of defect generation the data have been adequately
described, considering the generation of clusters (associates) based on electrically neutral vacancies
in zinc sublattice followed by exothermic reactions.
The research was supported by the Russian Science Foundation grant N 15-13-10028
Figure 1. ZnSe crystal grown by from the melt at PAr=100 atm in a graphite crucible
References:
[1] Avetissov I., Mozhevitina E., Khomyakov A., Tran Khanh, Cryst. Res. Technol. 50 (2015) N 1, 93–100
S09-P12
Nonstoichiometry and luminescent properties of
tris(8-hydroxyquinoline)aluminum crystals
Igor Avetissov, Alina Akkuzina, Roman Avetisov*, Andrew Khomyakov, Elena Mozhevitina,
The nonstoichiometry phenomenon is well known for inorganic crystals. The crystal
nonstoichiometry results from general thermodynamic laws at T>0 K. But in the case of organic
crystals it has been thought the nonstoichiometry is not valid due to a molecule structure of organic
crystals.
In the research we have studied the crystals behavior of tris-(8-hydroxyquinoline)aluminum
(III) (Alq3) during powder heat treatment and crystal growth at controlled ligand 8hydroxyquinoline (8-Hq) vapor (P8-Hq). Alq3 is a known organic phosphor for OLED devices. The
scheme of Alq3 polymorphic transitions vs temperature has been established in [1,2].
We established the dependence of photoluminescence (PL) and crystal structure parameters of
β-Alq3 change vs P8-Hq at a fixed temperature. It has been shown that P8-Hq increase results to: a)
reduction of intensity at a fixed annealing (crystal growth) temperature; b) changing the
temperatures of polymorphic transitions and melting; c) hypsochromic shift of PL maximum from
517 to 504-508 nm (at Tann=580 K). All changes were reversible, indicating the thermodynamic
nature of the observed effects.
We explained the effects by the formation of a thermodynamically equilibrium crystal structure,
which depending on P8-Hq resulted to the change of Al atom number at a constant amount of ligands
in the crystal structure. The suggestion was proved by XRD analysis of the crystal lattice
parameters. We found the correlation between the cell volume vs P8-Hq, which indicated Alnonstoichiometry in Alq3 metal complex.
The research was financially supported by the Russian Science Foundation grant N 14-1301074.
References:
[1] M. Brinkmann et al. J. Am. Chem. Soc., 122 (21) (2000) 5147–5157
[2] R. I. Avetisov et al. Russian Microelectronics, 43(8) (2014) 526–530
S09-P13
Two-dimensional thermoluminescence method for checking crystals homogenity
B. Marczewska, P. Bilski, W. Gieszczyk, M. Kłosowski
Institute of Nuclear Physics PAN, ul. Radzikowskiego 152, 31-342 Kraków, Poland
e-mail:[email protected]
The inhomogeneous location of the impurity atoms or intentionally added activators occurs
naturally during a crystal growth. Thermoluminescence (TL), being one of the common
luminescence methods, is very sensitive to the presence of any impurity. In principle, in TL
materials the trapping centres, connected with dopants in the bulk matrix, act as memory cells for
radiation deposition events. Subsequent supply of thermal energy to the matrix leads to a release of
charge carriers trapped in these centers and their recombination with emission of light (TL). The TL
properties of the material are thus connected with the trap distribution in the bulk matrix structure
and trap activation, by the presence of dopants and/or by lattice defects. If in a TL reader a CCD
camera was used, a measurement of TL signal would give us an unique two-dimensional (2-D)
picture of TL signal distribution, and thereby the distribution of dopants.
The aim of the work is to study the possibility of the application of 2-D TL method for the
control of uniformity of the crystal related to dopant distribution in the volume of the bulk crystal.
The 2-D TL method will be presented on LiF crystals doped with Ti and Mg which were grown
at IFJ PAN in Kraków by Micro-Pulling Down (MPD) method in the form of thin rods and bulk
crystals obtained by Czochralski technique. The crystal rods of the diameter of about 2mm were cut
into small pieces, bulk crystals (with a diameter up to 20mm) were longitudinally and transversely
cut into slices of the thickness of 1mm. The surface of the slices were softly polished and rinsed.
Then the samples were irradiated in an uniform radiation Co-60 field to activate the color centers
connected with the dopants. Next the samples were read out in a 2-D TL reader constructed at IFJ
PAN. TL reader is equipped with a 60 mm diameter steel planchet heater, the temperature of which
can be raised linearly up to the temperature of 400°C with heating rates ranging with time over the
range from 1°Cs−1 to 10°Cs−1. The recording of the signal is realized by PCO SensiCamTM VGA
CCD 12-bit camera with registering of light signal with dynamic range up to 4500 counts per pixel.
The investigation revealed the lack of uniformity in the TL properties on the large surface of
LiF crystals up to a few cm2 which is connected with the non-uniform distribution of Ti and Mg
atoms. Although 2-D TL method cannot substitute more precise quantitative methods, it can
however be applied as an excellent tool for checking the homogeneity of crystals.
Acknowledgments: This work was supported by the National Science Centre (Contract No. DEC2012/05/B/ST5/00720).
S09-P14
Disorder control of nanostructural arrangement in AlGaN/GaN light-emitting
structures and related phenomena
A.E. Chernyakov1, M.E. Levinshtein2, М.М. Kulagina2, V.N. Petrov2, I.N. Smirnova2, S.I. Troshkov2 ,N.A.
Talnishnikh1, E.I. Shabunina*2, N.M. Shmidt2 , A.P. Kartashova2 , A.S. Usikov3, S.Yu. Kurin3 , H. Helava3 ,
Yu. Makarov3
1
Science and Technology Center of Microelectronics and Submicrometer Heterostructures, RAS, Polytekhnicheskaya
26, 194021, St. Petersburg, Russia
2
Ioffe Physical Technical Institute, Polytekhnicheskaya 26, 194021, St. Petersburg, Russia, [email protected]
3
Nitride Crystals, Inc. 181E Industry Ct., Ste. B, Deer Park, 11729, NY, USA.
The disorder of nanostructural arrangement (NA) in layers and light-emitting structures (LES)
based on III-nitrides is evoked by growth conditions, the lattice constants mismatch and tetrahedral
radiuses. Numerous forms of NA appear as different surface morphology of the structures grown.
As a result, the surface monitoring by means of atomic force microscopy (AFM) allows us to
determine NA disordering quantitatively by the AFM data processing using methods of multifractal
analysis [1,2]. The effectiveness of this approach to study the properties of GaN layers and highpower blue InGaN/GaN LEDs was shown earlier [1,2]. It is assumed to be an effective tool to find
out the reasons behind the low external quantum efficiency (~ 2%) and short lifetime (~ 2000 h) in
AlGaN/GaN LEDs. The quantitative evaluation of nanomaterial disorder in UV AlGaN/GaN LES
has not been assessed yet and its connection to the LED’s parameters has not been studied
previously.
In this work we present the first results of NA disordering characterization of multilayer
AlGaN/GaN light-emitting structures (360-365 nm) grown by hydride vapor phase epitaxy (HVPE)
on sapphire substrates. A variation of the buffer layer growth conditions allows one to grow 3 types
of structures with a different degree of disorder (p): 0.348, 0.370, and 0.390. The p values were
determined by the same way as [1,2]. The external quantum efficiency (η) was varied from 1.5% to
0.6% accordingly. The p values are higher than that in InGaN/GaN light-emitting structures (р<
0.345) having η higher than 40% but similar to those having low η values (less than 5%). It was
found out that for AlGaN/GaN LEDs an increase in р is accompanied by: 1) a rise in the direct and
reverse current at the low voltage (U < 3 V) and the conductivity of the leakage paths (shunts)
localized at extended defects such as V-defects [3] and stacking faults piercing p-n junction; 2) a
growth in the level of low-frequency noise spectral density (SI); 3) the appearance of local areas
with compositional instabilities in AlGaN reducing a local barrier height in LEDs; 4) increasing
crowding effect which might be revealed from the voltage fluctuations’ dependences SV on current.
These phenomena in AlGaN/GaN LEDs are more prominent than those in high quality InGaN/GaN
LEDs, but very similar to those in InGaN/GaN LEDs with high NA disordering (p > 0.350) and
low η values (less than 5%). The discussed effects may contribute into such phenomena as the
external quantum efficiency droop and reduced lifetime in AlGaN/GaN LEDs.
Acknowledgements
The work was supported by Russian Foundation for Basic Research (grants 14-02-31358 and 1402-00087) and Presidium of Russian Scientific Foundation (grant 9А32RAN)
References
[1] Shmidt N.M. et al., Nanotechnology, 12 (2001), 471.
[2] Chernyakov A.E. et al., Microelectronics Reliability, 52 (2012), 2180.
[3] Moseley Michael W. et al., Journal of Applied Physics, 117 (2015), 095301.
S09-P15
Effect of gamma irradiation on the optical properties of CVT grown ZnSe
single crystals P. Kannappan1,2, K. Asokan3, K. Baskar1, J. P. Leitao2, R. Dhanasekaran1*
1
Crystal Growth Centre, Anna University, Chennai-600 025, India
Department of Physics and I3N, University of Aveiro, 3810-193 Aveiro, Portugal
3
Inter University Accelerator Centre, New Delhi-110 067, India
*email: referring author email: [email protected]
2
ZnSe is an important material for detectors in the high energy radiation environments. This
semiconductor exhibit high radiation stability with high upper limit of working temperature. Hence
it is a very promising material for ‘scintillator photodiode’ detectors. In this work we present, the
effect of gamma irradiation on the optical properties of ZnSe. The ZnSe crystals were grown by
chemical vapour transport (CVT) method with iodine as a transporting agent using two zone
horizontal resistive heating furnace. During the growth, the temperature difference between the two
zones was maintained at 50˚C with the source temperature of 900˚C and the growth temperature of
850˚C. The growth period was about 15 days. The largest dimensions of 9×7×5 mm3 crystals were
obtained. Concerning the structural investigation, XRD analysis showed a cubic zinc-blend
crystalline phase. The composition of grown ZnSe crystal has been determined by EDXRF analysis
as Zn (52.5%) and Se (47.5%). The gamma-irradiation was performed using 60Co source with doses
in the range of 10 to 250 kGy at room temperature. The electronic energy levels structure of gamma
irradiated samples was studied by room temperature photoluminescence (PL) measurements. The
band edge emission at 439 nm (2.82 eV) is the dominant peak. In addition, the defect related peaks
were observed in the low energy side of the PL for both pristine and irradiated samples. The PL
peak shows a blue shift and increases in intensity with increase of gamma dose. The FT-Raman
study was performed in order to understand the lattice vibrations of gamma irradiated samples. All
these results will be discussed based on the dependence of gamma dose.
S09-P16
Thermal stability of ferroelectric domain gratings in Rb-doped KTP
Gustav Lingren1, Alexandra Peña*2,3, Andrius Zukauskas1, Charlotte Liljestrand1, Bertrand Ménaert2,3,
Benoît Boulanger2,3, Carlota Canalias1
1
Departement of Applied Phyisics, Royal Institute of Technology, Roslagstullsbacken 21, 10691 Stockholm (Sweden)
2
Univ. Grenoble Alpes, Inst NEEL, F-38042 Grenoble (France)
3
CNRS, Inst NEEL, F-38042 (France)
Rb-doped KTiOPO4 (RKTP) has proven to be one of the best materials for nonlinear optical
frequency conversion using quasi-phase matching (QPM). QPM is most commonly implemented
by periodically inverting the spontaneous polarization in ferroelectric crystals. The most-well
developed and reliable domain-engineering technique relies on electric field poling with finger
electrodes deposited by lithographic techniques [1]. However, state-of-the-art nonlinear optical
applications demand high aspect-ratio ferroelectric domain gratings, ranging from sub-µm
periodicities to large aperture crystals. Indeed, RKTP has demonstrated to be a promising candidate
for these types of applications [2, 3]. Nevertheless, variations in the coercive field due to
inhomogeneous stoichiometry over a single crystal wafer results in poor electric-field poling yield,
especially for thick crystals with short grating periods.
Recently, an alternative technique [4] for obtaining QPM devices has been successfully
demonstrated for KTiOPO4. In this method, a periodically poled (PP) crystal is used as a template
for epitaxial growth of high quality crystals, preserving the original domain structure of the seed,
opening up the possibility to grow large-aperture crystals with short periodicity. Thus, RKTP is an
excellent candidate for template growth: Not only does its orders of magnitude lower ionic
conductivity facilitate the template fabrication; it also shows superior resistance to optical damage
due to lower light-induced absorption in the blue-green spectral region [5], which, of course, will be
most beneficial for practical applications. Nevertheless, although the epitaxial growth of
periodically poled crystals is performed below the Curie temperature, the thermal stability of the
domain gratings at elevated temperatures becomes an issue of utmost importance.
In this work we study the stability of DWs in periodically poled RKTP at high temperatures.
We demonstrate that annealing the crystals above 550 °C induces DW motion. This motion is
highly anisotropic along the a- and b- crystallographic axes. Along the b-axis we observe tens of
micrometers domain contraction, whereas in a-direction the result is either orders of magnitude
lower DW motion or domain merging, depending on the initial domain configuration. Moreover, we
show that the DW stability depends on the period of the QPM device, leading to complete back
switching for sub-µm periods.
References:
[1] Yamada M., Nada N., Saitoh M., Watanabe K., Appl. Phys. Lett., 62 (1993) 435.
[2] Zukauskas A., Thilmann N., Pasiskevicius V., Laurell F., Canalias C., Opt. Mater. Express, 1 (2011)
201.
[3] Zukauskas A., Strömqvist G., Pasiskevicius V., Laurell F., Fokine M., Canalias C., Opt. Mater. Express,
1 (2011) 1319.
[4] Peña A., Ménaert B., Boulanger B., Laurell F., Canalias C., Pasiskevicius V., Segonds P., Félix C.,
Debray J., Pairis S., Opt. Mater. Express, 1 (2011) 185.
[5] Zukauskas A., Pasiskevicius V., Canalias C., Opt. Express, 21 (2013) 1395.
S09-P17
Argon ion irradiation effects on CdZnTe crystals: influence of the substrate temperature J.L. Plaza1, O. Martínez2, E. Repiso1, S. Rubio1 and E. Diéguez1
1
Laboratorio de Crecimiento de Cristales, Departamento de Física de Materiales, Facultad de Ciencias, Universidad
Autónoma de Madrid, Cantoblanco, 28049, Madrid (España)
2
GdS-Optronlab Group, Departamento Física Materia Condensada, Universidad de Valladolid, Edificio I+D, Paseo
de Belén 11, 47011 Valladolid, Spain
CdZnTe (CZT) crystals find interesting uses in a variety of detector-type applications. This
is due to its large absorption coefficient, high resistivity, high average atomic number and large
band gap [1]. The performance of CZT is affected by point defects, as well as structural and
compositional heterogeneities within the crystals, such as grain boundaries and Te inclusions. These
last kind of defects are created during the growth process and the cooling down phases [2] as a
result of the retrograde solid solubility of Te and a poor stoichiometric control [3]. The
concentration and distribution of Te inclusions within a device are one of the major contributions to
the degradation of CZT detectors.
Te precipitates on the surface can also increase the leakage current [4,5], thereby
deteriorating the device performance. Te inclusions and precipitates also act as traps for the charge
carriers, affecting to the charge collection efficiency as well as the energy resolution of the detector.
Our previous studies clearly revealed a pronounced effect when CZT surfaces were
irradiated with Ar ions at room temperature. Even for small fluences, a removal of polishing
scratches on the sample surfaces was observed. Correlated to this effect, an important enhancement
in the luminescence intensity of the irradiated samples was observed. Te inclusions also tend to
aggregate after the irradiation process and are also eliminated from the surfaces for the highest ion
fluences [6].
In this work the effect of the temperature of the sample in the range 300-600 K during Ion
Beam Sputtering of CZT crystals surfaces at different fluences is analised by means of Scanning
Electron Microscopy , Atomic Force Microscopy, Raman and Photoluminescence. It is
expected that increasing the temperature of CZT samples during the irradiation process will
enhance the beneficial effects this technique has shown when trying to reduce surface Te
inclussions and to increase the luminescence properties of CZT crystal surfaces.
References:
[1] H. Bensalah, J.L. Plaza, J. Crocco, Q. Zheng, V. Carcelen, A. Bensouici, E. Diéguez,
Appl. Surf. Sci. 257 (2011) 4633.
[2] P. Rudolph, Cryst. Res. Technol. 38 (2003) 542.
[3] Robert Triboulet, Paul Siffert, CdTe and Related Compounds; Physics, Defects,
Hetero- and Nano-structures, Crystal Growth, Surfaces and Applications
(European Materials Research Society Series), Institute of Leadership & Mana,
The Netherlands, 2010.
[4] T. Wang, W. Jie, D. Zeng, Mater. Sci. Eng. A 472 (2008) 227.
[5] H.Y. Pei, J.X. Fang, Phys. Status Solidi A 188 (2001) 1161.
[6] H. Bensalah, V. Hortelano, J.L. Plaza, O. Martínez , J. Crocco, Q. Zheng, V. Carcelen, E. Dieguez, J.
Alloys and Compounds 543 (2012) 233.
S09-P18
On Defects Detection in Crystals using Image Processing and Pattern
Recognition Tools
Moshe Porat
Computer Vision Laboratory
Department of Electrical Engineering
Technion
Haifa 32000 Israel
[email protected] and [email protected]
Most crystals contain small inclusions and imperfections. These defects interfere with the
passage of waves through the crystal and affect its reflections (e.g., X-Ray [1], visible light [2])
thereby help assessing its quality and the potential use of the crystal. Based on recent developments
in image processing and computer vision, in this work we introduce new tools for crystal
inspection. Understanding the defect type and other key features of a crystal can also be achieved
by applying pattern recognition technology.
We have tested tools of shape analysis, pattern matching, spectral analysis, image retrieval and
image registration. Localized descriptors have been used in this work to represent the crystal
normalized to cope with potential geometric transformations of the crystal due to various
viewpoints [3]. De-noising statistical tools have been applied to remove noise [4], and image
registration have been used to associate the same defects of the crystal from different directions.
The proposed tools and their performance are presented along with practical results based on actual
crystals. Our conclusion is that the proposed approach to crystal inspection using machine-vision
tools could be helpful in the task of crystals quality control and could improve presently available
inspection methods.
Figure 1. Defects detected using the proposed tools for the same crystal illuminated from various directions.
References:
[1] B. Raghothamachar, G. Dhanaraj, J. Bai and M. Dudley, "Defect Analysis in Crystals using
X‐ray Topography", Microscopy Research and Technique, Vol. 69 (2006), pp. 343-358.
[2] M. Porat, "An Image Processing Approach to Diamond Inspection and Evaluation", 24th
European Crystallographic Meeting (2007) Acta Cryst. A63 (2007) pp. s79.
[3] M. Porat and G. Shachor, "Signal Representation in the Combined Phase-spatial Space:
Reconstruction and Criteria for Uniqueness", IEEE Trans. on Signal Processing, Vol. 47 (1999), pp.
1701–1707.
[4] S. Nemirovsky and M. Porat, "Method and System for Processing an Image According to
Deterministic and Stochastic Fields", US patent 8,537,172 (2013).
S09-P22
Mystical source of electrically active chlorine at Cl doped CdTe
Lukáš Šedivý*,1, Jakub Čížek2, Eduard Belas1 and Roman Grill1
1
Institute of Physics, Charles University in Prague, Ke Karlovu 5, CZ-121 16, Prague 2, (Czech Republi)
2
Department of Low-Temperature Physics, Charles University in Prague, V Holešovičkách 2,
CZ-180 00, Prague 8, (Czech Republic)
CdTe/CdZnTe is an excellent material for manufacture of x-ray and gamma-ray room-temperature
detectors thanks to large linear attenuation coefficient, the possibility to make it high-resistive
CdTe/CdZnTe at room temperature, and satisfactory electron mobility and life-time. An
engineering of point defects existing in CdTe/CdZnTe crystals represent dominant task for routine
productions of detectors.
Annealing in well defined ambient component pressure, Cd or Te, is a standard procedure to
directly influence the density of native point defect, like cation and anion vacancies, cadmiun and
telurium interstitials, and their complexes with extrinsic impurities. Defects form energy levels in
band gap and affect resistivity and carrier life-time. Detailed understanding of the effect of
annealing to the point defect structure is crucial to get the optimal preparation method of
CdTe/CdZnTe radiation detectors.
Divalent acceptor Cd vacancy and its complexes with extrinsic substituting donors seated both in
cation and in anion sublattice are considered the most important for the defect self-compensation
and for preparation of high resistive material. In spite of the enormous effort in the past decades to
fix properties of Cd vacancies in CdTe/CdZnTe, namely formation and ionization energies and
large scatter of these quantities is found in the literature.
The high-temperature in situ galvanomagnetic measurements in classical Hall-bar six probe
configuration (HT-Hall) are used for observation of equilibrium concentration of native and
extrinsic point defects at high temperature.
Positron annihilation spectroscopy (PAS) are used for studiing of acceptor-type defects. Positron
trapping at defects change their annihilation characteristics and allows us to deduce the density of
the defects. Simultaneously, when PAS is done at various temperature, an information of charge
state of the defect may be estimated.
In this work we report on HT-Hall measurement in CdTe doped by chlorine or indium. The
relaxation of electrical conductivity and free carier concentration after step-like change of
surrounding Cd pressure was measured at high temperature and the chemical diffusion coefficient
was evaluated. The equilibrium concentration of native and extrinsic point defects was evaluated
from Hall effect measurement using theoretical model [1].
In parallel, PAS in as grown, Cd-annealed and Te-annealed Cl-doped CdTe , was done for native
and extrinsic point defects identification.
References:
[1] Grill R., Franc J., Höschl P., Turkevych I., Belas E., and Moravec P., IEEE Trans. Nucl. Sci. 52 (2005)
1925.
S09-P23
Structural examination of multilayer CrAlN/AlSiN films
Dimitrios Chaliampalias1,George Vourlias1, Eleni Pavlidou1, Nikolaos Vouroutzis1, Lilyana Kolaklieva2,
Roumen Kakanakov2, Vassiliy Chitanov2, Tetyana Cholakova2, Efstathios K. Polychroniadis*1
1
Aristotle University of Thessaloniki, Physics Department, University Campus, 54124, Thessaloniki (Greece)
2
Central Laboratory of Applied Physics, BAS, 61 St. Petersburg Blvd., 4000 Plovdiv (Bulgaria)
The deposition of transition metal nitrides on metallic components is a widely applied
technology for the modification of the surface properties of the materials. At the first stages the
deposition of binary nitrides was investigated, such as TiN, CrN and ZrN. This technology has
evolved by the deposition of ternary and quaternary nitrides. Latter progress on such films focuses
on the deposition of multilayer nitrides which were found to improve significantly the mechanical
properties and oxidation resistance. This happens because of the existence of many interfaces in the
film which have a double effect; they restrict the dislocation propagation because of the crack
dissipation when reaching those areas while the thermal stability is also improved as the increased
interfaces act negatively to the diffusion of ion species.
In the herein work the structure of multilayer CrAlN/AlSiN deposited by Cathodic Arc
Deposition is examined. The deposition was performed using a Platit π80+ unit by a cathodic arc
process equipped with a Lateral Arc Rotating Cathode (LARC) system. Firstly a bonding layer was
deposited which contained non-stoichiometric to stoichiometric CrNx compound followed by a
gradient nanocomposite Cr/Al/Si/N layer formed by manipulating the cathode current. After these
bonding layers nanocomposite AlSiN/SiN and CrAlN/SiN layers were successively deposited. The
latter process was repeated three times in order to create three repeating periods. The as formed
films were examined by Electron microscopy (SEM, TEM), X-ray diffraction (XRD) and X-ray
photoelectron spectroscopy (XPS).
