ICG2013 - Final Program, List of Abstracts and - Imem-Cnr

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14 – 15 November, 2013 Institute of Materials for Electronics and Magnetism National Research Council
Final Program List of Abstracts List of Poster Presentations Italian Crystal Growth New Frontiers of Functional Materials 14 – 15 November, 2013 IMEM‐CNR Parco Area delle Scienze 37/A ‐ 3124 Parma, Italy http://icg2013.imem.cnr.it Scientific Committee
Conference - Chair
Andrea Zappettini, CNR-IMEM, Parma
Opening session - Chair
Salvatore Iannotta, CNR-IMEM, Parma
Session 1 - Chair
Marco Bruno, Turin University
Session 2 - Chair
Marco Stefancich, Masdar Institute of Science and Technology, Abu
Dhabi, UAE
Session 3 - Chair
Adele Sassella, Milano-Bicocca University
Session 4 - Chair
Tullio Toccoli, CNR-IMEM, Trento
Session 5 - Chair
Nicola Lovergine, Salento University, Lecce
Round table - Chair
Salvatore Iannotta, CNR-IMEM, Parma
Proceedings - Editor
Paola Prete, CNR-IMM, Lecce
Organizing Committee
IMEM Scientific Secretariat
Rosella Magno, Paolo Marmiroli, Antonietta Secondulfo
IMEM Technical Assistance
Vittorio Canevari, Antonio De Sanctis, Luca Martorana, Marco Pola
IMEM Graphical Assistance
Davide Calestani
‐ i ‐ This ICG2013 Congress has been organized and sponsored by the
Italian Crystallographic Association (AIC)
Institute of Materials for Electronics and Magnetism, CNR
Bruker Italia S.r.l.
Gambetti Kenologia Srl
JEOL (ITALIA) S.p.A.
Leica Microsystems Srl
PANalytical S.r.l.
The ICG2013 has also been endorsed by the
International Organization for Crystal Growth
International Union of Crystallography
‐ ii ‐ PROGRAM
Thursday 14, November 2013
8:30-10:00
Registration and Poster display
10:00-10:20
Introduction and Welcome Address
Chair: Andrea Zappettini
Dr. Salvatore Iannotta, Director of the CNR-IMEM
Prof. Roberto Fornari, President of International Organization for Crystal Growth (IOCG)
10:20-11:00
Plenary Lecture
“The power of intermolecular interactions in organic semiconductors: from
threaded molecular wires to PCBM single crystals”
Franco Cacialli, Department of Physics & Astronomy, University College London,
Gower Street, London WC1E 6BT, UK)
11:00-11:20
Coffee break (sponsored by JEOL Italia S.p.A.)
11:20-13:25
Session on “Fundamentals in crystal growth: from bulk to surfaces”
Chair: Marco Bruno
“Prediction of crystal morphology: the faster the better? Some slow-food examples
on organic semiconductors” – invited talk
Massimo Moret
“Anomalous Mixed Crystals: a crystallographic exception or a new emerging rule?”
– invited talk
Linda Pastero
“Influence of Sr on Si crystal growth in Al–Si casting alloys” - talk
Melanie Timpel, Nelia Wanderka, John Banhart
“Crystal growth and spectroscopic characterization of KY3F10: Ho3+” - talk
Daniela Parisi, Stefano Veronesi, Giacomo Bolognesi, Martin Shellhorn and Mauro
Tonelli
“Growth and interface reactions of TiO2 thin crystalline films on Fe(100)” - talk
Alberto Brambilla, A. Calloni, G. Berti, G. Bussetti, L. Duò, and F. Ciccacci
“Use of Multi-Anvil Walker-type Press in growing novel complex materials” - talk
Davide Delmonte, F. Mezzadri, E. Gilioli, G. Calestani, C. Pernechele, M. Solzi, R.