The results showed that the as deposited coatings are composed of seven distinct layers with a
total thickness 9μm (Fig.1a). Though the stress created on the interfaces, no cracks or deformations
were observed in any area of the film. EDS analysis on several regions of the film revealed that the
light colored layers contain Cr while the dark ones not. The layer in contact with the substrate is the
bonding layer and contains higher Cr amounts. These observations are verified in the corresponding
line scanning image (fig. 1b) in which the variation of Cr is clearly illustrated. Moreover it is
revealed that in the Cr rich layers the Al concentration decreases. From XRD and XPS examination
it was found that on the surface the (Cr,Al)N solid solution is the predominant phase. XPS tracked
some minor oxides of Al and Cr which result from the high affinity of Al and Cr to low oxygen
amounts existing in the deposition chamber.
Fe
Cr
Si
Al
10μm
Cr
ri
ch
la
ye
r
Al B
ri on
ch di
la ng
ye la
r ye
r
substrate
Figure 1. Cross sectional SEM micrograph (a) and corresponding line scanning of the as deposited
films.
Acknowledgement: This work was supported from ΙKY Fellowships of excellence for postgraduate studies in Greece – Siemens Program
S09-P26
Dislocation mechanism of KDP growth from solution
H.V.Alexandru*1
1
Universuty of Bucharest, Faculty of Physics, Bucarest (Romania)
Macroscopic growth kinetic measurements of pyramidal faces of KDP crystal were performed
in dynamic regime. Three crystals were simultaneously grown in the same conditions, by
temperature decreasing method. Arrhenius corrections were made to 40°C growth temperature, for
our data and for some literature data; we have used to compare with. Surface diffusion mechanism
of growth appears as essential at small supersaturations, but several particular aspects dominate the
growth. Pyramidal faces are less sensitive to impurities and show a large dispersion of the growth
kinetic at σ ≈ 0.01-0.05. There are distinct BCF curves fitting the experimental data on several
ranges of supersaturations, corresponding to several efficiencies of growth. Bürgers vector and the
linear dimension of the dominant centers of dislocations involved during growth are discussed.
SESSION 10
Nanostructures & Nanoporous Crystals
Nucleation approach to polytypism in III-V nanowires
Jonas Johansson*1, Zeila Zanolli2,3, Kimberly A. Dick1,4
1
2
Solid State Physics, Lund University, Box 118, 22100, Lund (Sweden)
Peter Grünberg Institute & Institute for Advanced Simulation, Forschungszentrum Jülich, 52425 Jülich (Germany)
3
European Theoretical Spectroscopy Facility (ETSF)
4
Center for Analysis and Synthesis, Lund University, 22100, Lund (Sweden)
Several III-V nanowire materials systems exhibit features of polytypism, which is a kind of
polymorphism, where the polymorphs differ only in the layer stacking sequence. In bulk, all III-V
semiconductors, except nitrides, exhibit the zinc blende structure (3C polytype). However, when
these materials are grown as nanowires, they often exhibit a seemingly random crystal structure and
by tuning the growth parameters, more or less pure 3C or 2H can be fabricated. Sometimes often
higher order polytypes, such as 4H and 6H form. In order to use III-V nanowires in electronic and
optoelectronic applications, it is of highest importance to control and possibly also take advantage
of the polytypism.
In our current investigations, we take a classical nucleation approach to explain the
phenomenon of polytypism in metal particle-seeded III-V nanowires, including polytypes up to 6H.
In order to describe the formation of higher order polytypes, interaction between the stacked layers,
which goes beyond nearest neighbor interactions must be taken into account. For this purpose we
use the axial next nearest neighbor Ising (ANNNI) model [1]. In this model, the stacking sequence
is treated as a sequence of generalized spins and different sequences give different total energies,
depending on the interlayer interaction parameters. We will show how the total energies for several
polytypes can be calculated using ab initio techniques for any given material. In addition, from the
total energy expressions a phase diagram can be constructed, in which the ab initio results can be
visualized. Using this approach, it has been shown that 6H is the most stable SiC polytype and it
has been verified that the III-V semiconductors are very stable in 3C. Another, more kinetic
approach to the ANNNI modeling of polytypism is to keep track of the incremental energy change
due to the addition of single layers. This approach has been used to explain the preference of SiC to
grow in the 3C polytype during CVD.
In our approach to polytypism in nanowires, we use the ANNNI model to express the interface
energy between the forming nucleus and the underlying layers for the 3C, 6H, 4H, and 2H
polytypes. We will show how to combine this interface energy with our nucleation theoretical
framework and describe how we can use this model to calculate the formation probabilities of these
four polytypes as functions of supersaturation. Depending on the interaction parameters, the range
of attainable polytypes as a function of supersaturation can vary, and this can be graphically
represented. For this purpose we will introduce polytype attainability diagrams and discuss their
experimental relevance.
References:
[1] Selke W., Physics Reports, 170 (1988) 213.
[2] Johansson J., Bolinsson J., Ek M., Caroff P., Dick K. A., ACS Nano, 6 (2012) 6142.
InAs/GaAs SHARPLY-DEFINED AXIAL HETEROSTRUCTURES IN
SELF-ASSISTED NANOWIRES
D. Scarpellini1,2, C. Somaschini1, A. Fedorov3, S. Bietti1,*, C. Frigeri4,V. Grillo4,5, L. Esposito1, M. Salvalaglio1, A.
Marzegalli1, F. Montalenti1, E. Bonera1, P. G. Medaglia2 and S. Sanguinetti1
1
L–NESS and Dipartimento di Scienza dei Materiali, Università di Milano Bicocca, Milano, Italy,
2
Department of Industrial Engineering University of Rome Tor Vergata, Rome, Italy,
3
LNESS and CNR-IFN, Como, Italy,
4
CNR-IMEM Institute, Parma, Italy
5
CNR-S3-NANO Center, Modena, Italy
Semiconductor nanowires (NWs) are one of the most promising technologies for the development
of quantum devices such as single quantum dot emitters, single-electron transistors and tunnel
FET. Due to the reduced size of the interfaces, NWs can be used for the growth of highly
mismatched materials. However, the growth of the technologically relevant InAs/GaAs
interface in axial heterostructures with atomically sharp interfaces have never been achieved in
MBE self-assisted growth, thus hindering the use of this materials for the fabrication of several
devices.
In this presentation we show the procedure for the fabrication of axial, self-assisted, InAs/GaAs
NW heterostructures on silicon with atomically sharp interface, by decoupling the growth of
GaAs NW and InAs segment [1]. The lower GaAs segment is realized by growing self-assisted
GaAs NWs on Si (111) substrates, while the upper InAs segment is fabricated in a two-step
process by supplying In and As separately, resembling the droplet epitaxy procedure for the
fabrication of quantum dots [2].
Scanning transmission electron microscopy with High Angle Annular Dark Field detector
(HAADF, figure 1a) confirms the formation of InAs on the top of the GaAs NWs. High
resolution TEM (HR-TEM, point resolution 0.18 nm, figure 1b) demonstrates the formation of
an atomically sharp interface. The lattice parameters calculated by using the position of the
<111> spot in power spectra of HR-TEM (insets of figure 2b) are in agreement with the ones
of InAs and GaAs.
Figure 1. Panel (a): High resolution STEM-HAADF image of the InAs/GaAs NW tip. Panel (b): HR–TEM of the layer of
GaAs and the top InAs. The power spectra of InAs and zincblend GaAs are shown as insets
References:
[1] D. Scarpellini, C.Somaschini, A.Fedorov, S.Bietti,C.Frigeri, V.Grillo, L.Esposito, M.Salvalaglio,
A.Marzegalli, F.Montalenti, E.Bonera, P.G.Medaglia and S.Sanguinetti, Nano Letters (published
online) DOI: 10.1021/nl504690r
[2] N. Koguchi, K. Ishige, and S. Takahashi, J. Vac. Sci. & Technol. B 11, 787 (1993).
Mass-transport driven growth dynamics of AlGaAs shells deposited by
metalorganic vapor phase epitaxy around dense GaAs nanowire ensembles
Ilio Miccoli1, Paola Prete2, Nico Lovergine*1
1
Dip. di Ingegneria dell’Innovazione, Università del Salento, I-73100 Lecce, Italy
Istituto per la Microelettronica e Microsistemi, CNR, UOS Lecce, I-73100 Lecce, Italy
2
III-V compounds nanowires are expected to impact several device technology fields, ranging
from nanoelectronics, to nanophotonics, and photovoltaics, by offering both unprecedented
materials properties and novel device geometries/functionalities. Radial modulation of nanowire
composition and/or doping in the form of core-shell and core-multishell nanowire heterostructures
has been proposed for novel nano-LEDs/-lasers [1,2]. In order to exploit MOVPE technology for
the fabrication of such devices, good control over the growth process of radially-heterostructured
nanowires is necessary. While many efforts have been devoted in understanding/modelling the Aucatalysed (VLS) growth of III-V nanowires, much less is known on the growth dynamics of shell
materials by the conventional (Vapor-Solid) MOVPE around free-standing core nanowires.
We report on a detailed experimental analysis of AlGaAs shell growth by MOVPE around freestanding GaAs nanowires, the latter self-assembled by the Au-catalyzed process on (111)B-GaAs
wafers or GaAs/(111)Si hetero-substrates [3]. We demonstrate that the vapour mass-transport
supply of III-group species during shell growth couples with the nanowire size (e.g. their diameter)
and their local surface density on the substrate to determine the actual shell growth rate. A vapor
mass-transport model is proposed and validated, describing the MOVPE growth dynamics of the
shell material around dense ensembles of GaAs nanowires [4]. We predict a complex (non-linear)
dependence of the shell growth rate on initial GaAs nanowire diameters, heights, local densities on
the substrate, and deposition time (see Figure 1). Present results constitute a significant step towards
the controlled fabrication of core-shell and core-multishell nanowire heterostructures by MOVPE.
(a)
(b)
Figure 1: Average diameter of GaAs-AlGaAs core-shell nanowires as function of (a) their substrate
surface density (NW) after 10 min shell growth, and (b) the shell growth time for different NW.
References:
[1] B. Mayer, D. Rudolph, J. Schnell, S. Morkotter, J. Winnerl, J. Treu, K. Muller, G. Bracher, G.
Abstreiter, G. Koblmuller, Nat. Comm. 4 (2013) 2931.
[2] K. Tomioka, J. Motohisa, S. Hara, K. Hiruma, T. Fukui, Nano Lett. 10 (2010) 1639.
[3] I. Miccoli, P. Prete, F. Marzo, D. Cannoletta, N. Lovergine, Cryst. Res. Technol. 46 (2011) 795.
[4] I. Miccoli, P. Prete, N. Lovergine, submitted (2015).
Low Temperayure Growth of Porous ZnO Films
for Inorganic–Organic Hybrid Solar Cells
Kenji Yoshino1, 2, *, Akiko Mochihara1, 2, Kenji Kainou1, Minobu Kawano3, Yuhei Ogomi2, 3,
Qing Shen2, 4, Taro Toyoda2, 4, Shuzi Hayase2, 3
1
Department of Electrical and Electronic Engineering, University of Miyazaki,
1-1 Gakuen Kibanadai-nishi, Miyazaki 889-2192, Japan
2
CREST, Japan Science and Technology Agency (JST), 4-1-8 Honcho, Kawaguchi,
Saitama 332-0012, Japan.
3
Department of Engineering Science, Faculty of Informatics and Engineering,
The University of Electro-Communications, 1-5-1 Chofugaoka, Chofu,
Tokyo 182-8585, Japan.
4
Graduate School of Life Science and Systems Engineering, Kyushu Institute of
Technology, 2-4 Hibikino, Wakamatsu, Kitakyushu 808-0196, Japan
ZnO exhibits a wurtzite hexagonal structure and its direct optical bandgap of 3.4 eV at RT is
wide enough to transmit most of the useful solar radiation. In our previous work [1], non-doped
ZnO films were successfully grown on a polyethylene terephthalate film by a conventional spray
pyrolysis at 150 ˚C using a diethylzinc (DEZ)-based solution under an air atmosphere. It is well
known that the DEZ reacts with water and/or oxygen at low temperature, and ZnO can be
generated.
In this work, novel precursor solutions were prepared by the reaction of DEZ and water in some
solvent. Diethoxyethane and/or other ether solvents were used for the solution. In sample
preparation, all operations were carried out under inert gas (e.g. nitrogen). The hydrolysis reaction
was carried out by addition of water to DEZ in solvent under cooling condition to remove reaction
heat and avoid side reactions. After aging the reaction mixture at RT for 2 hours, the novel
precursor solution containing Zn-O structure compound was obtained.
A novel precursor for ZnO film deposition with Zn-O structure was synthesized by the reaction
of DEZ and water in some ether solvents. Non-doped ZnO films on a glass substrate have been
successfully grown by conventional spin coating using the novel precursor solution. Strong and
clear X-ray diffraction peaks of ZnO film grown by the novel precursor solution are observed
compared to those grown by simple DEZ solution. The samples have an optical transmittance of
more than 85%, and a porous surface determined from optical transmittance and scanning electron
microscopy (Fig.1), respectively. We also apply for perovskite based solar cell instead of TiO2.
o
TS=150 C
500nm
500nm
Fig.1 SEM images of the surfaces of non-doped ZnO/glass films using different solvent grown by
spin coating at 150 °C .
References:
[1] K. Yoshino, Y. Takemoto, M. Oshima, K. Toyota, K. Inaba, K. Haga, and K. Tokudome,
Jpn. J. Appl. Phys. 50 (2011) 040207.
Growth of ZnO nanostructures through rapid crystallization
Fioravanti Ambra*1,2, Bonanno Antonino2, Carotta Maria Cristina2,3, Sacerdoti Michele4
1
Dipartimento di Chimica, Università degli Studi di Parma, Parco Area delle Scienze 17A, 43124 Parma (Italy)
2
CNR-IMAMOTER, Via Canal Bianco 28, 44124 Ferrara (Italy)
3
CFR-Consorzio Futuro in Ricerca, Via Saragat 1/B, 44122 Ferrara (Italy)
4
Dipartimento di Fisica e Scienze della Terra, Università di Ferrara, Via Saragat 1/C, 44122 Ferrara (Italy)
ZnO is a II-VI compound semiconductor whose chemical bond is between covalent and ionic,
while the most stable phase is wurtzite-type structure belonging to the hexagonal space group
P63mc with the lattice parameters a = 3.2499 and c = 5.2066 Å.
The research focused on semiconductor ZnO already several decades ago. In recent years, the
renewed interest for ZnO has been aroused by the discovery of its aptitude for being grown in a
great diversity of nanostructures and of different functional properties. Indeed, ZnO can be grown
by a great deal of methods, such as vapour deposition, wet chemical methods, etc., obtaining the
widest family of unique nanostructures among all known materials. Novel applications resulted in
optoelectronics, hybrid solar cells, sensors, biomedical field.
The different nanostructures exhibit a large variety of morphologies such as nanoparticles,
nanowires, nanorods, nanosheets, nanoneedles, nanoflowers, etc.. They can be divided in one- (1D),
two- (2D) or three-dimensional (3D) structures depending on the number of dimensions in which
the material has nanometer modulations [1].
Wet chemical methods have been demonstrated to be a powerful and versatile technique for
growing ZnO nanostructures [2].
In this work, precipitation in alkaline water solution of zinc nitrate hexahydrate, using NH3·H2O
or HMTA (hexamethylenetetramine) as weak bases, was adopted for all synthesized materials.
Moreover the thermal treatments to obtain the crystallization were maintained under 100 °C.
XRD analysis showed that all powders exhibited hexagonal wurtzite-type structure.
Among the obtained morphologies, here we describe four of them: two constituted by elongated
crystals (2D structures), forming flower-like nanostructures (Fig. 1a) or nanoneedles (Fig. 1b). In
the first case the elongated nanocrystals (in the [0001] direction) are hexagonal prisms that are
connected at a central point, where a probable twinning from the (000 ) plane occurred. In the
second one, the elongated crystals ended on an hexagonal base pyramid. The second two
morphologies (3D structures) can be described as nanoparticles, agglomerated in different shapes:
bi-pyramidal (Fig. 1c) or nanoflowers (Fig. 1d). For the last material, X Ray diffraction analysis
suggests a probable formation of crystallites oriented as the (0001) basal plane.
Figure 1 a,b,c,d. SEM images of flower-like nanostructures, nanoneedles, bi-pyramids and nanoflowers).
References:
[1] C. Suryanarayana, C.C. Koch, Hyperfine Interact. 130 (2000) 5–44.
[2] Sheng Xu, Zhong Lin Wang, Nanoresearch 11( 2011) 1013-1098.
Heat of Fusion of Nano Crystals
Clain Alexander E., Novins Caleb A. and Amanuel Samuel*
Department of Physics and Astronomy, Union College, 807 Union Street, Schenectady, NY 12308 (USA)
In order to control the size of 2-decanol nano crystals, we physically confined 2-decanol in nano
porous silica. Heat of fusion and melting temperatures of the physically confined systems were
studies using a power compensated Differential Scanning Calorimeter, DSC. Our results revealed
that the melting temperature decreased as the physical size of the materials decreased and a linear
relationship is observed between the melting temperature and the inverse of size. This is in
agreement with previous experimental observations and qualitative prediction from the GibbsThompson equation.[1-5] The equation, however, assumes that the heat of fusion to be independent
of physical size. Our results, on the other had, revealed reduction in the apparent heat of fusion as
the physical size decreases. This seeming contradiction can be explained if there were interfacial
layer/s of molecules that would not go under phase transition and do not contribute to the energy of
transition (heat). The correct heat of fusion should be determined from normalizing the apparent
heat by the mass of the material that actually undergoes phase transition and not the total mass. It is
difficult, however, to determine the mass of the materials that actually undergoes phase transition
from experimental measurements or directly. In a complementary approach, we have previously
used a simple geometrical model to estimate the thickness of the non-freezing interfacial layers and
estimated the density of the non-freezing layers.[6,7] In this paper, we present our studies how we
were able to incorporate the interfacial molecules in the crystallization of secondary alcohols and
how this has influenced the apparent heat of fusion.
References:
[1] Alba-Simionesco C., Coasne B., Dosseh G., Dudziak G., Gubbins K. E., Radhakrishnan R., Sliwinska
Bartkowiak M., J. Phys. Condens. Matter, 18 (2006) R15–R68.
[2] Alcoutlabi M., McKenna G. B., J. Phys. Condens. Matter, 17 (2005) R461–R524.
[3] Christenson H., J. Phys. Condens. Matter, 13 (2001) R95–R133.
[4] Hamilton B. D., Ha J., Hillmyer M. A., Ward, M. D., Acc. Chem. Res. 45 (2012) 414.
[5] Huber P., J. Phys. Condens. Matter 27 (2015) 103102.
[6] Amanuel S., Bauer H., Bonventre P., Lasher D., J. Phys. Chem. C 113 (2009) 18983–18986.
[7] Bauer H. C., Safiq A. D., Dulmaa J., Khraisat A. S., Amanuel S., MRS Proc. 1423 (2012) mrsf11–
mrsf1423 – rr06–04.
Filamentary growth of metals
Gunther Richter
Max Planck Institute for Intelligent Systems, Stuttgart, Germany
One dimensional nanostructures have the prospect to change the properties of materials used in contemporary devices. Physical properties change with dimension and size. Ceramics, semiconductor and carbon materials are easily synthesized as one dimensional structures with typical diameters of several nanometers and length‐diameter ratios of 1000:1. However, only the metals as one of the oldest are difficult to fabricate in similar geometries. In contrast, micrometer diameter, millimeter length macroscopic metallic nanowires were grown and reported decades ago via the reduction of metal halides, based on a process described already in 1574. Recently we developed a process to grow perfect defect and flaw free nanostructures with diameters of several ten nanometers, attached on substrates. The initiator mediated filamentary crystal growth process is based on the physical vapour deposition technique. Metals with face centred (Cu, Ag, Au, Pd) crystal structure were synthesized successfully with the new technique. Typical diameters of the nanowhiskers are 100 nm and lengths of up to 200 µm are observed, giving aspect ratios of up to 2000:1. Microstructure characterization of the nanowires was carried out predominantly by electron microscopy, revealing a perfect, flaw and defect free bulk and surface crystal structure. No dislocations, stacking faults, or grain boundaries were detected. The growth direction is generally along the <110> crystallographic direction of the face centered cubic lattice. The nanowire surface is formed by low indexed crystallographic planes, the {111} and {100}. The overall geometry is dominated by the minimization in terms of surface energy and resembles the Wulff shape. It was not possible to detect impurities from the growth process on the surface or in the bulk of the nanowires. Preliminary tensile and bending test were performed to study the mechanical properties. The nanowires show flow and yield stresses close to the theoretical limits. Traditional theories attribute the growth of whiskers with the presence of a screw‐dislocation. However, extensive microstructure studies by transmission electronmicroscopy (TEM) in NWs did not reveal any indication that screw dislocations are present in metal NWs. But our work revealed that NWs grow only on substrates where small areas with high surface energies are surrounded by areas with low surface energies. Diffusion of adatoms toward the small high energy areas leads to nucleation and eventually to NW growth. Fig. 1: Micrographs of Cu NWs: (a) SEM; (b) Dark-field TEM; (c) HRTEM
A comparative numerical analysis of circular and rectangular well
nanopatterning on c-plane sapphire substrates for selective area growth of AlN
islands
I. Davis Jacob, A. Rosy, G.K.Priya Merline and M.Chitra*
*email for correspondence : [email protected], [email protected]
Abstract: A comparative numerical analysis of circular nanopatterning and rectangular
nanopatterning has been performed on c-plane sapphire interfaces for selective area growth of AlN
islands. This is to reduce the threading dislocations on the GaN epitaxial layers arising due to lattice
mismatch between GaN and sapphire. The dislocation density on the GaN epitaxial layers growing
on the substrate is expected to decrease when the linear periodicity of the nanopatterning agrees
with certain ratios of alternating sapphire and aluminium nitride lattices. Numerical analysis on the
one-to-one mapping of the number of unit cells in a given area of c-cut GaN interface with the unit
cells on the c-plane substrate comprising of sapphire and aluminium nitride gives rise to two area
domains of sapphire which are marked by matched and mismatched boundaries. Sapphire can be
patterned or etched periodically in the shape of circular nanowells on the c-plane surface for
selective area growth of AlN. The periodicity, patterning density and sizes (diameter) of the
aluminium nitride islands were estimated. In addition, the extent of matched sapphire area and the
boundary of the mismatched area are calculated. The same parameters are calculated for rectangular
nanowells and compared.
Dual-Type Compound Semiconductor Nanowire Arrays
Joona-Pekko Kakko1, Farid Bayramov2,3, Bakhysh Bairamov2, Tuomas Haggrén1, Veer Dhaka1, Teppo
Huhtio1, Antti Peltonen4, Hua Jiang5, Esko Kauppinen5, and Harri Lipsanen1
1
Aalto University, Department of Micro and Nanosciences, P.O. Box 13500, FIN-00076
Aalto, (Finland)
2
Ioffe Physical-Technical Institute RAS, 194021, 26 Polytekhnicheskaya ul., St. Petersburg, (Russia)
3
St. Petersburg Academic University – Nanotechnology Research and Education Center, Russian
Academy of Sciences, St. Petersburg, 194021 (Russia)
4
Aalto-Nanofab, Micronova, Aalto University, P.O. Box 13500, FI-00076 Aalto, (Finland)
5
Department of Applied Physics and Nanomicroscopy Center, Aalto University, P.O. Box 15100, FI00076 Aalto, (Finland)
Dual-type nanowire (NW) array is a novel structure, where two types of NWs – with
selective-area epitaxy (SAE) and via vapour-liquid-solid (VLS) – are grown side-by-side on a
common substrate using metalorganic vapour phase epitaxy (MOVPE). Figure 1 presents the most
important steps to fabricate a dual-type array and a false-color SEM image of the structure. In this
work, we present the fabrication scheme of the dual-type NW array and present the properties of the
novel structure; complex configurations, compositional control, micro-Raman spectroscopy and
micro-photoluminescence measurements that reveal the crystalline quality and precautions to avoid
the parasitic growth, due to the two subsequent growth steps.
Compositional control and complex configurations can be achieved by using different
precursor materials or varying growth conditions in the two growth steps. Complex configurations
increase light trapping of the structure and compositional contrast introduces an additional band
gap, which in turn could widen the absorption spectrum. These qualities are beneficial, for example,
in a solar cell application.
Figure 1. Schematic illustration of the fabrication steps for dual-type NW arrays and a
SEM image of final GaAs/GaAs dual-type array.
References:
[1] Joona-Pekko P. Kakko, Tuomas Haggrén, Veer Dhaka, Teppo Huhtio, Antti Peltonen, Hua Jiang, Esko
Kauppinen, and Harri Lipsanen, Nano Letters, 15 (2015) 1679–1683.
chitra: A comparative numerical
POSTER
S10-P01
Vapour phase catalyst-free growth of β-Ga2O3 nanowires
Davide Calestani*1, Alabi Aderemi Babatunde2, Nicola Coppedè1, Marco Villani1, Laura Lazzarini1, Filippo
Fabbri1, Giancarlo Salviati1, Roberto Fornari3, Andrea Zappettini1
1
IMEM-CNR, Parco Area delle Scienze 37/A, Parma (Italy)
Department of Physics, University of Ilorin, Ilorin (Nigeria)
3
Dept. of Physics and Earth Sciences, University of Parma, Parco Area delle Scienze, 7/A, Parma (Italy)
2
Gallium oxide can be classified as a transparent conducting oxide (TCO) with the widest
transparency range (band gap energy is about 4.9eV), high chemical stability, n-type conductivity,
and strong blue photoluminescence (PL). It crystallizes in five known crystalline modifications (α,
β, γ, δ and ε phases), among which β-Ga2O3 is the most stable polymorph. The β-phase Ga2O3 is
characterized by a monoclinic crystal structure with two distinct gallium sites (six-and fourcoordinated) and three oxygen sites (three- and four-coordinated). Native point defects are known to
form readily in this complex oxide lattice and are responsible for a range of important physical
properties. Specifically, oxygen vacancies have been proposed to lead to the formation of shallow
donor states which are considered to be the source of n-type electrical conductivity.
In recent years, low-dimensional β-Ga2O3 structures including NWs, nanobelts, nanorods and
nanosheets have attracted growing attention of researchers due to their superior properties as
compared to their bulk counterpart. One very important advantage of β-Ga2O3 NWs is their large
surface to volume ratio providing more surface states to interact with the surroundings. The strong
blue light emission property of the Ga2O3 nanobelts also suggests them as new candidates for
fabricating functional optoelectronic nanodevices and nanosize sensors.
In this work we report the successful synthesis of β-Ga2O3 nanowires/nanobelts using simple a
physical evaporation technique, derived from previous experiments on the vapour phase growth of
metal oxide nanostructures from a simple metal source. Nanostructures have been grown on
different kind of substrates (silicon, alumina, sapphire) starting from metallic Ga source that, in the
proper alternation of argon and argon-oxygen mixture atmospheres, evaporates, deposits and finally
feeds the growing nanocrystals by reaction with oxygen in the proper temperature range.
No catalyst have been used to force the nucleation of nanowires and no metal-organic precursor
have been used, so that only high purity β-Ga2O3 nanostructures can be obtained. As a case of
study, nanowires have been grown also on Au and Pt films for comparison.
The morphological, structural and optical properties of the obtained nanostructures have been
characterized, revealing thin (mainly ranging from 5 to 20 nm) and long (up to tens of micrometers)
nanowire- or nanobelt-shaped crystals. Their properties have been studied by means of SEM and
TEM microscopy as well as cathodoluminescence, mainly comparing results obtained for different
growth conditions and substrates.
Figure 1. SEM image of β-Ga2O3 nanowires and nanobelts obtained on alumina substrate
S10-P03
Bioceramic Coatings Produced on Commercially Pure Titanium by the
Induction Heat Treatment and Nanostructure Surface Modification
Fomin Aleksandr*1, Fomina Marina1, Rodionov Igor1, Koshuro Vladimir1, Poshivalova Elena1,
Zakharevich Andrey2, Skaptsov Aleksandr2, Atkin Vsevolod2
1
2
Yuri Gagarin State Technical University of Saratov, 410054, Politekhnicheskaya, 77, Saratov, (Russia)
Saratov State University named after N.G. Chernyshevsky, 410012, Astrakhanskaya, 83, Saratov, (Russia)
In medical practice commercially pure titanium and medical titanium alloys are widely used
when joint endoprostheses and dental implants are fabricated. It is especially important to produce
biocompatible materials and coatings that improve osseointegration [1]. The implant coatings
should have high morphological heterogeneity of the micro- and nanostructure [2]. The surface
modification is usually performed by plasma spraying, oxidation, etc. A characteristic feature of
these methods is high energy consumption, complex technological sequence, decreased mechanical
strength together with high porosity, relatively long duration in order to obtain the required phasestructural state.
The surface of the titanium samples was oxidized using induction heat treatment (IHT). As a
result of IHT the oxide coatings of titania (TiO2) were formed. The next step included colloidal
modification with hydroxyapatite (HAp) nanoparticles. The IHT effect in the temperature range of
600...1200 °C on the performance of structure and properties of the coatings was determined.
Titania coating production included the formation of dotted, needle-like, plate, and prismatic
crystals (Fig.1a). Oxide coatings were modified with HAp nanoparticles (Fig.1b,c). Increased
cellular activity and accelerated osseointegration on the surface of implants with nanocrystalline
coatings were observed [2].
Figure 1. Morphology of coatings: a – TiO2 coating; b,c – TiO2 + HAp coating
The research was carried out with financial support of grant RFBR 13-03-00898 “a”,
scholarship SP-617.2015.4, and project 1189 in the framework of the basic part of the state
educational task for institutions of higher education, under the jurisdiction of the Ministry of
Education of the Russian Federation in the field of scientific activity.
References:
[1] Dorozhkin S.V., Biomaterials, 31 (2010) 1465-1485.
[2] Fomin A.A., Rodionov I.V., Steinhauer A.B., et al., Proc. of SPIE, 9031 (2014) 90310H.
S10-P04
Metal-Oxide Coatings with Ultrafine Crystalline Structure on Medical Implants
Fabricated from Stainless Steel
Rodionov Igor*, Fomin Aleksandr, Fomina Marina, Poshivalova Elena, Koshuro Vladimir
1
Yuri Gagarin State Technical University of Saratov, 410054, Politekhnicheskaya, 77, Saratov, (Russia)
The structure of metal-oxide coatings produced on stainless steel 12Cr18Ni9Ti by thermal
modification in the air was studied using scanning electron microscopy (SEM) [1,2]. The influence
of heat treatment of medical implants during osteosynthesis on the changes in the morphological
parameters of coatings, their dimensional structural characteristics was determined. In the course of
SEM studies it was determined that during thermal modification of the surface of steel substrates in
the air polycrystalline metal-oxide films with ultrafine structure were formed (Fig.1a). Under the
studied conditions at the temperatures of 350 and 400 °C and oxidation duration of 1.5 hours the
production of both bulk and surface structure of coatings was characterized by the formation of
numerous nucleations and growth of oxide particles (Fig.1b). The coatings acquired mainly fine
structure, the specific feature of which was increased porosity and microheterogeneity.
Based on the studies of the characteristics of heterogeneous oxide coatings produced on
substrates of medical stainless steel by gas-thermal oxidation it was found that the resulting thin
coatings have the ability to ingrow into the bone (Fig.1c). The application of the developed coatings
under osseointegration of steel orthopedic implants into different bone segments is explained.
Figure 1. Micro- (a) and nanostructure (b) of an oxide coating and the intraosseous part of an oxidized implant with
bone fragments after in vivo testing (c)
The research was carried out with financial support of project 1189 in the framework of the
basic part of the state educational task for institutions of higher education under the jurisdiction of
the Ministry of Education of the Russian Federation in the field of scientific activity, grant of the
President of the Russian Federation MD-3156.2015.8 and grant RFBR 13-03-00248 “a”.
References:
[1] Rodionov I.V., Inorganic Materials: Applied Research, 4(2) (2013) 119-126.
[2] Rodionov I.V., Metal Science and Heat Treatment, 55 (2014) 599-602.
S10-P07
Low Temperature Growth of Ga-doped ZnO Thin Films
Grown by Atmospheric Spray Pyrolysis for CuInGaSe2 Based Solar Cells
Kenji Yoshino1,*, Akiko Mochihara1, Himeka Tominaga1, Youei yamaga1, Takashi Minemoto2, Shigeru Ikeda3
1
1-1Gakuen Kibanadai-nishi, Miyazaki 889-2192, Japan.
2
Department of 1Department of Electrical and Electronic Engineering, Ritsumeikan University, Kusatsu, Japan
3
Research Center for Solar Energy Chemistry, Osaka University, Osaka, Japan
Transparent conductive oxide (TCO) materials have attracted much attention for use in liquid
crystal displays and photovoltaic devices. In particular, Sn-doped In2O3 (ITO) is known as a good
transparent conductive oxide material. Recently, ZnO has also been studied as a TCO material
because material (Zn) cost is very low in comparison to that of ITO (In). ZnO has shown promise
for many applications including gas sensors, transport electrodes, piezoelectric devices, varistors
and surface acoustic wave devices. Its direct optical band gap of 3.4 eV at room temperature is wide
enough to transmit most of the useful solar radiation in ZnO/CuInSe2 based solar cells.
Furthermore, ZnO is a good candidate to substitute for ITO (In-doped In2O3) and FTO (F-doped
SnO2) in transparent conductive electrodes. Many techniques have been employed to produce the
ZnO thin films including molecular beam epitaxy, metal organic chemical vapour deposition, radio
frequency magnetron sputtering, spray pyrolysis and sol-gel methods.
In our previous work [1, 2], undoped ZnO films on glass substrates were grown by a spray
pyrolysis method at low temperature (RT ~ 300 ˚C). Polycrystalline ZnO thin films were
successfully grown at 100 °C under an air atmosphere. Diethylzinc (DEZ) was used as the Zn
source material. The DEZ solution was diluted by some solvent in order to use safely under an air
atmosphere. X-ray diffraction indicates that (10-10) and (10-11) peaks are dominant. The lattice
constants of the a and c axes are larger than those of ICDD data. The samples have c-axis (0002)
orientation with increasing substrate temperature. Furthermore, the lattice constants of the a and c
axes become closer to those of ICDD data with increasing substrate temperature.
In this work, growth of Ga-doped ZnO (GZO) /glass films using DEZ solution was carried out
by spray pyrolysis at 150°C. The average transmittance of undoped and GZO films showed 80%.
The sheet resistivity of Ga-doped ZnO decreased to 30 /sq. by UV irradiation for 60 min. The
sprayed GZO films were examined as TCO layer for Cu(In,Ga)Se2 (CIGS) solar cells. After
covering clean soda-lime glass (SLG) substrates with back electrodes of Mo films (0.8 μm) by
sputtering, CIGS films (2 μm) were deposited using physical vapor deposition. Buffer layers of CdS
films (≈ 50 nm) were prepared by chemical bath deposition. Buffer layers of ZnO films (≈ 80 nm)
were also prepared by RF sputtering method [3]. The GZO films were successfully grown on
ZnO/CdS/CIGS/Mo/glass by atmospheric spray pyrolysis using DEZ based solution. The efficiency
of the obtained device was 10.3%. This result shows the sprayed low resistivity GZO films will be
one of the promising candidates for non-vacuum fabricated TCO layer of CIGS solar cell.
References:
[1] K. Yoshino, Y. Takemoto, M. Oshima, K. Toyota, K. Inaba, K. Haga, K. Tokudome,
Jpn. J. Appl. Phys. 50 (2011) 040207.
[2] K. Yoshino, M. Shinmiya, N. Kamiya, J. Kosaka, M. Oshima, Y. Takemoto, K. Toyota,
K. Inaba, K. Haga, K.Tokudome, Jpn. J. Appl. Phys. 50 (2011) 108001.
[3] T. Minemoto, Y. Hashimoto, T. Satoh, W. S. Kolahi, T. Negami, H. Takakura, Y. Hamakawa.,
Sol. Energy Mater. Sol. Cells, 75 (2003) 121.
S10-P08
Low Temperature Growth of Ga-doped ZnO Thin Films
Grown by Atmospheric Spray Pyrolysis for CuInGaSe2 Based Solar Cells
Kenji Yoshino1,*, Akiko Mochihara1, Himeka Tominaga1, Youei yamaga1, Takashi Minemoto2, Shigeru Ikeda3
1
1-1Gakuen Kibanadai-nishi, Miyazaki 889-2192, Japan.
2
Department of 1Department of Electrical and Electronic Engineering, Ritsumeikan University, Kusatsu, Japan
3
Research Center for Solar Energy Chemistry, Osaka University, Osaka, Japan
Transparent conductive oxide (TCO) materials have attracted much attention for use in liquid
crystal displays and photovoltaic devices. In particular, Sn-doped In2O3 (ITO) is known as a good
transparent conductive oxide material. Recently, ZnO has also been studied as a TCO material
because material (Zn) cost is very low in comparison to that of ITO (In). ZnO has shown promise
for many applications including gas sensors, transport electrodes, piezoelectric devices, varistors
and surface acoustic wave devices. Its direct optical band gap of 3.4 eV at room temperature is wide
enough to transmit most of the useful solar radiation in ZnO/CuInSe2 based solar cells.
Furthermore, ZnO is a good candidate to substitute for ITO (In-doped In2O3) and FTO (F-doped
SnO2) in transparent conductive electrodes. Many techniques have been employed to produce the
ZnO thin films including molecular beam epitaxy, metal organic chemical vapour deposition, radio
frequency magnetron sputtering, spray pyrolysis and sol-gel methods.
In our previous work [1, 2], undoped ZnO films on glass substrates were grown by a spray
pyrolysis method at low temperature (RT ~ 300 ˚C). Polycrystalline ZnO thin films were
successfully grown at 100 °C under an air atmosphere. Diethylzinc (DEZ) was used as the Zn
source material. The DEZ solution was diluted by some solvent in order to use safely under an air
atmosphere. X-ray diffraction indicates that (10-10) and (10-11) peaks are dominant. The lattice
constants of the a and c axes are larger than those of ICDD data. The samples have c-axis (0002)
orientation with increasing substrate temperature. Furthermore, the lattice constants of the a and c
axes become closer to those of ICDD data with increasing substrate temperature.
In this work, growth of Ga-doped ZnO (GZO) /glass films using DEZ solution was carried out
by spray pyrolysis at 150°C. The average transmittance of undoped and GZO films showed 80%.
The sheet resistivity of Ga-doped ZnO decreased to 30 /sq. by UV irradiation for 60 min. The
sprayed GZO films were examined as TCO layer for Cu(In,Ga)Se2 (CIGS) solar cells. After
covering clean soda-lime glass (SLG) substrates with back electrodes of Mo films (0.8 μm) by
sputtering, CIGS films (2 μm) were deposited using physical vapor deposition. Buffer layers of CdS
films (≈ 50 nm) were prepared by chemical bath deposition. Buffer layers of ZnO films (≈ 80 nm)
were also prepared by RF sputtering method [3]. The GZO films were successfully grown on
ZnO/CdS/CIGS/Mo/glass by atmospheric spray pyrolysis using DEZ based solution. The efficiency
of the obtained device was 10.3%. This result shows the sprayed low resistivity GZO films will be
one of the promising candidates for non-vacuum fabricated TCO layer of CIGS solar cell.
References:
[1] K. Yoshino, Y. Takemoto, M. Oshima, K. Toyota, K. Inaba, K. Haga, K. Tokudome,
Jpn. J. Appl. Phys. 50 (2011) 040207.
[2] K. Yoshino, M. Shinmiya, N. Kamiya, J. Kosaka, M. Oshima, Y. Takemoto, K. Toyota,
K. Inaba, K. Haga, K.Tokudome, Jpn. J. Appl. Phys. 50 (2011) 108001.
[3] T. Minemoto, Y. Hashimoto, T. Satoh, W. S. Kolahi, T. Negami, H. Takakura, Y. Hamakawa.,
Sol. Energy Mater. Sol. Cells, 75 (2003) 121.
S10-P10
Nitride-based self-assembled magnetic nanocrystals and complexes
Giulia Capuzzo 1, Thibaut Devillers 1, Andrea Navarro-Quezada1, Mauro Rovezzi2, Tomasz Dietl3, Maciej
Sawicki3, and A.Bonanni*1
1
Institut für Halbleiter-und-Festkörperphysik, Johannes Kepler University, Altenbergerstrasse 69, A-4040 Linz
(Austria)
2
European Synchrotron Radiation Facility, 6 rue Jules Horowitz, F-38043 Grenoble (France)
3
Institute of Physics, Polish Academy of Sciences, al. Lotników 32/46, PL-02-668 Warszawa (Poland)
Gallium nitride (GaN) and related alloys as building-blocks for state-of-the-art light emitting
diodes and high-power devices have risen to the position of technologically most significant
semiconductors next to Silicon. Through the addition of magnetic dopants fostering the formation
of active magnetic complexes or driving the system to the state of a condensed magnetic
semiconductor, these materials are expected to open striking views in both fundamental and
application-oriented research.
We summarize our recent work on the fabrication by metalorganic vapor phase epitaxy of
magnetic nitrides and highlight how – by exploiting in particular synchrotron radiation and
microscopy techniques – we have correlated the growth parameters and protocols to the structural,
magnetics, optical properties of the epitaxial layers. We give an overview on how we have
unraveled and we can now control by fabrication parameters and co-doping a number of nonanticipated features of these systems, like the self-aggregation and performance of functional
magnetic nanocrystals FexN [1-7] and magnetooptically active complexes Mn-Mgk [8,9] embedded
in GaN.
The work was supported by the European Reasearch Council (ERC, Project 227690) and by the
Austrian Science Foundation (FWF, projects #22477, #24471, #26830).
References:
[1] A. Bonanni et al., Phys. Rev. Lett. 101, 135502 (2008).
[2]M. Rovezzi et al., Phys. Rev. B 79 , 195209 (2009).
[3] A. Navarro-Quezada et al., Phys. Rev. B 81 , 205206 (2010).
[4] A. Navarro-Quezada et al., Phys. Rev. B 84 , 155321 (2011).
[5] I. A. Kowalik et al., Phys. Rev. B 85 , 184411 (2012).
[6] A. Grois et al., Nanotechnology 25 , 395704 (2014).
[7] A. Bonanni and T. Dietl, Chem. Soc. Rev. 39, 528 (2010).
[8] T.Devillers et al., Scientific Reports 2, 722 (2012).
[9] T.Devillers et al., APPL: Phys: Lett. 103, 211909 (2013).
[10] T.Devillers et al., Cryst. Growth. Des 15, 587 (2015).
S10-P11
Growth and Formation of Nanostructures on Metal Surfaces under the Action
of Nanosecond Laser Pulses
Mikolutskiy Sergey*, Khasaya Radmir, Khomich Yuri, Yamshchikov Vladimir, Zheleznov Yuri
Institute for Electrophysics and Electric Power RAS, 18, Dvortsovaya nab., 191186 St.-Petersburg (Russia)
The paper describes the mechanism of nanostructure formation on the metal surface by
nanosecond laser radiation. In our work we use one laser beam without any optional devices and
masks. Such method is called the direct laser nanostructuring [1,2]. The analysis of irradiated
surfaces is carried out by an atomic-force microscope (AFM). AFM-analysis shows that the
formation of surface nanostructure occurs in peripheral low intense part of irradiation zone where
only a surface melting is observed. For example, figure 1 represents nanostructures obtained on
titanium and nickel surfaces as a result of multipulse irradiation by ArF-laser.
In order to explain the nanostructure occurrence we offer the theoretical model of nanostructure
formation on solid surface by nanosecond laser pulses melting the material [3]. The problem can be
divided on two parts. In the first part we consider the process of material melting occurring as a
result of laser impact and the Stefan problem with the corresponding boundary conditions is solved.
In the second part we consider the process of a melted layer cooling at the expense of heat
transmission into the solid phase in combination with a nucleation theory explaining the formation
of crystalline seeds. As a result, we obtain the expression for the characteristic size of
nanostructures depending on the pulse duration and energy.
(a)
(b)
Figure 1. AFM images of titanium (a) and nickel (b) surfaces irradiated by ArF-laser
References:
[1] Tokarev V.N., Khomich V.Yu., Shmakov V.A., Yamshchikov V.A., Doklady Physics, 53 (2008) 206.
[2] Ganin D.V., Mikolutskiy S.I., Tokarev V.N., Khomich V.Yu., Shmakov V.A., Yamshchikov V.A.,
Quantum Electronics, 44 (2014) 317.
[3] Mikolutskiy S.I., Khomich V.Yu., Shmakov V.A., Yamshchikov V.A., Nanotechnologies in Russia, 6
(2011) 733.
S10-P13
The influence of V/III flow ratio on the self-induced InAs nanowires growth
Nickolay V. Sibirev, Umesh Prasad Gomes, Daniele Ercolani, Mauro Gemmi, Vladimir G. Dubrovskii, Fabio Beltram, and Lucia
Sorba
Nanowires (NWs) of III–V semiconductor compounds are promising building blocks for future
nanophotonic and nanoelectronic devices and functional photonic circuits. III–V NWs are usually fabricated by
various epitaxy techniques via the so-called vapor–liquid–solid mechanism activated by a metal (usually Au)
catalyst. Yet, so far catalyst contamination in CMOS technology remains to be challenging. Recently several
groups demonstrated NW growth techniques without a catalyst. In this paper we present some arguments to
explain highly anisotropic growth of NWs based on the CBE (Chemical Beam Epitaxy) growth of self-induced
InAs NWs on silicon.
The growth of NWs proceeds in a two stage protocol: low temperature nucleation and high
temperature growth steps. InAs NWs were grown in a RIBER C 21 CBE machine on Si (111) substrates.
Tertiarybutylarsine (TBA) and trimethylindium (TMI) were used as As and In sources, respectively. TBA was
pre-cracked in the injector at 1000 °C. We believe that the low temperature step helps nucleation of NWs,
while the high temperature (HT) step is required to start anisotropic growth [2].
Here we present some arguments explaining highly anisotropic growth. First, we suppose that the
InAs (111) surface of the NW top facet is likely to exhibit reconstruction with As trimmers on top of the As
layer. Thus, the arsenic part of the bilayer should form almost instantaneously and the nucleation would
require the completion of only the In layer. Since the nucleation requires the completion of the In layer only,
the nucleation barrier is reduced to approximately one half of its value on the side facets. Due to steep
exponential dependence of the nucleation rate (and the resulting growth rate) on the nucleation barrier, the
axial growth rate will be an order of magnitude higher than the radial one.
Much faster growth on the NW top with respect to the side facets also requires diffusion transport of In
adatoms to the top. Indium will migrate to the top only if the chemical potential there is lower than at the NW
sidewalls [3]. This property is ensured simply by the fact that the top facet is a more efficient sink of In
adatoms relative to the side facets and therefore the In concentration on the NW top is the lowest. The
concentration gradient gives rise to a diffusion flux to the top. In this sense, the top facet acts as a material
collector for In adatoms. Under As-rich conditions, catalyst-free growth of InAs NWs is expected to be limited
by surface diffusion of In, similarly to the case of self-induced GaN nanowires under high nitrogen flux [2].
One might argue that the concentration of In adatoms on the NW top is determined by crystallization
rate and the latter is determined by the As flux. Yet, the radial growth rate is limited by the In adatoms
concentration on the sidewalls which is determined by the difference of impingement flux and diffusion flux to
the top.