Cabassi, F. Bolzoni
“Growth of high quality layered metal dichalcogenides single crystals” – talk
Alberto Ubaldini, Enrico Giannini
13:25-14:30
Lunch
‐ iii ‐ 14:30-16:25
Session on “Nanoepitaxy”
Chair: Nicola Lovergine
“The role of chemistry in graphene growth and functionalization” – invited talk
Giuseppe Valerio Bianco, Maria Losurdo, Maria Michela Giangregorio, Pio Capezzuto,
Giovanni Bruno
“MOCVD-grown Ge-Sb-Te nanowires for phase change memory” - talk
Massimo Longo, Claudia Wiemer, Roberto Fallica, Toni Stoycheva, Enzo Rotunno,
Laura Lazzarini
“On the MOVPE of AlGaAs shell and its effect on the luminescence of GaAsAlGaAs core-shell nanowires” - talk
Ilio Miccoli, P. Prete, and N. Lovergine
“Sub-critical InAs layers on metamorphic InGaAs for single QD emission at 1.3 1.55 µm” - talk
Luca Seravalli, Giovanna Trevisi, Guillermo Muñoz-Matutano, D. Rivas, Juan MartinezPastor, Paola Frigeri
“Selective growth of InAs Quantum Dots on GaAs driven by As kinetics” - talk
Rita Magri, F. Arciprete, E. Placidi, M. Fanfoni, A. Balzarotti, F. Patella
“Growth Dynamics of GaAs/AlGaAs Quantum dots by Droplet Epitaxy” – talk
Stefano Sanguinetti, S. Bietti, C. Somaschini, A. Fedorov
“Nano-patterned organic heterostructures through organic droplet epitaxy” – talk
Luisa Raimondo, Marcello Campione, Alessandro Borghesi, Adele Sassella
16:25-16:45
Coffee break
16:45-18:50
Session on “Material engineering for PhotoVoltaic conversion in the world of 1 $/W
silicon panels”
Chair: Marco Stefancich
“III-V materials engineering and novel approaches to material deposition for high
efficiency Photovoltaics” - invited talk
Gianluca Timò
“Engineered Photoanodes for High Efficiency Dye - and Quantum Dot - Sensitized
Solar Cells” –invited talk
Isabella Concina, Gurpreet Singh Selopal, Riccardo Milan, Alberto Vomiero, Giorgio
Sberveglieri
“Chalcopyrite based solar materials grown by vacuum and non-vacuum methods” talk
Alessia Le Donne, S. Marchionna, P. Garattini, S. Tombolato, B. Vodopivec, M. Acciarri
and S. Binetti
“A Novel High Load Cvd Reactor For Photovoltaic Applications” - talk
Maurizio Masi, Carlo Cavallotti, Diego Boccalari, Francesco Castellana
“Key Developments in CIGS Thin Film Solar Cells on Ceramic Substrates” - talk
Alessio Bosio, Daniele Menossi, Greta Rosa, Nicola Romeo
‐ iv ‐ “Low temperature fabrication of 15%-efficient solar cells based on Cu(In,Ga)Se2
films by Pulsed Electron Deposition technique” - talk
Matteo Bronzoni, Filippo Annoni, Francesco Bissoli, Marco Calicchio, John Paul Garcia,
Edmondo Gilioli, Francesco Pattini, Stefano Rampino, Vimalkumar Thottapurath,
Massimo Mazzer
20:00
Social dinner
Friday 15, November 2013
8:45-10:55
Session on “Organic and hydrid materials”
Chair: Adele Sassella
“OFETs architectures to sensing biomolecules interactions” – invited talk
Luisa Torsi
“Polymorphism-driven functionalities in thieno(bis)imide organic semiconductors”
– talk
Margherita Durso, Cristian Bettini, Massimo Gazzano, Denis Gentili, Massimiliano
Cavallini, Federico Gallino, Stefano Toffanin, Raffella Capelli, Michele Muccini,
Manuela Melucci
“Stamp assisted crystal growth for new technological applications” – talk
Massimiliano Cavallini, Denis Gentili, Fabiola Liscio, Laura Ferlauto,Margherita Durso,
Manuela Melucci
“Evidence of the stable alignment of porphyrin tautomers, following an
unconventional organic film growth” - talk
Gianlorenzo Bussetti, Marcello Campione, Michele Riva, Andrea Picone, Luisa
Raimondo, Lorenzo Ferraro, Conor Hogan, Maurizia Palummo, Alberto Brambilla,
Marco Finazzia Lamberto Duò, Adele Sassella, Franco Ciccacci
“Self-assembly of Glutamic acid at Ag surfaces: understanding the bio-interface at
the nanoscopic level” – talk
Letizia Savio, M. Smerieri, L. Vattuone, M. Rocca, I. Tranca, D. Costa, F. Tielens
“Single crystalline rubrene: the organic silicon” – talk
Marcello Campione, Silvia Trabattoni, Enrico Fumagalli, Luisa Raimondo, Massimo
Moret, Adele Sassella
“Charge trapping on metal nanoparticles in an organic semiconductor matrix and
light-induced detrapping” – talk
Giovanni Ligorio, Marco Vittorio Nardi, Christos Christodoulou, Martin Brinkmann,
Marc Schmutz, and Norbert Koch
“Bias Stress effects in n-type organic single-crystal and thin-film transistors” – talk
Mario Barra
10:55-11:15
Coffee break (sponsored by PANalytical S.r.l..)
11:15-12:55
Session on “Functional nanostructures”
Chair: Tullio Toccoli
“Functional Magnetic Nanoparticles” – invited talk
‐ v ‐ Alessandro Ponti
“Synthesis and Characterization of Iron Oxide Gold Core/Shell Nanoparticles for
Cancer Care” - talk
Filippo Benetti, Devid Maniglio, Giorgio Speranza, Claudio Migliaresi
“SiO2/SiC core-shell nanowires for nanomedicine applications” - talk
Giancarlo Salviati, F. Fabbri, F. Rossi, L. Nasi, M. Campanini, G. Attolini, D. Sathish
Chander, M. Negri, F. Albertini, F. Casoli, V. Chiesi, R. Verucchi, L. Aversa, M. Nardi,
S. Iannotta, F. Bigi, E. Bedogni, L. Cristofolini, T. Rimoldi, P. Petronini, R. Alfieri, M.
Galetti, A. Mutti, M. Goldoni, R. Alinovi, A. Cacchioli, F. Ravanetti, G. Benecchi, C.