In summary we suppose that in case of self-induced NW growth the axial growth rate of NW is mainly
determined by the V-element flux, while the radial growth is controlled by the residue amount of III –element,
which cannot be consumed by the axial growth at the NW tip. This effect is partly hidden by the dependence of
the pyrolysis efficiency of one III group precursors on the V group precursors pressure.
[1]Ercolani, D.;Rossi,F.; Li, A; Roddaro, S.; Grillo, V.; Salviati, G.; Beltram, F.; Sorba, L. Nanotechnology 2009,
20, 505605.
[2] Consonni, V.; Dubrovskii, V.G.; Trampert, A.; Geelhaar, L.; Riechert, H. Phys. Rev. B 2012, 85, 155313.
[3] Dubrovskii, V.G.; Sibirev, N.V.; Harmand, J.C.; Glas, F. Phys. Rev. B 2008, 78, 235301.
S10-P14
Growth and characteristics of InAlAs/AlGaAs quantum dots depending on
annealing temperatures
Soo Yeon Kim1, Jin-Dong Song1, Il Ki Han*1
1
Center for Opto-Electronic Convergence Systems, Korea Institute of Science & Technology, , Seoul 136-791 (Korea)
Semiconductor based quantum dots (QDs) have been attractive because of their promising
applications in optoelectronic devices, such as laser diodes, solar cells, and single photon sources
[1]. The prospect application of QDs has led to substantial research efforts to grow various kinds of
QDs [2].
Recently, light sources with emission wavelength of 808 nm have received attention because of
their industrial applications for material process and medical equipment, etc. However, few studies
on the material growth for the light sources with the emission wavelength of 808 nm have been
reported. Although there have been studied on the growth of InGaAsP/InGaAlAs based quantum
wells, the material system suffers from small band offset, resulting in carrier overflows, which is
inherent problems of the fabrications for the high-efficiency and high-power light sources.
Studies concerning the structural and the optical properties of self-assembled QDs using rapid
thermal annealing have been performed to improve the quality of QDs [3]. Among the several types
of quantum structures, InAlAs/AlGaAs QDs have emerged as excellent candidates for highefficiency LEDs because of their high carrier confinement [4]. Even though some studies
concerning the formation and the physical properties of InAlAs/AlGaAs QDs have been conducted,
few investigations on the influences of growth and annealing temperatures on the structural and the
optical properties of the QDs have been performed.
In this study, we report data for the effects of growth and annealing temperatures on the
structural and optical properties of InAlAs/AlGaAs QDs grown by molecular beam epitaxy. Atomic
force microscopy and photoluminescence (PL) measurements were performed to investigate the
structural and optical properties of the InAlAs/AlGaAs QDs, respectively. While the (E1-HH1)
peak of the PL spectra shifted toward larger energy with increasing up to an annealing temperature
of 700 oC, it shifted toward lower energy above 700 oC. PL spectra for the InAlAs/AlGaAs QDs
annealed at 700 oC showed that the dominant peak appeared at 818 nm, which approximately
corresponded to a 808 light source. This results help to grow InAlAs/AlGaAs QDs for the emission
wavelength of 808 nm.
References:
[1] D.H. Kim, Y. H. Lee, D.U. Lee, T.W. Kim, S. Kim, and S.W. Kim, Optics Express, 20(2012) 10476.
[2] C. Gilfert, V. Ivanov, N. Oehl, M. Yacob, and J.P. Reithmaier, Appl. Phys. Lett., 98(2011) 201102.
[3] T. Yokoi, S. Adachi, S. Muto, H. Sasakura, H.Z. Song, S. Hirose, and T. Usuki, Physica E, 29(2005) 510.
[4] H.Z. Song, M. Takatsu, H. Sasakura, S. Muto and N. Yokoyama, Phys. Lett. A, 368 (2007) 92.
S10-P15
GaN-ZnO solid solution for photocatalytic applications: Synthesis by Solution
Combustion technique and characterization
Sumithra Sivadas Menon1, Anirban Bhattacharyya 2,Somnath Chanda Roy3 ,Bhavana Gupta4, K. Baskar1,
Shubra Singh1*
1
Crystal Growth Centre,Anna University, Chennai-600025,India
Institute of Radio Physics and Electronics,University of Calcutta,Kolkatta-700009,India
3
Department of Physics, IIT Madras, Chennai-600036, India
4
Material Science Group, Indira Gandhi Centre for Atomic Research,Kalpakkam,-603102,India
2
GaN-ZnO solid solution has emerged as a successful and reproducible photocatalyst for
overall water splitting by one-step photo excitation, with a band gap in visible region [1]. When the
solid solution is formed, some of the Zn and O ions are replaced by Ga and N ions respectively and
there is a narrowing of band gap which is hypothesized as due to Zn3d-N2p repulsion. The
traditional method of synthesis of GaN-ZnO solid solution is by nitriding the oxides under constant
ammonia flow [2].Here we report a solution combustion technique for the synthesis of the solid
solution at a temperature below 500oC in a muffle furnace with the nitrates of Ga and Zn as
precursors and urea as the fuel. The as prepared samples showed change in color with the increased
concentration of ZnO in the solution. The structural, morphological and spectroscopic properties of
the samples were realized by Powder X ray diffraction, Scanning electron microscopy,
Transmission electron microscopy, Low temperature photoluminescence, Diffuse reflectance
spectroscopy, X ray photoelectron spectroscopy, FTIR etc. Thin films of the as prepared samples
were coated on ITO substrates by spin coating technique and photoelectrochemical studies were
performed. Finally the photocatalytic behavior of the GaN-ZnO nanopowders was found using
methanol as a scavenger. The details of the synthesis and characterization will be presented.
(a)
(b)
Figure. a)Diffuse reflectance spectroscopy of samples with varying Zn to Ga ratio
b) Low temperature photoluminescence spectroscopy of GaN-ZnO solid solution.
References:
[1] Kazuhiko Maeda., Kazunari Domen., J.Phys.Chem.C, 111(22) (2007) 7851-7861.
[2] Kazuhiko Maeda, Tsuyoshi Takata, Michikazu Hara, Nobuo Saito, Yasunobu Inoue, Hisayoshi
Kobayashi and Kazunari Domen, J.Am.Chem.Soc, 127(2005) 8286-8287
S10-P16
Cu Catalytic Growth of GaN Nanowires on Sapphire Substrate for p-type
behavior
Boopathi Kuppulingam*1, Bernard Humbert2and Krishnan Baskar1
1
Crystal Growth Centre, Anna University, Chennai-2. (India)
Institute of Materials, University of Nantes, Nantes.(France)
2
Abstract:
The Cu catalytic growth of GaN nanowires (NWs) on c-plane sapphire substrate was
investigated using thermal chemical vapor deposition (CVD) process. Impact of reaction
temperatures on the crystalline quality has been studied by high resolution x-ray diffraction and
Raman spectroscopy and confirmed that the crystalline structure of GaN NWs was wurtzite as
shown in Figure 1(a & b). The morphologies of the GaN nanowires were confirmed by scanning
electron microscopy. The diameter of NW was about 20-100 nm and length was ~5 µm.
Composition and impurities in GaN NWs were studied by EDX analysis. Hall-effect measurement
on GaN NWs gives the resistivity (ρ) as 5 Ω cm, hole mobility (µP) as 2.97 cm2/V s, hole
16
concentration (p) 4
cm-3. Room temperature Photoluminescence (PL) study shows that
the near band edge emission for GaN NWs was red shifted to 3.26 eV.
Figure 1. (a) XRD analysis of GaN NWs prepared at various temperatures. (b) The variation of E2(high) mode in Raman
spectra of GaN NWs.
References:
[1] Wang J C., Zhan C Z., Li F G., Appl Phys A, 76(2003) 609-611.
[2] Yohannes K., Dong-Hau Kuo., Mater sci semicond process, 29 (2015) 288-293.
[3] Look D C., Reynolds D C et al., Appl Phys Lett, 81 (2002)1830-1832.
S10-P18
PRECURSORS FOR CIGSe
MICRO-CONCENTRATOR SOLAR CELLS
K. Eylers1*, F. Ringleb1, B. Heidmann2,3, M. Schmid2,3, Ch. Symietz4, J. Bonse4, J. Krüger4, Th. Teubner1, T. Boeck1, and M. Ch. LuxSteiner3,5
1
2
Nanooptical Concepts for PV, Helmholtz Zentrum Berlin, Hahn-Meitner-Platz 1, 14109 Berlin, Germany
3
4
5
Leibniz Institute for Crystal Growth, Max-Born-Straße 2, 12489 Berlin, Germany
Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany
Federal Institute for Materials Research and Testing, Unter den Eichen 44-46, 12203 Berlin, Germany
Heterogeneous Material Systems, Helmholtz Zentrum Berlin, Hahn-Meitner-Platz 1, 14109 Berlin, Germany
[email protected]
*
Abstract:
Cu(In,Ga)Se2 (CIGSe) is an excellent absorber for highly efficient thin-film PV applications. However, high costs of raw materials for
the preparation of CIGSe are a limiting factor for its industrial competitiveness. An approach to tackle this problem is to reduce
material consumption, especially of indium, and increase the cell efficiency by concentrating the incident light onto micrometer-sized
CIGSe islands. In contrast to well-established macroscopic concentrator PV, micro-concentrators allow a better heat management
and a more compact module design. Furthermore, for a low concentration factor (in the range of 100x), as it is aimed for this project,
the requirements on light tracking are relatively low. A promising bottom-up approach for the preparation of ordered CIGSe microabsorbers is to use indium islands as precursors, which can be grown by PVD in well-defined arrays of nucleation centers that are
induced by femtosecond laser pulses on the substrate surface.
S10-P19
Effect of ZnO/B2O3 ratio on the crystal growth in zinc borosilicate glasses
Kullberg Ana Teresa Guerra1, Lopes Andreia Alexandra de Sousa 1, Veiga João Pedro Botelho1, Monteiro
Regina da Conceição Corredeira*1
1
Department of Materials Science, CENIMAT/i3N, Faculty of Sciences and Technology, Universidade Nova de Lisboa,
Campus da Caparica, 2829-516 Caparica, Portugal
Glass samples with a molar composition (64+x) ZnO - (16-x) B2O3- 20 SiO2, where x = 0, 1,
were successfully synthesized using a melt-quenching technique with no deterioration of the glassforming ability. Based on differential thermal analysis data, the produced glass samples were
submitted to a controlled heat-treatment at a selected temperature (615C and 620C) during a
holding time ranging from 10 to 36 hours. Under these heat-treatment conditions, transparent
nanocomposite glass-ceramics were obtained.
The crystallization of willemite (Zn2SiO4) within the glass matrix was confirmed by means of
X-ray diffraction (XRD) and scanning electron microscopy (SEM). The influence of temperature,
holding time and ZnO/B2O3 ratio on crystal growth was investigated. The mean crystallite size was
determined by applying Scherrer’s equation to the characteristic peak of XRD patterns. These
results were compared with those obtained by image analysis on the SEM microstructures. Both
methods suggested an increase of the crystallite size with time, temperature and ZnO/B2O3 ratio.
Further investigation will be related to the optical characterization of the produced transparent
nanocomposite glass-ceramics regarding their potential applications in photonics.
Acknowledgements: To FCT (Foundation for Science and Technology) Portugal, for financing MERA.NET/0010/2012 and UID/CTM/500025/2013.projects.
S10-P20
Synthesis and Characterization of HgI2 Nanostructures for Films Nucleation
Pérez Barthaburu María 1*, Galain Isabel2, Olivera Alvaro1, Bentos Pereira Heinkel1, Fornaro Laura1
1
Grupo de Desarrollo de Materiales y Estudios Ambientales, Departamento de Desarrollo Tecnológico, CURE,
Universidad de la República, Ruta 8 and Ruta 15, Rocha, Uruguay
2
Grupo de Desarrollo de Materiales y Estudios Ambientales, Cátedra de Radioquímica, Facultad de Química,
Universidad de la República, General Flores 2124, Montevideo, Uruguay
With the aim of controlling the first steps in HgI2 film growth onto amorphous substrates, we
studied the synthesis of HgI2 nanostructures. Nanostructures were obtained by two different
synthesis methods. In one procedure HgI2 was obtained from Hg(NO3)2 and I2 in ODE at a constant
temperature of 70 ºC. The synthesis time was varied between 0 and 4 hours. In other procedure
Hg(NO3)2, KI or NaI were used for obtaining HgI2 in water. Samples were then subjected to an
hydrothermal treatment at a constant temperature during 2, 10, 19 and 24 hours. All samples were
centrifuged and dried in a laboratory oven. Both aforementioned methods are facile for obtaining
HgI2 nanostructures and easily scalable. HgI2 tetragonal phase was confirmed by powder X-ray
diffraction. Nanostructures were characterized in their morphology by transmission electron
microscopy and in their size also by the Scherrer method when possible. We observed that
nanostructures obtained in ODE were more stable against the electron beam while the ones
subjected to the hydrothermal treatment were more labile, sublimating/evaporating completely
during observation. In between samples obtained in ODE at different synthesis times, the one
performed during 4 hours yielded the best results in terms of morphology and size distribution.
Crystalline round nanostructures between 2 and 40 nm in size inserted in elongated structures were
observed in the former sample. TEM images of samples synthesized in ODE and with hydrothermal
treatment can be seen in Figure 1. HgI2 nanostructures were used as nuclei for nucleation onto
amorphous substrates. They were deposited onto ITO coated and uncoated flat silica glass by spin
coating. The morphology of this mechanical nucleation was studied by atomic force microscopy.
Further film growth was performed onto the nucleations by the physical vapor deposition method to
study nucleation influence. This mechanism of HgI2 nucleation is very promising for improving the
film growth orientation and therefore the current applications of this material, as far as for opening
new ones.
Figure 1. HgI2 nanostructures: a- synthesized in ODE. b- after hydrothermal treatment S10-P21
Synthesis and investigation of hexagonal modification NaY1-x-yYbxEryF4
Mayakova Mariya*1, Fedorov Pavel1, Kuznetsov Sergey1, Voronov Valerii1,
Pominova Daria1, Ryabova Anastasia1, Baranchikov Alexander2
1
Prokhorov General Physics Institute, Russian Academy of Sciences, 119991, Vavilov Str., 38, Moscow (Russia)
2
Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences,
119991, Leninsky prospect 31, Moscow (Russia)
Interest in synthesis and study of fluoride powders is rapidly increased recently. An unique set
of physical and chemical properties of fluorides cause the possibility of using fluoride powders in
various fields of science and technology. Fluoride powders can be used as the precursors for laser
ceramics and single crystals preparation, for different biomedical applications.
NaYF4 is one of the most efficient phosphors. NaYF4 crystallizes in two polymorphic
modifications: the high-temperature cubic (fluorite structure type) and low-temperature hexagonal
(gagarinite structural type). According to the literature data, erbium and ytterbium doped lowtemperature hexagonal modification is high efficiency up-conversion matrix. There are many
methods for the synthesis of low-temperature modification NaYF4, but most of them involve
technical difficulties. In this paper we used the method of spontaneous crystallization from the melt
for the synthesis of NaYF4 and NaY1-x-yYbxEryF4 (x, y = 1 ÷ 10 mol.%) hexagonal modification.
The optimal synthesis conditions (temperature synthesis, the amount of solvent, the excess of the
fluorinating agent, additional heat treatment conditions) were determined. Single-phase solid
solutions with the gagarinite structure confirmed by x-ray diffraction were synthesized. The
morphology of the synthesized powders was studied by scanning electron microscopy (figure 1).
Large particles are hexagonal morphology hollow inside, and the outer walls have a thickness about
50 nm. Ytterbium and erbium doped synthesized NaYF4 samples showed high values of the energy
yield of up-conversion luminescence.
Figure 1. Scanning electron microscopy image of the powder NaYF4
S10-P22
Hydrothermally Grown Arrays of ZnO Nanorods on Patterned Substrates
Jan Grym1*, Roman Yatskiv1, Jan Vaniš1, Jiří Slabý 1, Jaroslav Maixner2
1
Institute of Photonics and Electronics CAS, Chaberská 57, Prague 8 (Czech Republic)
Central Laboratories, Institute of Chemical Technology, Technická 5, Prague 6 (Czech Republic)
2
Semiconductor one-dimensional (1D) nanostructures possess a vast number of remarkable
physical and chemical properties thanks to their high aspect ratio at nanoscale dimensions. ZnO is a
direct wide bandgap semiconductor crystallizing in the wurtzite structure with a series of unique
properties: a large exciton binding energy, which inhibits thermal activation and enhances light
emission at room temperature; good optical transmittance in the visible region; high optical gain;
piezoelectricity; room temperature ferromagnetism; mechanical stability given by the high melting
point and large cohesive energy; radiation hardness; or biological compatibility [1]. These
properties allow for applications of ZnO in UV light-emitting devices and detectors, field-effect
transistors, solar cells, piezoelectric nanogenerators, or chemical sensors [2]. For the majority of
these applications, upright standing arrays with controlled positioning, sizes, and physical properties
are preferred over the free standing 1D nanostructures, which require additional manipulation.
The upright standing arrays were prepared by hydrothermal growth on Si substrates with a ZnO
seed layer and on GaN epilayers patterned by e-beam lithography (fig. 1) or by focused ion beams.
Electrical contacts were formed by a variety of techniques (see schematics in fig. 2) to study the
electrical charge transport. The transport properties were correlated with the structural and optical
properties investigated by x-ray diffraction and photoluminescence spectroscopy.
Figure 1. Example of the array of ZnO 1D
structures grown on GaN substrate patterned
by e-beam lithography.
Figure 2. Schematics of different techniques to characterize electrical
properties of ZnO 1D structures and their arrays.
This work has been supported by the Czech Science Foundation project 15-17044S and by the EU COST
Action TD1105 – project LD14111.
References:
[1] Ahmad M., Zhu J., Journal of Materials Chemistry 21/3 (2011) 599-614.
[2] Xu S., Wang Z.L., Nano Research 4/11 (2011) 1013-1098.
S10-P23
Synthesis of BiI3 nanoparticles through hydrothermal method intended for
preparing ionizing radiation detectors
Aguiar Ivana1*, Mombrú Maia1, Pérez Barthaburu María2, Fornaro Laura2
1
Universidad de la República, Av. General Flores 2124, Montevideo (Uruguay)
2
Grupo de Desarrollo de Materiales y Estudios Ambientales, Departamento de Desarrollo Tecnológico, Centro
Universitario Regional del Este, Universidad de la República, Ruta 9 and Ruta 15, Rocha (Uruguay)
Compound semiconductors of heavy metal iodides such as BiI3 have been widely studied due to
their properties as materials for room temperature gamma and X-ray detectors, such as high atomic
number of their elements, high density and high atomic absorption, which means high counting
efficiency [1]. Recently, nanostructures of these compounds are being synthesized due to their
capacity of being pressed into pellets, which comprises a new way of constructing detectors much
simpler than the crystal growth. The hydrothermal method with selective precipitation was chosen
as a suitable route for obtaining BiI3 nanoparticles. BiCl3 and NaI were used as precursors and
oxalic acid was used as capping agent to study its influence in size and morphology. The
nanoparticles were characterized by XRD, FTIR and TEM. Nanoparticles with oxalic acid of the
first precipitation range 9-10nm in diameter with round morphology. The same morphology was
observed in the second precipitation, however slightly smaller in size, 6-7 nm in diameter (Figure
1). The characterizations performed to BiI3 synthesized without capping agent proved that the
desired product is obtained as well, but with particles with a size about 20 nm. Pellets were
fabricated with the nanoparticles and detectors were constructed with them. The particles reported
here have better uniformity in size than the ones obtained in solution [2], showing that the addition
of oxalic acid improves the properties of the final particles. The detectors showed resistivities of
1010-1011 Ω.cm and respond to a 241Am source. These preliminary electrical and response to
radiation studies performed to detectors are promising, and encourage us to deep into the
development of this kind of detectors.
Figure 1. BiI3 nanoparticle obtained through hydrothermal synthesis with oxalic acid as capping agent. References:
[1] M. Overdick, C. Baumer, K.J. Engel, J. Fink, C. Herrmann, H. Kruger, M. Simon, R. Steadman, G.
Zeitler, IEEE Trans. Nucl. Sci (2009) 56, 1800-1809.
[2] L. Fornaro, I. Aguiar, M. Pérez Barthaburu, A. Olivera, I. Galain, M. Mombrú, J. Cryst. Growth, 401
(2014) 489-493.
S10-P24
HgS nanostructures for the development of hybrid active layers
Galain Isabel*1, Pérez Barthaburu María2, Aguiar Ivana1, Fornaro Laura2
1
Universidad de la República, Av. General Flores 2124, Montevideo (Uruguay)
2
Grupo de Desarrollo de Materiales y Estudios Ambientales, Departamento de Desarrollo Tecnológico, Centro
Universitario Regional del Este, Universidad de la República, Ruta 9 and Ruta 15, Rocha (Uruguay)
In recent years the use of semiconductor nanoparticles in nanostructured solar cells and hybrid
organic-inorganic solar cell has increased. The incorporation of inorganic nanostructures as electron
acceptors provides advantages to the solar cells performance, for example, by altering the cells
absorption profile [1-2].
For this reason, we synthesized HgS nanostructures by the hydrothermal method in order to use
them in hybrid organic-inorganic solar cells. We employed different mercury sources (HgO and
Hg(CH3COO)2) and polyvinylpyrrolidone (PVP) or hexadecanethiol (HDT) as capping/stabilizing
agents for controlling size, crystallinity, morphology and stability of the obtained nanostructures.
We also used thiourea as sulfur source, and a temperature of 180ºC during 6 h.
Synthesized nanostructures were characterized by powder x-ray diffraction, diffuse reflectance
infrared Fourier Transform, transmission electron microscopy, and electron diffraction.
When PVP acts as stabilizing agent, the mercury source has influence on the size of the betaHgS nansostructures obtained, but not in their morphology. HDT has control over
nanostructures´size and depending on the relation Hg:HDT, we obtained a mixture of alpha and
beta HgS which can be advantageous in its application in solar cells due to absorption in different
spectral regions. The smallest obtained nanostructures have an average diameter of 20 nm when
using HDT as capping agent, as can be seen in Figure 1.
Results obtained are very promising and represent important advances for the improvement of
hybrid solar cells.
Frequency
Nanostructure size distribution
50
45
40
35
30
25
20
15
10
5
0
5
10
15
20
25
30
35
40
45
50
Particle Feret's diameter (nm)
Figure 1.TEM Image of HgS nanostructures obtained with HDT as capping agent.
References:
[1] Wright M., Uddin A., Solar Energy Materials & Solar Cells 107, 107 (2012) 87-111.
[2] Higginson K. A., Kuno M., Bonevich J., Qadri S. B., Yousuf M., Mattoussi H., J. Phys. Chem. B, 106
(2002) 9982-9985.
S10-P25
Growth of ZnO nanorods on carbon fibers for in-situ stress measurements
Culiolo Maurizio*1, Delmonte Davide1, Villani Marco1, Marchini Laura2, Bercella Rocco2,
Calestani Davide1, Coppedè Nicola1, Solzi Massimo3, Zappettini Andrea1
1
IMEM-CNR, Parco Area delle Scienze 37/A, 43124 Parma (Italy)
Bercella s.r.l., via Enzo Ferrari 10, 43040 Varano de’ Melegari (PR), (Italy)
3
Dipartimento di Fisica e Scienze della Terra “Macedonio Melloni” – Università degli Studi di Parma, Parco Area
delle Scienze 7/A, 43124 Parma (Italy)
2
Carbon fiber based composites (CFC), owing to the exceptional ratio between mechanical
properties and weight, represent a fundamental technology for several applications, ranging from
aerospace to automotive, from civil infrastructure to biomedical engineering. Due to the intense
mechanical stress often involved, strain and deformation on CFC made structures have to be
constantly monitored. Furthermore univocal mechanical models doesn’t exist, since carbon fiber
(CF) patches can be textured with CF oriented in different directions depending on necessity.
Nowadays strain sensing on CFC is carried out with optical fiber and piezoelectric ceramics.
However this technologies present three main drawbacks, that are large size (compared to CF size),
weight addition to the structure and use of precious metals wires. Recently the use of different
materials functionalized with piezoelectric zinc oxide (ZnO) nanostructures started to get a foothold
for sensing and energy harvesting.
Piezoelectric effect, owing to its dual peculiarity relating deformation with electric properties,
lends itself to both sensing and actuating applications. Therefore functionalization of CF with ZnO
piezoelectric nanostructures allow to realize a fully integrated piezoelectric sensor/actuator within
CFC structure, thanks also to the fact that conductive CF themselves act as electrical wires.
The ZnO in-situ growth is made by a low-temperature and low-cost two-step process:
functionalization of CF with ZnO seed-layer by Successive Ionic Layer Adsorption and Reaction
(SILAR) technique and growth of ZnO nanorods by chemical bath deposition.
Measuring the piezoelectric effect in ZnO nanostructures is still a debatable topic, since the
typical I-V characterization is not generally accepted. In this work piezoelectric investigation is
carried out for the first time on such structure using ferroelectric virtual ground, PUND and DHM
techniques. The emergence of a voltage-invariant capacitance variation upon stress application is
ascribed as the fingerprint of piezoelectricity.
Figure 2. Depiction of the device structure: crossed CF functionalized with ZnO seed-layer and
nanorods.
S10-P27
High-Density n-ZnSe Nanowires Grown on CdS/ITO Glass for Hydrogen Evolution
by Dual Visible Light Absorption
Ki-Hyun Cho, Kyung-Shik Kim, Jong Yeon Choi, and Yun-Mo Sung
Department of Materials Science & Engineering, Korea University, Seoul 136-713, South Korea
For the first time ZnSe nanowires were successfully grown on a substrate by a low-temperature
solution method. Bi catalysts were used for the solution-liquid-solid (SLS) growth of ZnSe
nanowires. They were highly crystalline and in zinc blende structure. Their average diameter and
length were ~30 nm and ~2-3 m, respectively. There exist only a few papers reporting the
application of ZnSe for water splitting. The role of ZnSe (~2.7 eV) was only sensitizing TiO2
having wide band gap (~3.2 eV) under visible light illumination.
In this study we demonstrate the combination of n-ZnSe and n-CdS for the construction of
effective Z-scheme water splitting. Both ZnSe and CdS (energy band gap of ~2.5 eV) can be
activated under visible light. At the thermal equilibrium, to meet the Fermi energy level the energy
bands of ZnSe sift down to positive potential and those of CdS shift up to the negative potential. As
a result, we could obtain a higher reduction (electron) potential from CdS and a higher oxidation
(hole) potential from ZnSe, and in turn Z-scheme could be completed between ZnSe and CdS. The
excited electrons in CdS can move to a Pt electrode and reduce hydrogen ions to evolve hydrogen
gas, while the excited electrons in ZnSe can combine with holes in CdS at the ZnSe/CdS interface,
eliminating the photocorrosion problem of CdS. The holes in ZnSe can oxidize water to evolve
oxygen gas.
The excited electrons from CdS layer could transfer to the Pt electrode through ITO substrates
and the photocurrent density was measured to be ~2.9 mA/cm2 at 0 bias voltage under visible light
irradiation. This photocurrent value is an almost two times higher value than that from only n-ZnSe
nanowire anodes. This increased photocurrent density could originate from the effective electron
and hole separation of ZnSe by the formation of Z-scheme and increased reduction and oxidation
potentials by energy band aligning between ZnSe and CdS.
This paper demonstrates the first successful growth of ZnSe nanowires on a substrate by a
solution method and the first try of using ZnSe as a hole carrier for the Z-scheme water splitting.
Large-area n-ZnSe/n-CdS photoanodes can be achieved using the low-temperature SLS growth.
S10-P29
Mass-transport driven growth dynamics of AlGaAs shells deposited by
metalorganic vapor phase epitaxy around dense GaAs nanowire ensembles
Ilio Miccoli1, Paola Prete2, Nico Lovergine*1
1
Dip. di Ingegneria dell’Innovazione, Università del Salento, I-73100 Lecce, Italy
Istituto per la Microelettronica e Microsistemi, CNR, UOS Lecce, I-73100 Lecce, Italy
2
III-V compounds nanowires are expected to impact several device technology fields, ranging
from nanoelectronics, to nanophotonics, and photovoltaics, by offering both unprecedented
materials properties and novel device geometries/functionalities. Radial modulation of nanowire
composition and/or doping in the form of core-shell and core-multishell nanowire heterostructures
has been proposed for novel nano-LEDs/-lasers [1,2]. In order to exploit MOVPE technology for
the fabrication of such devices, good control over the growth process of radially-heterostructured
nanowires is necessary. While many efforts have been devoted in understanding/modelling the Aucatalysed (VLS) growth of III-V nanowires, much less is known on the growth dynamics of shell
materials by the conventional (Vapor-Solid) MOVPE around free-standing core nanowires.
We report on a detailed experimental analysis of AlGaAs shell growth by MOVPE around freestanding GaAs nanowires, the latter self-assembled by the Au-catalyzed process on (111)B-GaAs
wafers or GaAs/(111)Si hetero-substrates [3]. We demonstrate that the vapour mass-transport
supply of III-group species during shell growth couples with the nanowire size (e.g. their diameter)
and their local surface density on the substrate to determine the actual shell growth rate. A vapor
mass-transport model is proposed and validated, describing the MOVPE growth dynamics of the
shell material around dense ensembles of GaAs nanowires [4]. We predict a complex (non-linear)
dependence of the shell growth rate on initial GaAs nanowire diameters, heights, local densities on
the substrate, and deposition time (see Figure 1). Present results constitute a significant step towards
the controlled fabrication of core-shell and core-multishell nanowire heterostructures by MOVPE.
(a)
(b)
Figure 1: Average diameter of GaAs-AlGaAs core-shell nanowires as function of (a) their substrate
surface density (NW) after 10 min shell growth, and (b) the shell growth time for different NW.
References:
[5] B. Mayer, D. Rudolph, J. Schnell, S. Morkotter, J. Winnerl, J. Treu, K. Muller, G. Bracher, G.
Abstreiter, G. Koblmuller, Nat. Comm. 4 (2013) 2931.
[6] K. Tomioka, J. Motohisa, S. Hara, K. Hiruma, T. Fukui, Nano Lett. 10 (2010) 1639.
[7] I. Miccoli, P. Prete, F. Marzo, D. Cannoletta, N. Lovergine, Cryst. Res. Technol. 46 (2011) 795.
[8] I. Miccoli, P. Prete, N. Lovergine, submitted (2015).
S10-P30
Laser processed oxides for optoelectronics and bio applications
Soares Rosa1, Rodrigues Joana1,Santos Nuno1, Holz Tiago1, Ferreira Nuno1, Sousa Marta1,Ferro Marta2
Fernandes António1, Cunha António1, Monteiro Teresa 1, Costa Florinda*1
1
2
Departamento de Física & I3N, Universidade de Aveiro 3810-193, Aveiro (Portugal)
Depart. de Eng. de Materiais e Cerâmica & CICECO, Universidade de Aveiro 3810-193, Aveiro (Portugal)
Laser processing is known as one of the most ultimate techniques in light based manufacturing
to develop technological devices. Additionally, the use of high power lasers constitutes nowadays
an alternative methodology to the chemical routes in the materials synthesis/growth. Bulk crystals,
thin films and nanoparticles/nanostructures are currently achieved by laser processing techniques.
In this work, light emitters based on lanthanide ions (Ln3+) doped zirconia system were grown
as singe crystals and nanoparticles (NPs). Laser floating zone (LFZ) [1] technique was explored to
grow high quality single crystals while NPs were produced by the pulsed laser ablation in liquid
(PLAL) [2]. PLAL process was used to produced Tb 3+ and Eu 3+ doped yttria stabilized zirconia
(YSZ) NPs in water (figure 1), for application in biolabeling and bio-imaging based in time
resolved (TR) luminescence detection. Moreover, YSZ NPs with upconversion (UC) luminescence,
with enhanced prospects as luminescent source in bio-imaging, such as the ones co-doped with
Tm3+ and Yb3+ ions were also produced by PLAL.
Additionally, wide band gap semiconductors such as ZnO and SnO2 with high structural and
optical quality were grown as micro and nanocrystals with distinct morphologies by the laser
assisted flow deposition (LAFD) method. This technique allows the synthesis of materials having
close melting and evaporation points with controllable morphology by an adequate choice of the
growth parameters [3,4]. The use of the LAFD technique to grow functional ZnO nanostructures
(nanoparticles and tetrapods) working as nano templates for different approaches, namely as dyesensitized solar cells (DSSCs) [5], will be highlighted.
a)
b)
Energy (eV)
4.5 4
3.5
3
2.5
1.4
1.0
0.4
D3 F5-2
5
7
D47F2
5
PL: 277 nm
0.2
x 80
PLE @ 544 nm
0.0
250
D47F3
x 20
5
D47F6
5
D37F6
5
0.6
D47F4
0.8
5
Normalized Intensity
1.2
2
D47F5
5
YSZ: 1% Tb colloid
RT
300
350
400
450
500
550
600
650
Wavelength (nm)
Figure 1. a) TEM images and b) RT PL and PLE of the YSZ:Tb NPs produced by PLAL
References:
[1] M.R.N. Soares et al., J. Appl. Phys.,109 (2011) 013516.
[2] M.R.N. Soares et al., RSC Adv., 5 (2015) 20138
[3] J. Rodrigues et al., Proc. SPIE, SPIE OPTO, (2015) 89871F
[4] N. F. Santos et al., Phys. Chem. Chem. Phys., 17 (2015) 13512-13519
[5] J. Rodrigues et al., submitted (2015)
700
750
800
S10-P31
Obtaining of II-VI compound single crystal substrates with controlled electrical
properties and prospects of their application for manufacturing nanotemplates
Colibaba Gleb* 1,2, Monaico Eduard3, Tiginyanu Ion3, Goncearenco Evgenii1, Inculet Ion1
1Moldova
State University, A. Mateevici 60, MD-2009, Chisinau, Moldova
2Kazan
3
Federal University, Kremlevskaya 18, 420008, Kazan, RF
Technical University of Moldova, Stefan cel Mare 168, MD-2004, Chisinau, Moldova
*
Wide band-gap II-VI semiconductors are perspective materials for the fabrication of nanoporous matrices
(NM) or nanotemplates. The conductive semiconductor nanotemplates possess wide potential for the growth
of networks of nanowires, nanotubes and nanodots based on various materials. These nanostructures are
promising for use in high-efficient solar cells with nanostructured p-n junctions, photonic elements, electronic
sensors etc. The easiest and cost-effective method to obtain NM is electro-chemical etching (ECE), which,
however, depends on conductive properties of the substrates.
The conditions of growing homogenious ZnSe and ZnS single crystals by physical vapour transport
method, and also CdS, ZnSSe, ZnCdS and ZnO single crystals by chemical vapour transport method based
on HCl vapors are discussed. Based on the results of investigation of electrical properties of the samples with
various doping levels, the prospect of examined technology for manufacturing the substrates of these
compounds with large area and controlled n-type electrical conductivity varried up to 20, 0.3, 100, 0.3, 30, and
20 (Ω·cm)-1, respectively, is estimated.
The results of nanostructuring II-VI compound substrates using various acid electrolytes are shown. The
prospect of using ZnSe and ZnCdS compounds for obtaining nanopore arrays with pore diameter down to 30
nm and pore depth up to 1 mm, as well as ZnO substrates for nanohills or nanopits arrays, are demonstrated.
The limitations for producing the similar structures on the basis of ZnS and ZnSSe substrates, and features of
etching polar ZnO substrates are shown.
Figure. Scanning electron microscope image in cross-section of porous Zn0.5Cd0.5S layer (a), Zn0.6Cd0.4S multilayer (b);
Oxide face of ZnO substrates anodized in K2Cr2O7:H2SO4:H2O electrolyte (c), HNO3:H2O electrolyte (d), HCl:H2O
electrolyte (e) and Zn face of ZnO substrates anodized in HCl:H2O electrolyte (f).
This work was supported by the Moldavian National grant No.14.819.02.14A, and partially by the Russian Government (agreement
No.02.A03.21.0002) to support the Program of Competitive Growth of Kazan Federal University among World’s Leading Academic
Centers.
S10-P32
Surface Morphological Analysis of nano-patterned c-plane sapphire substrates
using 450KeV oxygen ions
I. Davis Jacob1, G.K.Priya Merline1, K. Asokan2, K. Baskar1 and M. Chitra1*
1
2
Inter University Acceleration Centre, New Delhi (India)
*email for correspondence: [email protected], [email protected]
Abstract: Nano-patterning using implantation of 450KeV oxygen ions on the sapphire substrates
causes restructuring and creates nucleation centres on the surface of c-cut sapphire wafers that has a
direct impact on the growth kinetics in the Two-step nucleation and MOCVD growth of the GaN
buffer layers and the dislocation density arising due to the lattice mismatch between the sapphire
and GaN layers. In this study, the c-cut wafers of sapphire are annealed at 1350°C for about 12
hours. Annealing widens the terraces on the c-cut (0001) plane of sapphire where steps are clearly
visible indicating a miscut angle during the chemo-mechanical polishing of sapphire wafers.
Annealing improves the crystallinity of sapphire. Implantation of 450KeV oxygen ions were carried
out in the fluence range of 5x1011 ions/cm2 to 1x1014 ions/cm2. AFM analysis reveals that low
fluence implantation of oxygen causes horizontal streaks of damage in the crystallinity on the c-cut
surface whereas higher fluence implantation of oxygen causes tiny hillocks of crystal damage.
S10-P33
Surface modification of Cu2O/p-CuxS thin films for Liquefied Petroleum Gas
sensing
Bandara Nayana Dammika a,b,Jayathileka Charith a,d, Gunewardene Siyath a, Dissanayake Dhammike.c,
Jayanetti Sumedhaa,*
a Department
of Physics, University of Colombo, Colombo 03, Sri Lanka
Department of Physics, Open University of Sri Lanka, Nawala, Nugegoda, Sri Lanka
c Department of Chemistry, University of Colombo, Colombo 03. Sri Lanka
d Department of Physics, University of Kelaniya, Kelaniya, Sri Lanka
*referring author E-Mail: [email protected]
b
Liquefied petroleum (LP) gas is widely used, for domestic, commercial and industrial purposes
around the world. It is an extremely inflammable hazardous gas. Efficient sensing of unsafe levels of
LP gas will help to minimize the risks of accidents. This work focuses on a novel mechanism to detect
LP gas effectively using electrochemically deposited n-type cuprous oxide thin films on Ti substrates
in acetate bath with surface modification through sulphidation followed by passivation, which forms a
thin film n-Cu2O/p-CuxS semiconducting heterostructure. Detection can be achieved at operating
temperatures <100ºC and is a relatively simple and low cost technique.
In order to fabricate n-Cu2O/p-CuxS heterostructures, electrochemically deposited n-type
cuprous oxide (n-Cu2O) thin films on Ti substrates in acetate bath were sulphided using Na2S.
Subsequently these thin film structures were passivated using (NH4)2S vapor. As a result of
passivation, the sensitivity (fractional change in thin film resistance) of thin films were enhanced when
exposed to liquefied petroleum (LP) gas at 45ºC with quick response and recovery characteristics.
The scanning electron microscopy (SEM) showed that the unsulphided n-type Cu2O thin films
exhibited typical polycrystalline surface morphology, while SEM of sulphided and passivated thin films
revealed micro/nano crystalline surface morphological features with porous structures(Figure 1). As
expected, the thin film structures obtained through sulphidation followed by passivation of n-type Cu2O
films decreased the film resistance (1 kΩ) in comparison to the resistance (1 MΩ) of the
unsulphided n-type Cu2O thin films.
Upon exposure to LP gas, the resistance of these thin film structures increased while sensitivity to
LP gas depended on the electrochemical deposition time, the passivation time and the sensing
temperature. The crucial factor for the recovery of the resistance to its ambient resistance when the
exposure of sulphided and passivated thin film structures to LP gas was stopped, was an optimal ntype Cu2O thin film thickness. The highest sensitivity of 48 %.was recorded when the exposure of thin
film structures fabricated by electrodepositing n-type Cu2O thin films for 45 min., sulphided and
passivated for 5 s and maintained at a sensing temperature of 45 ºC to LP gas.(Figure 2)
1μm Figure 1. SEM picture of sulphided and passivated
Cu2 O thin films
Figure 2. Sensitivity variations of sulphided and passivated
Cu2 O thin films with the exposure of LP gas
SESSION 11
Novel Materials and Structures
In-situ observations of the catalytic growth of nanomaterials
Stephan Hofmann
Department of Engineering, University of Cambridge, United Kingdom
With a focus on diverse applications in the electronics and display industry, we aim at developing
integrated process technology for nanomaterials, like semiconducting nanowires. In order to go
beyond empirical process calibrations, we systematically use in-situ metrology to reveal the
mechanisms that govern the growth, interfaces and device behaviour of these nanomaterials in
realistic process environments. This talk will focus on recent results for Si and Ge nanowires with a
particular emphasis on fundamental aspects and the use of these structures as model systems to
explore more generic aspects of phase behaviour, nucleation and interface dynamics in nanoscale
systems.
Video-rate lattice-resolved environmental transmission electron microscopy (ETEM) of Au
catalyzed Ge nanowire (Ge NW) growth allows us to directly observe the formation of metastable
AuGe phases without quenching [1]. We rationalise the unexpected formation of these phases
through a novel pathway involving changes in composition rather than temperature. ETEM of Ge
NW growth also allows us to directly observe twin-mediated crystal growth. In contrast to the
classic twin plane re-entrant mechanism (TPRE) for bulk crystals, we find that the nanowire
geometry allows steady-state growth with a single twin boundary at the nanowire center [2]. Our
data allows us to focus on why a single twin leads to growth and to consistently interpret prior NW
literature, for example, reporting post-growth data of preferential impurity incorporation along twin
defects and the frequent observation of twins in NWs growing in the 112 direction. We propose
that the nucleation barrier at the twin plane re-entrant groove is reduced by the presence of a line
energy. Our results are of general validity and provide an important insight into the TPRE growth
process of bulk materials.
Forming reliable contacts is crucial in particular for nano-scale electronic devices. We show that
nanowires offer an ideal platform to study contact formation with ETEM allowing a record of
atomically resolved interface formation. We report on a new form of epitaxy that involves silicide
phase formation via the catalyst particle and offers a generic platform for seeding new crystals and
forming heterostructures (see Figure)[3].
Figure 1. In-situ TEM images showing the formation and incorporation of a nickel silicide (NiSi2) nanoparticle (colored
yellow) into a silicon nanowire during catalytic growth [3].
References:
[1] Gamalski et al., Phys. Rev. Lett. 108, 255702 (2012).
[2] Gamalski et al., Nano Lett. 14, 1288 (2014).
[3] Panciera et al., Nature Materials, DOI: 10.1038/NMAT4352 (2015).
Crystal engineering of molecular solids: "light" interactions for interactions with light.
Fabrizia Grepioni,a Simone d'Agostino,a Dario Braga,a Barbara Ventura,b Mirko Serib
a
b
Dipartimento di Chimica G. Ciamician, via Selmi, 2 - 40126 Bologna
Istituto ISOF-CNR, Via P. Gobetti, 101, 40219 Bologna, Italy.
Molecular crystal engineering, i.e. the design and synthesis of solid state molecular materials
with predefined properties, is used here to exploit non-covalent interactions to pre-arrange
buiding blocks in their crystalline state for properties modification and specific applications, all
involving the absorption of UV radiation.
Depending on the chemical complexity and/or application, crystals of appropriate size and
purity are required for characterization, chemical reactivity and applicative processes. Three
cases will briefly be presented here: (i) single crystal to single crystal photodimerization of
cinnamic acid derivatives and the effect of crystal size on the solid-state reactivity; (ii) cocrystallization as a tool to switch from fluorescence to phosphorescence in the solid state, and
the necessity of obtaining single crystals following a mechanochemical synthesis; (iii)
molecular crystals for dye-sensitized solar cells applications, and the single crystal vs.
polycrystalline material requirements on passing from characterization to photophysical
measurements and to thin-film deposition.
Chemical Vapor Transport towards new geo-inspired selenite based materials.
Marie Colmont*1, Vadim M. Kovrugin1,2, Oleg I. Siidra2, Sergey V. Krivovichev2 and Olivier Mentré1
1
Université Lille 1 Sciences et Technologies, UMR 8181 CNRS, Unité de Catalyse et Chimie du Solide
‘UCCS’, F-59655 Villeneuve d’Ascq, France
2
Department of Crystallography, St. Petersburg State University, University Emb. 7/9, 199034 St.
Petersburg, Russia
The demand for new noncentrosymmetric compounds is very strong because of their
possible interesting properties such as second-harmonic generation (SHG), piezoelectricity,
ferroelectricity or pyroelectricity. Particularly, Se4+ cation is of huge interest because of its
stereoactive lone pair of electrons usually assorted to asymmetric coordination environments. The
crystal chemistry of metal selenites is very rich and if cleverly used with other cations as Pb2+ or
Bi3+, chances to get asymmetric building units or NCS crystal structures are highly enhanced. From
an experimental point of view, CVT synthesis is a technique of choice because (1) of the high
volatility of SeO2, BiCl3 or PbCl2 used as precursors, (2) it is less used as other common synthesis
process giving more chances to get new crystal structures and (3) it provides a good opportunity to
simulate conditions in fumarolic environments in favor of stabilization of selenite phases.
In this presentation, after reminding experimental key parameters of CVT synthesis, the
investigation of three different systems (1) cоpper1, (2) lead2 and (3) bismuth chloroselenites3 will
be presented, including new crystal structures. Results from the cоpper system are shown in Figure
1. Crystals of K[Cu5O2](SeO3)2Cl3 were isolated in the source zone. The isotypic structure was also
obtained with Na instead of K and are related to the known mineral, ilinskite.
Figure 1. General scheme of the CVT method (a), the source zone of the tube (b), the crystals of
K[Cu5O2](SeO3)2Cl3 picked out from the source zone (c), and a common view of the sealed silica
tube after the CVT synthesis (d)
The authors sincerely thank the ANR (grant ANR-12-JS08-0012) for financial support.
References:
[1] V. M. Kovrugin, O. I. Siidra, M. Colmont, O. Mentré, S. V. Krivovichev, Mineralogy and
Petrology, 2015, DOI: 10.1007/s00710-015-0369-3
[2] V. M. Kovrugin, M. Colmont, O. I. Siidra, S. V. Krivovichev, O. Mentré, Crystal Growth and
Design, submitted
[3] Aliev, V.M. Kovrugin, M. Colmont, C. Terryn, M. Huvé, O.I. Siidra, S.V. Krivovichev, O.
Mentré, Crystal Growth and Design, 14(6), 2014, 3026-3034
Spectroscopic examinations of Lu3Al5O12: Pr single crystals.
Guzik Adam*1, Talik Ewa1, Pajączkowska Anna2, Szubka Magdalena1, Kusz Joachim1, Balin Katarzyna3,
Urbanowicz Piotr1
1
Department of Physics of Crystals, Institute of Physics, University of Silesia, Uniwersytecka 4, Katowice (Poland)
2
Institute of Electronic Materials technology,Wólczyńska 133, Warsaw, (Poland))
3
Department of Solid State Physics, Institute of Physics, University of Silesia, 75 Pułku Piechoty, Chorzów (Poland)
Luminescent materials are widely applied as converter screens in fluorescent lamps, LEDs,
emissive displays, x-ray and high energy particle detectors, and solid state LASERs. In most of the
application areas, the luminescent compositions are applied as polycrystalline powders, however,
some devices require single crystalline materials: e.g. solid state LASERs or positron emission
tomographs. Scintillators based on 5d-4f luminescence of Pr3+ are considered as good candidates for
detection of high-energy photons and particles. As compared to oxide scintillators based on 5d-4f
luminescence of Ce3+ , the 5d-4f emission of Pr3+ is faster and lies in a shorter wavelength range.
Among the garnet-type compounds Lu3Al5O12:Pr (LuAG:Pr) with its fast decay of 20 ns, light
yield 18000 ph/MeV which is more than twice higher than that of well-known and wide used
scintilator Bi4Ge3O12, relatively high density (6.7 g/cm 3) and Zeff (62.9) [1] is the most attractive.
Single crystal materials of Lu3Al5O12:Pr and (Lu0.75Y0.25)3Al5O12:Pr were grown by the
Czochralski method under nitrogen or argon atmosphere. Obtained crystals were analyzed by the
Laue diffractometry confirming single crystal form, single ion mass spectroscopy – giving
chemical composition as a function of crystal depth, magnetic measurements – information of the
Pr3+ ion concentration in sample, XPS electronic structure. The dielectric properties investigations
revealed ε' and ε'' as a function of temperature (80 - 400 K) and frequency (0.5 kHz – 5 MHz).
Figure 1. Distribution map of the Ca surface contaminator obtained by the SIMS method. Triangle etch pits
are visible. At right – dislocations with migrated contaminator into core of crystals are visible( the depth is
about 100 μm)
References:
[1] Ogino H., Yoshikawa A., Nikl M., Kamada K., Fukuda T., “Scintillation characteristics of Pr-doped
Lu3Al5O12 single crystals,” J. Crystal Growth 292, 239-242 (2006)
Crystal Growth from High-Pressure Melt and Chemical Vapor Transport of
(Si,Ge)-monopnictides, a new family of 2D-semiconductors
Céline Barreteau1, Baptiste Michon, Enrico Giannini*1
1
Department of Quantum Matter Physics, University of Geneva quai E.-Ansermet 24,CH-1211 Geneva 4 (Switzerland)
Layered semiconducting materials have recently grabbed the spotlight, particularly in the case
of van der Waals solids that can be exfoliated into atomically thin sheets. Tunable electronic
properties as well as new phenomena related to the electron confinement in one direction make
these materials highly appealing for novel electronic devices. A tremendous effort is being made on
binary transition metal dichalcogenides [1], but other families of compounds have been discovered
and deserve increasing consideration [2].
Binary monopnictides of Si and Ge (SiP, GeP, SiAs, GeAs, …) are a promising, but longtime
disregarded family of such materials, thanks to their structure made of strongly covalent slabs,
weakly bonded to each other by van der Waals forces, and their semiconducting nature exhibiting
band gap values in the range 0.6 – 1.3 eV. Processing and crystal growth of these compounds is
challenging [3] and in some cases has been elusive so far. The high volatility of the pnictogens
(particularly P) at rather low temperatures, and the high temperature needed for making Si and Ge
reactive, require dedicated unconventional growth processes for the bulk crystallization of these
materials.
We report the successful crystal growth of various members of this family by means of either
crystallization from the melt at high pressure in a cubic anvil hot press, or chemical vapor transport
in sealed quartz reactors using I2 as a transport agent, or even a particular combination of both
techniques. As a matter of fact, the direct vapor transport of phosphorous does not lead to the
inverse sublimation and growth of the wanted compound, nevertheless I2 proved to be successful in
transporting binary phosphide molecules from a precursor preformed at high pressure (in the GParange).
The as grown crystals easily cleave into very thin micaceous sheets and exhibit the expected
semiconducting behavior. The conditions for crystal growth are discussed with respect to the
thermodynamic phase equilibria suggested by the assessed phase diagrams. The optimization of the
growth conditions lead to the growth of mm-size layered crystals that can be mechanically
exfoliated and implemented into novel nano-electronic devices.
References:
[1] Chhowalla M., Shin H. S., Eda G., Li L.-J., Loh K. P., Zhang H., Nature Chemistry, 5 (2013) 263
[2] Miro´ P., Audiffred M., Heine T., Chem. Soc. Rev., 43 (2014) 6537
[3] Lee K., Synnestvedt S., Bellard M., Kovnir K., Journal of Solid State Chemistry, 224 (2015) 62
Superconductivity in single crystals of alkali metal intercalated iron chalcogenides
A. Krzton-Maziopa,1 E. Pomjakushina,2 K. Conder*2
1Chair
of Inorganic Chemistry and Solid State Technology, Warsaw University of Technology, Poland
2Laboratory
for Developments and Methods, Paul Scherrer Institute, Villigen, Switzerland
Interplay between superconductivity, magnetism and crystal structure in iron-based superconductors has
recently attracted a great interest. Alkali metal intercalated iron chalcogenide superconductors exhibit unique
behaviors which are not observed in other iron-based superconducting materials such as antiferromagnetic
ordering above room temperature and iron vacancies ordering. In this work synthesis, crystal growth, structural
and superconducting properties of the family of alkali metal (K, Rb, Cs) intercalated iron chalcogenides FeSe
with Tc around 30K are reported. Single crystals have been grown by the Bridgman method. X-ray and neutron
diffraction, micro x-ray fluorescence, magnetization and transport measurements have been applied to study
the crystals. It was found that in the crystals at least two phases are coexisting - one majority magnetic phase
and a diamagnetic minority phase, most probably, responsible for superconductivity. The phase separation
was stated in our samples by means of the muon-spin rotation (SR), x-ray and neutron diffraction and high
resolution electron backscatter diffraction.
Crystal growth of rare earth containing clathrates and mechanism of rare earth
incorporation into the clathrate cages
Andrey Prokofiev1*, Robert Svagera1, Monika Waas1, Johannes Bernardi2, and Silke Paschen1
1
Institute of Solid State Physics, Vienna University of Technology, Wiedner Hauptstr. 8-10, 1040
Vienna (Austria)
2
USTEM, Wiedner Hauptstr. 8-10, 1040 Vienna (Austria)
Type-I clathrates possess extremely low thermal conductivities, a property that makes them
promising materials for thermoelectric applications. They are guest-host systems in which a large
electropositive atom like Ba or alkali metals fills oversized polyhedral cavities in a covalently
bound Si, Ge, or Sn framework. It is the interaction of the vibration mode of the guest atom
(rattling) with the delocalized vibrations of the framework that results in the anomalously low
thermal conductivity. The incorporation of cerium (Ce) into one such clathrate, the type-I clathrate
Ba8Au6Si40, has recently been shown to lead to a drastic enhancement of the thermopower, another
property determining the thermoelectric efficiency [1]. This incorporation appeared to be feasible
only via a crystal growth process implying the crystallization of the clathrate phase from an offstoichiometric melt with an excess of Ce and Au. The developed floating zone technique was
realized in a mirror furnace. The technique was now applied to clathrates containing other rare earth
elements (RE). We discuss the mechanism of RE incorporation based on the trends in the clathrate
phase composition along the RE element range. Our investigation reveals that the RE content is
mainly governed by two factors, the residual cage space and the electron balance in the sense of the
Zintl concept [2]. The thermoelectric and magnetic properties of some RE clathrates are discussed.
References:
[1] Prokofiev A., Sidorenko A., Hradil K., Ikeda M., Svagera R., Waas M., Winkler H., Neumaier K., and
Paschen S. Nature Mat. 12 1096-1101 (2013)
[2] Sevov S.C.. Zintl phases. In Intermetallic Compounds, Principles and Practice: Progress;
Westbrook, J. H., Freisher, R. L., Eds.; John Wiley & Sons. Ltd.: Chichester, England, 2002; 113132.
Flux growth at 1230°C of cubic Tb2O3 single crystals and characterization of
their optical and magnetic properties
Matias Velázquez*1, Philippe Veber1, Grégory Gadret2, Olivier Plantevin3, Daniel Rytz4, Mark
Peltz4, Rodolphe Decourt1
1
LICB, UMR 6303 CNRS-Université de Bourgogne, Faculté des Sciences Mirande, 9 avenue Alain Savary, BP 47870,
21078 Dijon cedex (France)
3
4
FEE-GmbH, Struthstrasse 2, 55743 Idar-Oberstein (Germany)
2
In recent years, we have unveiled a new flux method for growing single crystals of cubic
rare earth sesquioxides, pure or doped, essentially for optical applications (lasers, scintillators,
Faraday rotators) [1,2]. The obvious challenge to their growth in bulk single crystalline shape
imposed by their high melting point is rendered more difficult by series of structural phase
transitions occurring upon cooling from the melting point. For instance, Eu2O3 exhibits no less than
four phase transitions and Gd2O3 three of them between room and melting temperatures [3]. The
case of Tb2O3, which exhibits a melting point of 2410°C, turns out to be complicated by its mixed
valence character which results in an easy oxidation at intermediate and high temperatures. These
various Tb3+/Tb4+ cationic equilibria lead to different magnetic phase transitions, as measured in
TbO2, TbO1.823, Tb11O20, Tb4O7 and Tb7O12. To the best of our knowledge, the crystal growth of
cubic pure Tb2O3 crystals has never been achieved nor reported. In this work, we present the first
crystal growth of cubic Tb2O3 single crystals by a hydrogen free and controlled atmosphere flux
method which uses a heavy metal free solvent working between 1235°C and 1160°C, that is, at less
than half the melting temperature of this sesquioxide. Cubic millimeter-sized crystals extracted
from as-grown boules are phase (powder XRD) and chemically (GDMS) pure and exhibit a Verdet
constant which is at least three times higher than that of a commercial Tb3Ga5O12 (TGG) crystal, in
the visible and near-infrared spectral ranges. The 1.36 mm thick crystals display a transmission
coefficient higher than 77% over the 525 nm–1.38 μm spectral range, which corresponds to an
absorption coefficient of 0.17 cm-1 at 1064 nm. The absorption spectrum, magnetic susceptibility
and specific heat measurements on the single crystals confirm the absence of any detectable Tb4+
cations and other impurities. Thus, our growth process was found to remarkably stabilize the Tb3+
oxidation state in Tb2O3 without resorting to any post-growth thermal treatment and the first Verdet
constant measurements in the NIR spectral range suggest that these crystals have great potential as
Faraday rotators as compared to well-known TGG crystal. Emission spectra recorded at room
temperature and 10 K, coupled with crystal field analysis will provide beginnings of an explanation
for this remarkable property.
References:
[1] Ph. Veber, M. Velázquez, V. Jubera, S. Pechev, O. Viraphong, CrystEngComm. 13 (16) (2011)
5220.
[2] Ph. Veber, M. Velázquez, G. Gadret, D. Rytz, M. Peltz, R. Decourt, CrystEngComm, 17 (3)
(2015) 492.
[3] M. Foex, J.-P. Traverse, Rev. Int. Hautes Temp. Refract., 3 (1966) 429.
POSTER
S11-P02
Growth of p-Type ZnOS Films by Pulsed Laser Deposition
Kenkichiro Kobayashi*1, Tohru Ohtsuki1, Yasumasa Tomita1, Yosiumi Kohno1,
Yasuhisa Maeda1, and Shigenori Matsushima2
1
Shizuoka University, 3-5-1, Johoku, Hamamatsu (Japan)
Kitakyushu National College of Technology, 5-20-2, Shii, Kitakyushu (Japan)
2
Transmittance / %
White light-emitting diodes (LED) have been developed by using Ga1-xInxN-based blue LEDs
and yellow phosphors. From viewpoints of resources and cost, the substitutes for Ga and In atoms
are required. ZnO is one of promising substitutes because of its abundant raw materials and nontoxicity. In recent, the strong bowing effect of the valence band was found in ZnO1-xSx (ZnOS)
films. In the range of 0<x<0.5, the top of the valence band of ZnOS is moved upward with the
sulfur-content. In the present work, we have prepared ZnOS films by pulsed laser deposition
(PLD), and clarify the optical and electrical properties of the obtained ZnOS films.
ZnOS films were deposited on quartz and Si substrates by PLD with a KrF excimer laser with
200 mJ and a repetition rate of 10 Hz. Targets were undoped ZnO and S-doped ZnO which were
prepared by sulfurizing the ZnO target in S-atmospheres. For doping of excess S atoms into a film,
vacuum-evaporation of S was also simultaneously carried out during the film-growth by PLD. The
film growth was performed at 1-10 Pa. The thicknesses of the films were ca. 500 nm. Carrier types
of films were determined by the Seebeck-effect measurements.
For ZnOS films prepared from S-doped ZnO targets, the c-axis lengths of the films increase
with increasing S-content in the target. Using the Vegard's law, the S-content is estimated to be in
the range of 0.05 to 0.1. The ZnOS films exhibit a distinct absorption at wavelengths < 500 nm.
Optical band gap of the ZnOS films is reduced to 3.0 eV. All of the ZnOS films are n-type,
irrespective of S-contents. To suppress the generation of oxygen vacancies in a film, excess S
atoms are incorporated into a film by simultaneous S-evaporation in PLD process. Figure 1 (left)
shows X-ray diffraction patterns of ZnOS films prepared by PLD accompanying simultaneous Sevaporation. As a sublimation temperature of S increases, the diffraction peaks shift toward lower
values. The S-contents in the ZnOS films are estimated to be in the range of 0.14 to 0.30. Figure 1
(right) shows transmission spectra of the ZnOS films. The absorption is seen in visible region <
600 nm. The absorption in the visible region is due to a decrease in the band gap. The resistivity of
the ZnOS films increases with the S-sublimation temperature. It should be noted that the ZnOS
film (S=0.3) exhibits the hole-conductivity. The appearance of the hole-conductivity may be
achieved by the incorporation of acceptors of interstitial S atoms or Zn vacancies, which are
produced by the simultaneous S-evaporation.
Intensity / arb. unit
60 °C
62 °C
64 °C
66 °C
68 °C
70 °C
25
30
35
2 / degree
40
45
100
80
60
60 °C
62 °C
64 °C
66 °C
68 °C
70 °C
40
20
0
200
400
600
800
Wavelength / nm
1000
Figure 1. X-ray diffraction patterns of ZnOS films(left) and their transmission
spectra (right)as a function of S-sublimation temperatures in PLD processes.
S11-P04
On the crystal growth, characterization and magnetic properties of two new
phases discovered in the PbO-Fe2O3-P2O5 system
Matias Velázquez*,1, Hassan El Hafid1, Olivier Pérez2, Abdelaziz El Jazouli3, Alain Pautrat2,
Rodolphe Decourt1, Philippe Veber1, Oudomsack Viraphong1 and Claude Delmas1
1
CNRS, Université de Bordeaux, ICMCB, 87 avenue du Dr. A. Schweitzer, 33608 Pessac cedex (France)
Laboratoire de Cristallographie et Sciences des Matériaux, UMR 6508 CNRS/Université de Caen, 6 Boulevard du
Maréchal Juin, 14050 Caen cedex 04 (France)
3
Laboratoire de Chimie des Matériaux Solides, URAC 17, Université Hassan II Mohammedia, Faculté des Sciences
Ben M’Sik, Casablanca (Morroco)
E-mail: [email protected]
2
A new oxyphosphate compound PbFe3O(PO4)3 has been discovered and grown in single
crystalline shape by a combination of Bridgman and self-flux methods. Its crystal structure was
characterized by single crystal X-ray diffraction (XRD) between 293 and 973 K (monoclinic
symmetry P 21/m, a=7.5826 Å, b=6.3759 Å, c=10.4245 Å and =99.956°, Z=2, at room
temperature) [1]. DC magnetic susceptibility and specific heat measurements performed on single
crystals unveiled an unusual sequence of second order ferromagnetic-like phase transitions at
Tc1=31.8 K, Tc2=23.4 K and Tc3~10 K. AC magnetic susceptibility suggests a glassy-like dynamics
between ~20 K and Tc3. The magnetic behaviour of this new compound may open a possibility to
test spin-glass/FM or AFM coexistence theories with real systems of localized S=5/2 spins in a
virtually non disordered phase [1,3]. The closeness of the three ferromagnetic-like magnetic phase
transitions observed for the first time on single crystalline samples, may offer an opportunity to
investigate the vicinity of multicritical points in « T-J0 » phase diagrams in fixed 0H field. The
exact nature of the successive magnetic phases at low temperature has to be firmly established by
elastic and inelastic neutron diffusion. The observed critical mean-field behaviour must also be
confirmed (universality class, possible crossovers) on well oriented single crystals with an
optimized demagnetizing field factor [1,2]. Further exploration of the PbO-Fe2O3-P2O5 system led
to the discovery of a new langbeinite phase, Pb1,5Fe2(PO4)3, the crystal structure of which was
solved by room temperature single crystal XRD (P213, Z=4, a=9,7831(2) Å). This phase does not
undergo any structural phase transition down to 6 K nor any kind of long range ordering down to 2
K, as found by specific heat and magnetic susceptibility measurements. Our investigations show
that directional solidification of high-temperature solutions can be an interesting tool for
exploratory crystal growth research.
References
[1] Hassan El Hafid, Matias Velázquez, Olivier Pérez, Abdelaziz El Jazouli, Alain Pautrat,
Rodolphe Decourt, Philippe Veber, Oudomsack Viraphong and Claude Delmas, Eur. J. Inorg.
Chem, 36, 5486 (2011).
[2] Hassan El Hafid, Matias Velázquez, Olivier Pérez, Abdelaziz El Jazouli, Alain Pautrat,
Rodolphe Decourt, Emmanuel Véron, Oudomsack Viraphong and Claude Delmas, J. Sol. St.
Chem., 202 (2013) 85-92.
[3] Hassan El Hafid, Matias Velázquez, Abdelaziz El Jazouli, Alain Wattiaux, Dany Carlier,
Rodolphe Decourt, Michel Couzi, Philippe Goldner and Claude Delmas, Solid State Sciences, 36
(2014) 52-61.
S11-P05
Synthesis and structure of perovskite organic-inorganic hybrid of
[NH3(CH2)4NH3CoCl4] 1,4 butane diammonium tetrachlorocobaltate
Seham Kamal. Abdel-Aal
Teaching assistant, Physics Department, Faculty of Science, Cairo University, Egypt.
Correspondence e-mail: [email protected]
A new organic-inorganic hybrid [NH3(CH2)4NH3]CoCl4, 1,4 butane diammonium tetra-chlorocobaltate has
been synthesized and characterized by single crystal X-ray diffraction, The hybrid crystallize in a triclinic
system, space group P1̄, with the unit cell parameters a=7.2869 (2) Å, b = 8.1506 (2)Å, c = 10.4127 (3)Å, α =
77.2950 (12)°, β = 80.0588 (11)°, γ = 82.8373 (12)° and Z=2. The final R factor is 0.064. The structure
consists of organic dications [NH3(CH2)4NH3]+2 in a zigzag structure and inorganic dianions CoII ion
coordinated by four Cl atoms in a isolated tetrahedral structure [CoCl4]-2. The organic and inorganic layers
connected with each other through N-H….Cl hydrogen bonds.
S11-P07
Macro- and microcrystallization of rare-earth aluminum borates in
multicomponent systems RAl3(BO3)4 - K2Mo3O10 - B2O3 - R2O3 (R = Y, Gd, Lu)
D.A. Naprasnikov 1*, V.V. Maltsev 1, N.I. Leonyuk 1, K.N. Gorbachenya 2
1
Department of Crystallography and Crystal Chemistry, Geological Faculty, MSU, Moscow (Russia)
2
Belarusian National Technical University, Minsk (Belarus)
Crystals of rare-earth aluminum borates RAl3(BO3)4 (R=Y or lanthanide) belong to the structural
type of carbonate mineral huntite CaMg3(CO3)4, and they are the subjects of extensive studies due
to their promising nonlinear optical and laser properties [1]. Therefore, investigations of micro- and
nanocrystallization in viscous glass-forming borates melts is also one of the priorities on the way
for searching relatively inexpensive optical glass-ceramic composites as alternative components of
compact laser systems [2,3].
In this paper, LuAl3(BO3)4 (LuAB) crystals up to 4 mm were grown from high-temperature
solutions using K2Mo3O10 based fluxes in the temperature range of 1125-900oC. The most highquality samples were obtained in the case of complex flux containing 30-40 mol.% K2Mo3O10 - 5040 mol.% B2O3 - 20 mol.% Lu2O3. X-ray diffraction patterns of the crystals grown are similar to
those for other borate of huntite family available in the ICSD database. Spectroscopic properties of
LuAB crystals doped with active ions are comparable with the same characteristics of GdAl3(BO3)4
(GdAB) crystals as it has been demonstrated earlier [3].
Glass-ceramic materials based on YAl3(BO3)4 (YAB) and GdAB were synthesized in a wide
temperature range. Upon quenching melts of YAB and GdAB stoichiometries, opaque glass
ceramic (glaze) is formed, and it becomes transparent with 100% excess of boric anhydride and
prolonged exposure at elevated temperature (1250 and 1350oС for GdAB and YAB, respectively).
The samples obtained are characterized by two types of X-ray diffraction patterns: (1) typical for
amorphous material and (2) with well-defined reflections, indicating the presence of crystalline
phase in a glassy matrix. As a rule, they coincide with X-ray spectra of GdAB and YAB crystals.
The electron microscope images of YAB-containing glazes demonstrate cavities, most likely,
associated with the removal of volatile components during crystallization process. According to
microprobe analysis, there are areas of different composition in glass matrix that could also indicate
the formation of nano-sized crystallites. In the transparent GdAB-composites needle microcrystals
detected, while there are two types of micro-crystals in the glaze: elongated individes (up to several
microns) with a ratio of length to width about 10/1 and idiomorphic prismatic ones. Using the X-ray
microtomography method, it was found that crystalline phase content in selected volume (1 mm3) of
glass matrix is up to 32.5%, while the content of cavities corresponds to 0.35%. The absorption
spectra measured for (Er,Yb):YAB-containing glass-ceramic are comparable with the spectra of Er
and Yb co-doped functional phosphate glasses.
References:
[1] Ballman A.A., Amer. Mineral., 47 (1962) 1380
[2] G. Karlsson et al., Appl. Phys., B 75 (2002) 41
[3] Gorbachenya K.N. et al., Optics Letters, 38(14) (2013) 2446
S11-P09
Structural Characterization of Cobalt Oxide Core-Shell Nanostructure
Lukić-Petrović Svetlana*1, Tadić Marin 2, Petrović Dragoslav1, Štrbac Goran1, Ivetić Tamara1
1
Department of Physics, Faculty of Sciences, University of Novi Sad, Trg Dositeja Obradovića 4, Novi Sad (Serbia)
2
Condensed Matter Physics Laboratory, Vinča Institute, University of Belgrade, P.O. Box 522, Belgrade (Serbia)
Spinel-type cobalt oxide (Co3O4) is a p-type semiconductor with an energy gap of 1.41.8 eV
and antiferromagnetic properties [1], but when in the form of nanoparticles, shows ferromagneticlike properties at room temperature [2]. Co3O4 nanoparticles in silica matrix were synthesized using
utilizing sol-gel combustion (SGC) method. The crystalline structure and morphology were
investigated in detail using X-ray diffraction (XRD), Raman spectroscopy and scanning electron
microscopy (SEM). Characteristic Raman-active modes for normal spinel cubic Co3O4 were
observed. The individual Raman band position, relative intensity and FWHM parameter were
determined by Lorentz line shape peak fitting (Figure 1). The average crystallite size was calculated
to be approximately 9 nm from the obtained XRD data and using the Scherrer relation, while SEM
images that were taken at astonishing magnifications up to 300,000 also pointed to well crystallized
core-shell Co3O4/SiO2 nanostructure.
Figure 1. As-synthesized Co3O4/SiO2 nanostructure: (a) XRD pattern and (b) fitted to Lorentz line
shape Raman spectrum (black dots-experimental points, straight red line-fitted), and its SEM
images.
Acknowledgments: Bilateral cooperation between the Republic of Serbia and the Republic of Slovenia,
APV Provincial Secretariat for Science and Technological Development and Ministry of Education, Science
and Technological Development of the Republic of Serbia.
References:
[1] Tang C-W., Wang C-B., Chien S-H., Thermochimica Acta, 473 (2008) 68-73.
[2] Tadic M., Panjan M., Markovic D., Stojanovic B., Jovanovic Dj., Milosevic I., Spasojevic V., Journal of
Alloys and Compounds, 586 (2014) S322-S325.
S11-P11
Low Temperature Growth of Cu2ZnSnS4 Thin Films
by Metal Xanthate Precursors
Akiko Mochihara1, 2, Kenji Yoshino1, 2, *, Naoya, Komaki1, Minobu Kawano3, Yuhei Ogomi2, 3,
Qing Shen2, 4, Taro Toyoda2, 4, Shuzi Hayase2, 3
1
1-1 Gakuen Kibanadai-nishi, Miyazaki 889-2192, Japan
2
CREST, Japan Science and Technology Agency (JST), 4-1-8 Honcho, Kawaguchi,
Saitama 332-0012, Japan.
3
Department of Engineering Science, Faculty of Informatics and Engineering,
The University of Electro-Communications, 1-5-1 Chofugaoka, Chofu,
Tokyo 182-8585, Japan.
4
Graduate School of Life Science and Systems Engineering, Kyushu Institute of
Technology, 2-4 Hibikino, Wakamatsu, Kitakyushu 808-0196, Japan
In recent years, the Cu2ZnSnS4 (CZTS) and Cu2ZnSnSe4 (CZTSe) compound semiconductors
are potential alternative materials to CuInGaSe2 (CIGS) for thin film photovoltaic absorber layers.
This is because all of the elements in CZTS and CZTSe are abundant in the earth, and the bandgap
energy is controlled by the ratio of S and Se. Therefore, environmental concerns are eliminated with
these materials, paving the way for gigawatt scale mass production of solar cells. Despite their brief
history in solar cell technology, CZTS, CZTSe, and Cu2ZnSn(S,Se)4 (CZTSSe) solar cell devices
are rapidly advancing in the solar cell markets. For example, CZTSSe solar cells fabricated at IBM
have achieved an efficiency of 11.1% using a hydrazine solution process [1]. Shin et al. have
reported CZTS thin-film solar cell with an efficiency of 8.4% using a vacuum based thermal
evaporation process [2]. Repins et al. have reported CZTSe solar cells with an efficiency of 9.2%
using co-evaporation process [3]. In this work, CZTS thin film on glass substrate is grown by
dipping-coat from Cu-, Zn- and Sn-xanthate solution as precursor materials. The samples are
annealed under nitrogen atmosphere. X-ray diffraction (XRD), electron probe microanalysis
(EPMA), scanning electron microanalysis (SEM), thermoprobe analysis and the four-point probe
method are carried out.
The XRD spectra indicate that a peak of CZTS (112) starts to observe at 150 °C. This
temperature is lowest in non-vacuum process of CZTS film. The all samples indicate chalcopyrite
structure and polycrystalline as evidenced by the XRD spectra. A value of full width at half
maximum of (112) peak increases with increasing temperature. This indicates that an grain size
increases with increasing annealing temperature. The samples are non-uniform composition such as
Cu-poor and Zn-rich at low temperature and become S-poor with increasing temperature. Sulfur
evaporates because vapor pressure of sulfur is high. The all samples are p-type conductivity by
thermo prove analysis because Cu vacancy (VCu) defects is dominant in the samples from EPMA
results. The resistivity increases with the increasing annealing temperature. It is assumed that this
reason is due to decreasing carrier concentration. Donor type defects such as (VS) increases with
increasing the annealing temperature.
References:
[1] T. K. Todorov, J. Tang, S. Bag, O. Gunawan, T. Gokmen, Y. Zhu, and D. B. Mitzi, Adv. Energy Mater.
3 (2013) 34.
[2] B. Shin, O. Gunawan, Y. Zhu, N. A. Bojarczuk, S. J. Chey, and S. Guha, Prog. Photovol: Res. Appl. 21
(2013) 72.
[3] I. Repins, C. Beall, N. Vora, C. DeHart, D. Kuciauskas, P. Dippo, B. To, J. Mann, W. C. Hsu,
A. Goodrich, and R. Noufi, Sol. Energy Mater. Sol. Cells 101 (2012) 154.
S11-P12
Formation of microcrystalline SrB4O7 :Sm2+ dots in SBO glass-ceramic
Głowacki Michał 1*, Martín Inocencio R. 2, Pérez-Rodríguez Carla 2, Berkowski Marek 1
1 Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warsaw (Poland)
2 Departamento de Física, Instituto de Materiales y Nanotecnología (IMN),Universidad de La Laguna, Av. Astrofísico Francisco
Sánchez, s/n E-38206 La Laguna, Tenerife (Spain)
Strontium tetraborate – SrB4O7 (SBO) – is a compound with high mechanical strength, high optical
damage threshold and excellent non linear properties [1]. Doped with lanthanide ions SBO can be used as
visible light emitting material. The oxidation state of dopant ion (thus also the emission spectra) depends on
the form of the obtained material (crystal/glass) as well as on the crystal growth method [2].
This work is aimed to create SBO:Sm, where areas doped with di- and trivalent samarium ions were
spatially distinct. As a result SBO glass with microcrystalline SrB4O7 : Sm2+ dots is presented. Peculiarities of
the formation of the microcrystalline dots on SBO glass and results of structural and optical investigations will
be discussed.
According to [3] in the glass of SBO:Sm one can observe only Sm3+ emission lines, but due to the
crystallization process carried out using 3,5 W Ar laser beam focused in one spot on the surface of the
SBO:Sm glass the emission peaks coming from Sm2+ ions in a crystalline environment can be detected.
Therefore, presence and intensity of Sm2+ luminescence spectral lines became an indicator for microcrystalline
dot formation (Figure 1.).
a)
b)
Figure 1. a) Intensity of Sm2+ emission in SBO microcrystalline dot; b) diffraction spectra of SBO glass and crystalline
sample
Acknowledgements:
The work was funded by the Polish National Science Center (NCN) on the basis of the decision number DEC2013/09/D/ST5/03878
References:
[1]
Yu.S. Oseledchik, A.L. Prosvirnin, V.V. Starshenko, V.V. Osadchuk, A.I. Pisarevsky, S.P. Belokrys, A.S. Korol,
N.V. Svitanko, A.F. Selevich, S.A. Krikunov, J. Cryst. Growth 135 (1994) 373–376
[2]
R. Stefani, A.D. Maia, E.E.S. Teotonio, M.A.F. Monteiro, M.C.F.C. Felinto, H.F. Brito, J. Solid State Chem. 179
(2006) 1086–1092
[3]
P. Mikhail, J. Hulliger, M. Schnieperb, H. Billb, J. Mater. Chem. 10 (2000) 987-991
S11-P13
Form studies and thermodynamic evaluation of Fasoracetam
BRAM, Harmsen
TOM, Leyssens
Institute of Condensed Matter and Nanosciences (IMCN), Laboratory of crystal engineering
Place Louis Pasteur 1. Bte Lavoisier B1.75
Fasoracetam (NS-105) is a research chemical from the racetam family, a cognition
enhancer, designed for treatment of Alzheimer’s disease1. In this study, we performed
a form study of this active pharmaceutical ingredient. Two crystalline forms of
fasoracetam were discovered and subjected to thermal analysis. The forms were
indentified as a stiochiometric fasoracetam hydrate and fasoracetam anhydrate as
confirmed through both XRD and thermal analysis. The stiochiometry observed for the
hydrated fasoracetam was confirmed by TGA.
The anhydrate is stable at ambient conditions after prolonged exposure and does not
undergo a solid-state transition to the hydrated form. DSC curves for both compounds
show a large difference in melting point (57°C hydrated and 92°C anhydrate form), of
which the lower melting point for the hydrate could be attributed to a less favored
crystal lattice due to the presence of water.
References
1. Ogasawara T, Itoh Y, Tamura M, Mushiroi T, Ukai Y, Kise M, Kimura K. Involvement of cholinergic and GABAergic
systems in the reversal of memory disruption by NS-105, a cognition enhancer. Pharmacol Biochem Behav 1999;64:41-52.
S11-P15
Crystal and electronic structure and magnetic properties of Gd7Pd3-xNix
intermetallics
Ewa Talik*1, Adam Guzik1, Monika Oboz1,Joachim Kusz1, Paweł Zajdel1, Maciej Zubko2
1
Institute of Physics, University of Silesia, Uniwersytecka 4, 40-007 Katowice, Poland.
Institute of Materials Science, University of Silesia, ul. 75 Pułku Piechoty 1a, 41-500 Chorzow, Poland.
2
Recently, the single crystals of the Gd7-xYxPd3 series (x = 0–6) were investigated to find the
influence of nonmagnetic yttrium substitution on the hybridization process, magnetic interactions
and magnetic entropy changes [1]. This work presents X-ray diffraction, SEM/EDX, TEM, ac and
dc - magnetic susceptibility and magnetocaloric examinations results of the Th7Fe3-type
Gd7Pd3-xNix series. No structural transformation is observed upon doping with nickel and the unit
cell volume decreases due to difference between radii of Pd and Ni.
The magnetization phenomena are very sensitive to the applied dc magnetic field resulting in
thermomagnetic hysteresis even in the weakest fields. Ni substitution into Pd positions causes the
decrease of the Curie temperature. Just below the TC, the Hopkinson peak is observed due to
competition between local anisotropy and spontaneuos magnetization.
A dispersion of the ac-susceptibility is observed at different frequencies, which vanishes at the
Curie point. In all compounds a magnetic reorientation processes is observed around 150 K. The
maximum entropy is slightly higher for Gd7Pd2Ni in comparison to the parent compound due to
higher disorder in the spin field.
Acknowledgements
This work was partially financed by the Polish National Science Centre (Narodowe Centrum Nauki)
under Grant No. 2011/03/B/ST5/01035.
Pd 4d
Intensity (arb.u.)
Gd 4f
Gd7PdNi2
Gd7Pd3
Gd7Pd2Ni
-0.3
0.3
0.6
Gd 5p
Ni 3d
Gd 5d
0
0
10
20
30
Binding energy (eV)
Figure 1. XPS valence band, Gd4f and Gd5p of the examined compounds. The insert shows the
density of states at the Fermi level.
References:
[1] Talik E., Oboz M., Kusz J., Winiarski A.and Hofmeister W., J. Alloys and Compounds 582
(2014) 718.
S11-P16
New fluorescent hybrid materials in oxyfluoride glass matrix
Olga Petrova, Ilya Taydakov, Maria Anurova, Alina Akkuzina, Roman Avetisov,
Andrew Khomyakov, Igor Avetissov*
D .Mendeleyev University of Chemical Technology of Russia, Miusskaya pl.9, Moscow (Russia)
Hybrid materials (HM) based on metal-organic phosphors and inorganic glasses are promising
materials for creating new light emitting devices [1]. Hybrid materials were synthesized by a high
temperature reaction. The organic phosphors based on Eu and Al complexes which we used to
produce HM’s are presented in the Table. An easy melting 80PbF2-20B2O3 glass was used as a
glassy matrix. HM’s synthesized at 600C during 30 seconds at the melt stirring. The produced
HM’s were yellowish glassy plates. They demonstrated photoluminescence (PL) of varying
intensity in the range of emission colors from red to green when excited by 377 nm diode.
PL spectra of the HM’s based on Eu-complexes had a distinguished line of Eu3+ transition
(max=611 nm), but for the HM’s based on Eu(NTA)3(Bath) and Eu(NTA)3(Phen) (Fig. 1, lines 3
and 4), the intensity of the spectrum short-wave part (=400-580 nm) was more intense.
We have assumed that there is an exchange reaction accompanied by partial decomposition of
organic complexes. At the same time Eu3+ ions migrate into the glass matrix, and this causes the
reduction of PL intensity to the values typical for inorganic glasses doped by Eu3+. Simultaneously,
the ligands are bonding into complexes with Pb [2], and PL of the Pb based complex in the HM
becomes more intense. The Pb-complex formation is confirmed by PL peak's positions which
cannot be attributed to transitions between the levels of the individual ligands. For HM based on
Alq3 (Fig. 1, line 5), PL spectrum corresponds to α-Alq3 [1], i.e the exchange reaction does not take
place. Contrary to solution reactions we developed a synthesis technique for new luminescent
materials by conducting a high-temperature exchange reaction between an inorganic glass matrix
and organic complexes.
The research was supported by the Russian Science Foundation grant № 14-13-01074.
№
Phosphor
Abbreviati
on
4,4,5,5,6,6,7,7,8,8,9,9,9-tridecafluoro1-(1-methyl-1H-pyrazol-4-yl) nonane- Eu(L1)3
1,3- dionato-(1,10-phenanthroline)
(Phen)
europium
4,4,5,5,6,6,6-heptafluoro-1-(1-methylEu(L2)3
2 1H-pyrazol-4-yl)hexane-1,3- dionato(Phen)
(1,10-phenanthroline) europium
Tris(4,4,4-trifluoro-1-(2-naphthyl)
Eu(NTA)3
3 butane-1,3-dionato-(4,7-diphenyl(Bath)
1,10-phenantroline) europium
Tris(4,4,4-trifluoro-1-(2-naphthyl)
Eu(NTA)3
butane-1,3-dionato-(1,104
(Phen)
phenanthroline) europium
1
5
Tris(8-hydroxyquinoline) aluminum
Alq3
Chromaticity
coordinates
CIE
X=0.3476
Y=0.3272
X=0.2938
Y=0.2630
X=0.2592
Y=0.3749
X=0.2054
Y=0.2769
X=0.2708
Y=0.4997
Figure 1. Luminescence spectra of HM (1–5) (figures correspond to the sample numbers in Table).
References:
[1] Petrova O.B. et al. Eur. J. Inorg. Chem. 2015 (2015), №7, 1269–1274
[2] Marandi F. et al. Inorg. Chim. Acta. 363 (2010), 4000–4007
S11-P17
Crystal engineering of molecular salts for single-crystal to single-crystal [2+2]
cycloaddition photoreactions
Spinelli Floriana* 1, d'Agostino Simone1, Braga Dario1, Grepioni Fabrizia1
Dipartimento di Chimica Ciamician,University of Bologna, Bologna (Italy)
1
In the last decades [2+2] cycloaddition photoreactions in the solid state have attracted the
attention of many researchers [1]. As a rule-of-thumb, when the molecular arrangement found in the
crystal packing satisfies the Schmidt’s criterion - i.e. double bonds are parallel and at a separation of
approximately 4.2 Å [2] - efficient and selective reactivity is observed in most cases. Solid-state
reactivity is of great interest, as solvent-free, solid-state processes represent a “green chemistry”
approach to the synthesis of new materials [3].
In this study we report on the single crystal-to-single crystal (SCSC) photoreactivity of molecular
salts of cinnamic acid derivatives. Reactions for such class of compounds have been monitored by
means of polarized light microscopy and single crystal X-ray diffraction. Following the structural
response to UV via single crystal XRD at various irradiation intervals, it has been possible to
conduct a detailed kinetic study directly in the SC medium.
Figure 1. Scheme of a [2+2] photoreaction involving properly aligned olefins in the solid state.
References:
[1] Cohen, M.D. The photochemistry of organic solids. Angew. Chem. Int. Ed. Engl 14 (1975), 386.
[2] (a) M. D. Cohen and G. M. J. Schmidt, J. Chem. Soc., (1964), 2000; (b) G. M. J. Schmidt, Pure Appl.
Chem., 27 (1971), 647.
[3] D. Braga, F. Grepioni, Making Crystal by Design: Methods, Techniques and Applications; Wiley-VCH,
Weinheim (2007).
S11-P18
Crystallization of a New Calcium Bisphosphonate
through Octacalcium Phosphate Digestion
Boanini Elisa*1, Gazzano Massimo2, Bigi Adriana1
1
Department of Chemistry “Giacomo Ciamician”, University of Bologna,
via Selmi 2, 40126 Bologna (Italy)
2
ISOF-CNR, Bologna (Italy)
Bisphosphonates such as Sodium Alendronate are widely recognized as potent inhibitors of
osteoclast activity and clinically used for the treatment of diseases associated with bone loss, such
as osteoporosis, Paget’s disease and osteolytic tumors [1]. On the other hand, the prolonged use of
these drugs was demonstrated to cause over-suppression of bone metabolism leading to
osteonecrosis, especially of the jaw [2]. This drawback stimulated many studies for the
development of strategies for local administration, even in combination with calcium phosphates,
which mimic the structure and chemistry of bone inorganic component [3]. In particular,
Alendronate was previously shown to interact with the Calcium ions of Hydroxyapatite through a
bidentate chelation of deprotonated oxygen atoms [4].
Herein we investigate Octacalcium phosphate, Ca8H2(PO4)6•5H2O (OCP), as an alternative to
Hydroxyapatite for the local administration of Alendronate. The results of the structural,
spectroscopic, and microscopic investigation show that soaking OCP into Alendronate solutions
provokes the deposition of small crystalline rod-shaped formations onto the larger crystals of
calcium phosphate. The amount of Alendronate loaded onto OCP increases as a function of the
Bisphosphonate concentration in solution. Indeed, we demonstrate that Alendronate in solution is
able to recruit Calcium ions from OCP crystals, yielding the quantitative formation of crystalline
Calcium Alendronate monohydrate, CaALH2O (figure 1). At high concentration, Alendronate
craving for Calcium ion causes displacement of Ca2+ from calcium phosphate crystalline structure
which results in the complete digestion of OCP [5].
Figure 1. A view of the CaAL·H2O structure.
References:
[1] Russell R.G.G., Bone, 49 (2011) 2.
[2] Pazianas M., Abrahamsen B., Bone, 49 (2011) 103.
[3] Boanini E., Torricelli P., Gazzano M., Giardino R. Bigi A., Biomaterials, 29 (2008), 790.
[4] Boanini E., Gazzano M., Rubini K., Bigi A., Advanced Materials, 19 (2007) 2499.
[5] Boanini E., Torricelli P., Gazzano M., Fini M., Bigi A., Advanced Materials, 25 (2013) 4605.
S11-P19
X-Ray diffraction and Raman spectroscopy studies of temperature induced
phase transitions in Sr3-xCaxFe2TeO9 (0 ≤x≤ 1) triple perovskite
Abdelhadi Elhachmi 1,*, Bouchaib Manoun 1, P. Lazor 2.
1
Laboratory of materials science, backgrounds and modeling. FP Khouribga, University Hassan 1st, Hay Ezzaitoune
BP 145, Khouribga 25000, Morocco.
2
Department of Earth Sciences, Uppsala University, SE-752 36, Uppsala, Sweden.
*
Corresponding author email: [email protected] Keywords: Double perovskite, Sr3-xCaxFe2TeO9, crustal structure, Phase transition, X-ray diffraction.
The families of materials type A3B2B’O9 (A= Ca, Sr, Ba; B = transition metal and B’ = Mo, W,
Te or U) have recently attracted great attention as ferrimagnets compounds with low or height TC’s,
in some cases, above RT. These compounds are double perovskites with crystallographic formula
could be rewritten as A2B(B1/3B’2/3)O6. They, thus, display an intrinsic partial disordering over half
of the perovskite (B1/3B’2/3) positions. We have prepared different materials with A= Ca, Sr; B= Fe
and B’ = Mo, W, Te or U and by using XRD and Mossbauer spectroscopy we have shown that all
the compounds are tetragonal and can be refined in the space group I4/m [1]. Raman and infrared
spectroscopy provide valuable insight into order-disorder phenomena and are very sensitive to
sample composition and structural variations, making it suitable for studying the effects of atomic
substitutions in complex perovskites [2].
Recently Sr3Fe2TeO9 and Ba3CaNb2O9 complex perovskite have been studied by X-ray
diffraction (XRD) [3] and Raman spectroscopy [4]. At room temperature, the crystal structure of
Sr3Fe2TeO9 is tetragonal [3], s.g. I 4/m, with a = b = 5.5626(5) Å, c = 7.8634(7) Å.
In the present work, using X-ray diffraction and Raman spectroscopy techniques, we report that
Sr3-xCaxFe2TeO9 have a tetragonal symmetry with I4/m as space group at RT. Furthermore,
increasing temperature for this compound, remarkable change in the temperature dependence of the
Raman modes are illustrated, leading to high temperature induced phase transitions.
References:
[1] M. C. Viola, M. S. Ausburger, R.M. Pinnaca, J. C. Pedregosa, R. E. Carbonio and R. C.
Mercader,J. Solid State Chem., (2003) 175, 252.
[2] A. Dias, R. G. Sá, and R. L. Moreira,J. Raman Spectrosc. 39, 1805 (2008).
[3] S.A. Ivanov, P. Nordblad, S.-G. Eriksson, R. Tellgren, H. Rundlo.42 (2007) 776–78
[4] Joa ˜o Elias Figueiredo Soares Rodrigues, Edvan Moreirab, De´bora Morais Bezerra,
Adeilton Pereira Macielc, Carlos William de Araujo Paschoal, (2013) 48- 3298 –3303.
S11-P20
GROWTH AND STRUCTURE OF SINGLE CRYSTAL Ba3TaFe3Si2O14 -LANGASITE
FAMILY MULTIFERROICS.
A.P.. Dudka and A.M. Balbashov *
The Institute of crystallography RAS, Moscow, Russia, * Moscow Power Engineering Institute. email : dudka @ ns.crys.ras.ru
By floating zone melting method on the equipment of URN-2-ZP [1] are grown single crystals
Ba3TaFe3Si2 O14 (BTFS). BTFS belongs to the family of langasite (space gr. P 321 [2], [3]), it
contains magnetic ions Fe3+, shows the magnetic ordering, and is promising multiferroic [4], [5], [6]
. Iron contained langasites are grown at the control pressure of oxygen above the melt within 1-30
atm. and annealing during crystal growing process at a temperature of about1000 oC and smooth
temperature decreasing for 5 h. Speed growth was 7-10 mm/h at rotation of crystal 40 rpm. and feed
rod-1rpm. For ensure a smooth polycrystalline feed rod melting at
growing of single crystal feed rod preliminary was remelted by
floating zone at speed 35 mm/hour in the air. On [7] was made
precision x-ray analysis of BTFS crystal structure using repeated high
resolution data sets at 295K and 95K (ICSD 429640, 429641). Quality
of single crystal is confirmed by criteria of structure refinement
models: at 295K - R / wR = 1.02/ 1.23% for 4552 independent
reflections; at 95 K- R / wR = 1.01- 1.14% for 4501 reflections.
Asymmetry of disordering of atomic positions of magnetic Fe ion in position (3f) and Ba cation in
position (3e) was identified. At cooling atoms of Ba(3e) and Fe(3f) move on the double axis of
symmetry in opposite directions, and Si(2d) shifts on triple axis (i.e. changing the 3 parameters
from 10 possible). In BTFS pronounced helicoidal screwing of electron density along the c axis of
the crystal [8], the axis of the helix runs through the atom Ta(1a). Fixed helix is a structural basis
for magnetic ordering in BTFS.
[1] . A.M. Balbashov, S.K. Egorov.,. J. Cryst. Growth. 1981. V. 52. P. 498.
[2] . E. l. Belokoneva and . N.V. Belov, Dokl. Akad. Nauk USSR, 260 (6), 1363 (1981).
[3] B.V. Mill`., Yu. V. Pisarevsky. Proc. IEEE/EIA 2000 Intern. Frequency Control Symp., Kansas City,
Missouri, USA. P. 133.
[4] . V.Yu. Ivanov., A.A., Mukhin, A.S Prokhorov. B.V. Mill`. Solid State Phenomena. 2009. V, 152-153. P.
299.
[5] . K. Marty ., P. V. Bordet Simonet,. et al. Phys. Rev. b. 2010. V. 81. 054416.
[6] . I.S. Lyubutin., P.G.Naumov, B.V. Mill`. et al. . Phys. Rev. B. 2011. V. 84.214425.
[7] . A.P. Dudka., J. Appl. Cryst. 2007. V. 40. P. 602.
[8] . A. P. Dudka and B. V. Mill ', Crystallogr. Rep. 59 (5), 759 (2014).
S11-P22
Large GaPd2 single crystals grown by the Czochralski technique
Schwerin Judith*1, Müller Dirk1, Burkhardt2 Ulrich, Simon Paul2, Grin Yuri2, Gille Peter1
1
Ludwig-Maximilians-Universität München, Department of Earth and Environmental Sciences, Crystallography
Section, Theresienstr.41, 80333 München (Germany)
2
Max-Planck-Institut für Chemische Physik fester Stoffe, Nöthnitzer Straße 40, 01187 Dresden (Germany)
The intermetallic compound GaPd2 (Co2Si structure type, space group Pnma [1]) shows
excellent catalytic properties like a high selectivity and long-term stability. Because of these
outstanding characteristics this binary compound can be used as a highly active heterogeneous
catalyst in the semi-hydrogenation of acetylene [2]. Although single crystals are not used in
technical application for catalysis, they are necessary to understand the basic catalytic processes.
Many techniques in surface science require large (cm3) single crystals to study the substances´
intrinsic properties. Single crystals of GaPd2 were grown by the Czochralski technique from Ga-rich
off-stoichiometric solutions. An insufficient material transport of the Ga excess next to the growth
interface may lead to mother liquid inclusions in the grown crystal but the use of extremely low
pulling rates (0.025 mm/h) and higher-temperature regions of liquidus balance better the materials
transport to the growth interface.
GaPd2 is characterized by a broad stability region with a retrograde solubility of the Ga excess
component [3]. This leads to supersaturation of the Ga component during post-growth cooling and
is the driving force for precipitation of the orthorhombic phase Ga3Pd5 (Ge5Rh3 structure type,
space group Pbam [4]). In a GaPd2 crystal grown in [001] direction this mechanism has been
observed as two-phase region of GaPd2 and Ga3Pd5 which are ordered in alternate lamellas (2-6
µm) perpendicular to the growth direction. This is the in-situ observation of the formation of the
intergrowth structures predicted previously [5].
Diffraction Laue back–scattering images show a coherent ordering of the two-phase lamellas.
The change of the growth direction of the GaPd2 crystals changes the orientation of the lamellas
keeping the coherent intergrowth unchanged. EPMA measurements have shown different stages of
decomposition of these lamellas from Pd2-xGa1-x to entirely decomposed Ga3Pd5. The total
decomposition to Ga3Pd5 under certain conditions was confirmed by annealing experiments.
Because of growth temperatures much higher than the peritectic one of Ga3Pd5 (~ 1030°C [3]),
primary crystallization of Ga3Pd5 from the liquid solution can be excluded [6].
High-resolution TEM measurements confirm these conclusions on atomic level. Lamellas of
both phases a few nm thick exist, which cannot be resolved by EPMA. The two phases have a
shared interface unit cell with (001)GaPd2  (010)Ga3Pd5 with a lattice parameter misfit < 1%.
Stacking faults and smooth transition between the two phases was observed in the transition area.
These results suggest that the phase separation occurs due to the concentration variation during the
crystal growth.
References:
[1] Kovnir, K., Schmidt, B., Waurisch, C., Armbrüster, M., Prots, Yu., Grin, Yu. Z. Kristallogr. NCS 223
(2008) 7-8.
[2] Armbrüster, M., Kovnir, K., Behrens, M., Teschner, D., Grin, Yu., Schlögl, R., J. Am. Chem. Soc. 132
(2010) 14745-14747.
[3] Okamoto, H., J. Phase Equilibr. Diffus. 29 (2008) 466-467.
[4] Schubert K., Breimer, H., Gohle, R., Lukas, H.L., Meissner, H.G., Stolz, E., Naturwissenschaften 45
(1958) 360-361.
[5] Grin, Yu. In: Modern Perspectives in Inorganic Crystal Chemistry. Kluver AP, (1992), p. 77.
[6] Schwerin, J., Müller, D., Kiese, S., Gille, P., J. Cryst. Growth (2014) 613-616.
S11-P23
Synthesis and crystal growth of NdAl3(BO3)4 with different polytypic structures
E.A. Volkova*, V.V. Maltsev, N.I. Leonyuk
Department of Crystallography and Crystal Chemistry, Geological Faculty, MSU, Moscow (Russia)
Borates RM3(BO3)4 (R = Y or rare earth metal, M = Al, Ga, Cr, Fe, Sc) with huntite
derivative crystal structures are well known multifunctional materials. Among others, NdAl3(BO3)4
(NAB) crystals with huntite-like structure (sp. gr. R32) without center of inversion can be used as
self-doubling laser media. The second harmonic generation intensity in these crystals is 6 times
higher than, for example, in wide spread used KH2PO4 (KDP) material. High Nd3+ concentration
(5.43x1021 cm-3) and fluorescence lifetime of the Nd3+ ion 4F3/2 → 4I11/2 transition in NAB crystal at
19 µs allow it to be applied in miniature, high-efficiency source pumped by semiconductor lasers or
LED's, using the 0.8 µm Nd3+ absorption band. CW laser action from this crystal can be also
obtained in the vicinity of 1.3 µm wavelength. The emission cross section in NAB is 2.1 times
higher than, for instance, in Y3Al5O12:Nd3+. Also, considering its extremely high thermal
conductivity of about 12.7 W/m*K [1,2], this implies applications of NAB material in
communication laser systems and integrated optics. For this reason, a number of publications is
devoted to flux growth of NAB single crystals, taking into account its incongruent melting. On the
other hand, as it follows from the literature, this crystal has polytypic structures having the
following space groups, depending on the crystal growth conditions: R32, C2/c, C2 [3], P6/mmm
(P6/m), C2 [4], R32, C2/c and C2 [5]. So far, however, there is no precise data on their phase
transition temperatures, and it is not easy to obtain NAB single crystals of optical quality and
sufficient sizes. So, the major problem which awaits clarification is precise determination of crystal
growth conditions for non-centrosymmetric and centrosymmetric NAB modifications.
The present work is aimed at assessment of optimal experimental conditions for the NAB
crystal growth. At the first stage, sintering procedure in the Nd2O3-Al2O3-B2O3 system was
investigated using XRD measurements for better understanding of NAB mechanisms formation on
this way. NAB powders were obtained by solid-state reaction method. At the second stage, NAB
single crystals were obtained from K2Mo3O10 based flux systems. XRD measurements were used
for phase analysis of the samples sintered. The experimental powder diffraction patterns were
subjected to quantitative phase analysis, in order to identify a ratio of rhombohedral and monoclinic
phases over the NAB specimens. Rietveld refinement method has revealed, at least, two phases,
namely R32 and C2/c in all synthesized samples. In some cases, the third modification C2 was also
observed. The ratio of these phases is strongly depended on the crystallization temperature and
composition of the fluxed melt.
This research was supported in part by the RFBR grant # 14-05-90000-bеl_а.
References:
[1] D. Xue, S. Zhang, J. Phys.: Condens. Mat., 8 (1996) 1949.
[2] O.V. Pilipenko, V.V. Maltsev, N.I. Leonyuk, A.B. Kozlov, A.V. Shestakov. The CIS Conf. on
Crystal
Growth, Ukraine, Kharkov, Oct. 1-5, 2012, Abstr. P57(A2), 155.
[3] E.L. Belokoneva, N.I. Leonyuk, A.V. Pashkova, T.I. Timchenko, Sov. Phys. Crystallogr., 33
(1988) 765.
[4] Y. Ji, J. Liang, Zh. Chen, S. Xie, J. Amer. Ceram. Soc., 74(2) (1991) 444.
[5] G. Wang, M. He, Z. Luo, Mat. Res. Bull., 26 (1991) 1085.
S11-P24
2D transition metal dichalcogenides grown by chloride driven chemical vapor
transport
Celine Barreteau*1, Alberto Ubaldini2, Enrico Giannini1
1
Department of Quantum Matter Physics, University of Geneva, quai E. Ansermet 24, CH-1211 Geneva 4,(Switzerland)
2D transition metal dichalcogenides (TMD) exhibit interesting electronic and opto-electronic
properties. Moreover, these materials crystallize in a layered structure that consists of vertically
stacked layers, held together by weak Van der Waals-like interactions, which make them easily
exfoliated down to atomically thin layers.
Single crystals of TMDs are grown by chemical vapor transport (CVT) with, in most of the
cases, I2 or Br2 as a transport agent. The choice on the transport agent affects the overall quality of
the crystals and is at the origin of defects as observed in TiSe2 [1]. These defects have a direct
influence on electronic structures and electronic properties of the material and the electronic
devices. Going beyond the limits of this technique, thus improving the crystal quality, is possible by
finding new transport agents. This is particularly needed in the presence of “heavy” transition
metals (TM = Hf, Ta, Mo, W). Transition metal chloride precursors prove to be the most suitable
for growing crystals of Mo and Ta [2]. Here we extend the successful use of chlorides to the growth
of WX2 (from WCl6), HfX2 (HfCl4) and ZrX2 (ZrCl4).
For the latter, some previous work [3] and our preliminary results showed the crucial role of the
stoichiometry on the crystal structure and the morphology. This can be tuned by using the chloride
as a transport agent. We will discuss the relevance of using chlorides for these compounds in order
to grow large and highly pure layered single crystals of each chalcogenide. The possibility of
making electronic devices for some of these crystals has been demonstrated [3].
References:
[1] Hildebrand B., Didiot C., Novello A.M., Monney G., Scarfato A., Ubaldini A., Berger H., Bowler D.R.,
Renner, C., Aebi P., Physical Review Letters, 112 (2014) 197001.
[2] Ubaldini A., Jacimovic J., Ubrig N., Giannini E., Crystal Growth and Design, 13 (2013) 4453.
[3] Gleizes A., Jeannin Y., Journal of Solid State Chemistry, 1 (1970) 180.
[4] Guitiierrez-Lezama I., Arora A., Ubaldini A., Barreteau C., Giannini E., Potemski M., Morpurgo A.,
Nano Letters, 15 (2015) 2336.
S11-P26
Influence of polyols on the formation of nanocrystalline nickel ferrite inside
silica matrices
Marcela Stoia1, Paul Barvinschi2, Lucian Barbu – Tudoran3, Octavian Madalin Bunoiu*2
1
University Politehnica Timisoara, Research Institute for Renewable Energy, P-ta Victoriei No.2,
300006 Timisoara (Romania)
2
West University of Timisoara, Faculty of Physics, Bv. V. Parvan, No. 4, Timisoara 300223 ( Romania)
3
Babes-Bolyai University, 5-7 Clinicilor Street, 400006 Cluj-Napoca (Romania)
Thermal decomposition of metal-organic precursors is one of the most succesfull methods used
for the synthesis of ferrite/silica nanocomposites [1,2]. For the synthesis of nickel ferrite/silica
nanocomposites, we have used a modified sol-gel method that combines the sol-gel processing with
the thermal decomposition of metal-organic precursors, leading to a homogenous dispersion of
ferrite nanoparticles within the silica matrix and a narrow size distribution. We used as starting
materials tetra(ethoxy)silane (TEOS) as source of silica, Fe(III) and Ni(II) nitrates as source of
metal cations and polyols as reducing agent (poly(vynyl alcohol), 1,4-butanediol and their mixture).
The polyol interacts during gelation with TEOS leading to hybrid gels, while during the heating of
the gels it reacts as reducing agent with the nitrates ions, and gets oxidized to carboxylic acids that
form with the metal cations the corresponding carboxylates [2, 3]. FT-IR spectroscopy evidenced
the formation of metal carboxylates inside the silica-gels and the interaction of the polyols with the
Si-OH groups of the polysiloxane network. The formation of precursors as well as their thermal
decomposition during heating was also investigated by TG/DTA coupled technique. X-ray
diffractometry evidenced that in case of nanocomposites with one polyol, nickel ferrite forms as
single crystalline phase inside the amorphous silica matrix, while in case of the mixture of polyols
nickel oxide appears as secondary phase. TEM microscopy evidenced the fine nature of the
obtained nickel ferrite nanoparticles, homogenously dispersed within the silica matrix. Ferrite
nanoparticle size, as determined from TEM images, was in agreement with the crystallite size
estimated from XRD data, leading to the conclusion that the obtained nickel ferrite nanoparticles
are monocrystalline. The elemental maps evidenced that the obtained ferrite nanoparticles are
homogenously dispersed inside the silica matrix. The magnetic properties of the obtained
NiFe2O4/SiO2 nanocomposites depends on the nature of the organics used in synthesis, due to the
modified morphology of both silica gel and nickel ferrite nanoparticles.
Thermal behavior of the precursors and the final nanocomposites was studied using a 1500
MOM Budapest derivatograph. The heating was achieved in static air, in the range 25 – 500 °C,
with a heating rate of 10 °C min-1, on Pt plates using α-Al2O3 as inert material. The synthesized
powders were characterized by FT-IR spectroscopy with a Shimadzu Prestige FT-IR spectrometer,
in KBr pellets, in the range 400 - 4000 cm-1, in air. Phase analysis was achieved with D8 Advance Bruker AXS diffractometer, using the MoKα radiation (λ = 0.7093 Å). SEM images have been
recorded on a Quanta 3D FEG (FEI) microscope. TEM images were recorded on a Jeol-Jem 1010
Microscope. The magnetic investigations on the powders in the as-prepared state were carried out at
room temperature under AC (50 Hz) applied magnetic fields of amplitudes up to 160 kA/m.
References:
[1] Shen X., Zhou Z., Song F., Meng X., J. Sol-Gel Sci. Technol., 53 (2010) 405.
[2] Stoia M., Barvinschi P., Barbu-Tudoran L., J. Therm. Analysis Calorim., 113 (2013) 21.
[3] Stefanescu M., Stoia M., Stefanescu O., Barvinschi P., J. Therm. Analysis Calorim., 99 (2010) 459.
S11-P28
Optical and Structural properties of Cobalt doped Zinc Sulphide (ZnS)/α-Fe2O3
nanoparticles.
Patij K. Shah. Hozefa J. Tinwala , Kirit S. Siddhapara, Dimple V. Shah
1
Applied Physics Department, S. V. National Institute of Technology, Surat-395007, India
email:[email protected]
Optical and structural properties of Cobalt doped ZnS/α-Fe2O3 synthesized by Sol-Gel Method has
been investigated. From X-Ray Diffraction (XRD) results phase of Cobalt doped ZnS/α- Fe2O3 have been
observed. Energy Dispersive Spectroscopy (EDS) analysis confirms that the chemical composition is equal
to the stoichoimetric composition of sample. Morphology and particle size has been observed using
Scanning Electron Microscopy (SEM). Optical properties of Cobalt doped ZnS/α-Fe2O3 have been
investigated using Photo-Luminescence (PL) and UV-Visible Spectroscopy.
S11-P29
THERMOLUMINESCENT PROPERTIES OF POLYCRYSTALLINE CARBON
DOPED LANTHANUM ALUMINATE (LAALO3:C) GROWN BY DIFFERENT
SOLID STATE REACTIONS
Alves Neriene1, Barbosa Ferraz Wilmar2, Oliveira de Faria Luiz*3
1
Universidade Federal de Minas Gerais, Av. Antônio Carlos 6627, Belo Horizonte (Brazil)
Centro de Desenvolvimento da Tecnologia Nuclear, Av. Antônio Carlos 6627, Belo Horizonte (Brazil)
3
Centro de Desenvolvimento da Tecnologia Nuclear and Universidade Feral de Minas Gerais, Av. Antônio Carlos
6627, Belo Horizonte (Brazil)
2
Among several potential application, Lanthanum aluminate (LaAlO3) polycrystals have attracted much
attention for use in gas sensors and as catalyst for oxidative coupling of methane and hydrogenation and
hydrogenolysis of hydrocarbons. Due to their excellent chemical and thermal stability they have been widely
used as a substrate of high-temperature superconductor [1].
Recently, LaAlO3 single crystals, co-doped with Ce3+ and Dy3+ rare earth trivalent ions and grown under
hydrothermal conditions, have been reported to show high thermoluminescent response (TL) when exposed
to low levels of ultraviolet radiation (UVR). However, undoped LaAlO3 synthesized by solid state reaction
method from the 1:1 mixture of aluminum and lanthanum oxide under reducing atmosphere revealed to have
still higher thermoluminescent sensitivity to UV photon fields [2]. On the other hand, it is well known that
the dopping of alfa-Al2O3 single crystals with carbon atoms has produced one of the best TL crystals
commercially available [3]. Thus, we conducted three different syntheses of LaAlO3 by this solid state
reaction method, doping the mixture with carbon, aiming the improvement of its TL response. The
lanthanum aluminate polycrystals were synthesized from the 1:1 mixture of aluminum and lanthanum oxide,
adding 0.1% carbon and annealed at 1700 ° C for two hours in hydrogen atmosphere. The X-ray diffraction
analysis revealed the nucleation of rhombohedral LaAlO3 crystallographic phase, however a small
percentage (15%) of Al2O3 has been also identified in all compositions. One of them presented also peaks
assigned for lanthanum hydroxide, about seventeen percent (17%), which are better presented in the
diffractograms in Figure 1(a). The UV irradiations were carried out using a commercial 8W UV lamp. TL
output measurements were performed at a Harshaw 4500 TL reader. TL curves in Figure 1(b) shows that all
compositions investigated have high TL sensitivity to UVR with also different intensities between
themselves. In this work we discuss the TL output, its linear fitting with UV exposure and the annealing
features for samples obtained using three different combinations of Al2O3, La2O3 and carbon atoms during
the syntheses process.
La2O3:C+Al2O3
(a)
La2O3:C+Al2O3
Al2O3:C+La2O3
La2O3+Al2O3+ C
Al2O3:C+La2O3
La2O3+Al2O3+ C
15
Intensity (a.u)
TL Intensity (a.u)
(b)
10
5
0
10
20
30
40
50
60
2
70
80
50
100
150
200
250
300
Temperature (°C)
Figure 1.(a) XRD patterns for the LaAlO3:C grown by different synthesis. ( ● ) assigned to rhombohedral
phase Lanthanum aluminate (LaAlO3), (■) assigned for lanthanum hydroxide (La(OH)3) and (┼) for Aluminum oxide (Al2O3).
The others peaks with less intensity are assigned for LaAl11O18, a secondary phase of Lanthanum aluminate and (b) TL curves.
References:
[1]
Kaur, J. et al. p. 1-35, 2013/03/23 2013. ISSN 0922-6168. available in:
http://dx.doi.org/10.1007/s11164-013-1126-z .
[2]
[3]
Alves, N. et al. Radiation Measurements, v. 46, n. 71, p. 90-94, 2011. ISSN 1350-4487. available in:
http://dx.doi.org/10.1016/j.radmeas.2014.02.008.
McKeever, S. W. S. et al. Radiation Protection Dosimetry, v. 84, n. 1-4, p. 163-168, 1999.
available in: http://www.scopus.com/inward/record.url?eid=2-s2.00032766479&partnerID=40&md5=95317c6ce5f8b7293f3fdfae09ea6a80 >.
S11-P31
Growth and stability of pinacol hydrates
Szymon Sobczak*, Andrzej Katrusiak
1
Faculty of Chemistry, Adam Mickiewicz University, Umultowska 89b, 61-614 Poznań, Poland
The formation of hydrates of organic and inorganic compounds is widely studied due to the importance
of such materials for their applications in pharmaceutical industry [1]. Hydration can significantly change the
stability and properties of chemicals, for example the solubility and bio-accessibility of active pharmaceutical
ingredients (API’s) [2]. It is known that the hydration can be changed by temperature and concentration of
components, however little is known about the effects of pressure. It was shown that high-pressure
recrystallization can efficiently change the preference both for precipitation of hydrates and anhydrates. For
example, two hydrates of thiourea can be obtained at high pressure; monohydrate (NH2)2CS·H2O above 0.60
GPa and 3(NH2)2CS·2H2O at 0.70 GPa [3]. It was also shown that above 1.20 GPa anhydrous thiourea
becomes stable again. Presently we report the effect of pressure for the recrystallization of a well-known
organic substrate pinacol. This 2,3-dimethyl-2,3-butandiol has been thoroughly studied as a function of
temperature. Several crystalline forms of pinacolone has been characterized by X-rays diffraction [4]: the
anhydrous (monoclinic, C2/c), hemihydrate (hexagonal P6522), monohydrate (monoclinic P2/n) and a
hexahydrate (tetragonal P42/mnm). We have performed in situ high-pressure crystallizations of pinacol in a
diamond-anvil cell (DAC) [5].
Figure 1. In situ single crystal growth of pinacolone (a) anhydrous and (b) hexahydrate
References:
[1] Blagden N., de Matas M., Gavan P. T., York P., Adv. Drug Deliv. Rev., (2007), 59, 617–630. [2] Khankari R. K. and Grant D. J. W., Thermochim. Acta, (1995), 248, , 61–79. [3] Tomkowiak H., Olejniczak A., and Katrusiak A., Cryst. Growth Des., (2013), 13, 121–125. [4] Hao X., Parkin S., and Brock C. P., Acta Crystallogr. Sect. B Struct. Sci., (2005), 61, 689–699. [5] Merrill L., Bassett W. A., Rev. Sci. Instrum. 45, (1974), 290−294. S11-P33
High pressure High temperature (HP / HT) growth of multifunctional
perovskites. How chemical substitutions can be used to switch from a
magnetoresistive to a dielectric (polar) magnet
D. Delmonte*1, F. Mezzadri2, E. Gilioli1, G. Calestani2, M. Solzi3, R. Cabassi1, F. Bolzoni1
1
IMEM-CNR, Parco Area delle Scienze 37/A, 43124 Parma (Italy)
Dipartimento di Chimica, GIAP Università di Parma, Parco Area delle Scienze 17/A 43124 Parma (Italy)
3
Dipartimento di Fisica, Università di Parma, Parco Area delle Scienze 7/A, 43124 Parma (Italy)
2
The study of multifunctional materials is today one of the most relevant branches of the wide
field of Materials Science. Unfortunately such phases are often characterized by complex structural
constraints which usually act as a limiting agent. In particular for what concerns the family of
multiferroics, the coexistence of two or more primary ferroic orders (ferromagnetism,
ferroelectricity and ferroelasticity) requires to respect strict spatial and time inversion symmetry
rules and to produce materials with precise electrical properties (a multiferroic is always an
insulator…). It is not casual that such compounds prevalently crystallize on the basis of the
perovskite structure: due to its large tolerance to structural distortions and chemical substitutions,
perovskites allow to explore wide ranges of physical phenomena.
Specifically, lead-based perovskites, thanks to the very high-T ferromagnetic/ferrimagnetic
character they display often above RT (a very rare phenomenon in known multiferroics), result to
be very promising. However, they are bad candidate for multiferroism since semi-metallic
character, magnetoresistivity and in some cases spin-polarized electrons-mediated transport
(interesting aspects for spintronic applications) is often observed; in few words they are far away to
be good insulators.
In this work we try to explain how we operate to transform a semimetal into a dielectric
(possibly polar) material limiting the weakening of its magnetic response in order to obtain a
multiferroic phase. The strategy goes through a chemical operation on the A site of the perovksite;
Pb ion is partially substituted with an alkali ion (principally K+). The stabilization of such a
different ion in this site can be uniquely provided by means of an enhancement of the isostatic
pressure intensity applied during HP/HT synthesis in our Multianvil press apparatus.
This ECCG5 Congress has been endorsed by the
The ECCG5 would like to thank all exhibitors and sponsors who have generously
contributed to this year’s conference

to it - Imem-Cnr

Transcription

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