Ghetti
“Nanosizing Crystalline Diamond Array by a Dual-Mode MW-RF Plasma Reactor” talk
Stefano Gay, S. Orlanducci, E. Tamburri, V. Guglielmotti, G. Reina, T. Lavecchia, M. L.
Terranova, M. Rossi
“Hollandite Nanoparticles for Chemical Sensing: Strain or Pseudosymmetry?” - talk
Alice Boschetti and Michele Gregorkiewitz
“Hydroquinone based synthesis of Au nanoparticles with shape control for SERS
applications” - talk
Carlo Morasso, Dora Mehn, Domitilla Schiumarini, Renzo Vanna, Marzia Bedoni, Chiara
Pignatari, Davide Prosperi, Furio Gramatica
12:55-15:00
Poster session with lunch
15:00-17:00
Round table on "Nanomedicine: Demands and Challenges”
Chair: Salvatore Iannotta
Posters will be mounted from THURSDAY to FRIDAY and the
discussion will be on FRIDAY from 12:55 to 15:00.
‐ vi ‐ Poster list:
Session on “Fundamentals in crystal growth: from bulk to surfaces”
“Contact angle and surface energies at the calcite/solution {10.4} interface”
Emanuele Costa, Dino Aquilano
“Effect of Tb3+ co-doping on BaY2F8:Dy3+ crystals”
Daniela Parisi, Giacomo Bolognesi and M. Tonelli
“X-ray diffraction efficiency of bent GaAs (220) mosaic crystals for the LAUE project”
Elisa Bonnini, Elisa Buffagni, Claudio Ferrari, Antonio De Sanctis, Andrea Zappettini
“3D heteroepitaxy on patterned Si substrates: a new monolithic integration strategy”
Stefano Sanguinetti, R. Bergamaschini, S. Bietti, F. Isa, G. Isella, A. Marzegalli, C. Frigeri, F. Montalenti, F.
Pezzoli, A. Scaccabarozzi, C. V. Falub, H. von Känel and L. Miglio
“Impact of heavy doping with donors on CZ silicon properties”
Maria Porrini, Januscia Duchini, Alessia Bazzali
“Epitaxial germanium deposited by MOVPE on InGaAs quantum dot stressors grown by MBE”
Matteo Bosi, Giovanni Attolini, Paola Frigeri, Lucia Nasi, Francesca Rossi, Luca Seravalli, Giovanna Trevisi
“Nanoindentation studies of gallium arsenide grown on germanium”
Joice Sophia Ponraj, Arivuoli Dakshinamoorthy, Giovanni Attolini, Matteo Bosi
“Crystal bending by surface damaging in crystals for a Laue lens”
Elisa Buffagni, Elisa Bonnini, Claudio Ferrari, Andrea Zappettini, Giuseppe M. Guadalupi
“Transient Current Spectroscopy and internal electric field”
Massimiliano Zanichelli, Andrea Santi, Giovanni Piacentini, Maura Pavesi
“Obtaining High quality 3C-SiC thin films on silicon substrate optimizing the SiC buffer layer”
Matteo Bosi, Giovanni Attolini, Marco Negri, Cesare Frigeri, Elisa Buffagni, Claudio Ferrari, Tiziano
Rimoldi, Luigi Cristofolini, Lucrezia Aversa, Roberta Tatti, Roberto Verucchi
“Electroless gold contact deposition on CdZnTe detectors by scanning pipette technique”
Nicola Zambelli, Laura Marchini, Giacomo Benassi, Davide Calestani, M. Pavesi, Andrea Zappettini
Session on “Nanoepitaxy”
“Heteroepitaxy of Ga2-2xIn2xO3 layers by MOVPE with different oxygen sources”
Michele Baldini, Daniela Gogova, Klaus Irmscher, Albert Kwasniewski, Martin Schmidbauer, Günter
Wagner and Roberto Fornari
“Structural and electronic properties of VZn in ZnO nanostructures: a combined experimental and
theoretical study”
Alessandra Catellani, A. Calzolari, F. Fabbri, M. Villani, D. Calestani, A. Zappettini, G. Salviati
“Self assisted growth of GaAs nanowires stopped and resumed”
Silvia Rubini, Giacomo Priante, S. Ambrosini, V.G. Dubrovskii, A. Franciosi
“Epitaxial growth of magnetic thin films and heterostructures for data storage and energy
applications”
Francesca Casoli, Simone Fabbrici, Pierpaolo Lupo, Valentina Chiesi, Paolo Ranzieri, Lucia Nasi, Marco
Campanini, Franca Albertini
“Growth and characterization of germanium nanowires”
Giovanni Attolini, Francesca Rossi, Matteo Bosi
‐ vii ‐ “Uniaxially-oriented epitaxial nanowires of H2TPP”
Marcello Campione, Gian Carlo Capitani, Luisa Raimondo, Massimo Moret, Adele Sassella
“1D transparent conductive oxides for plasmonics: near-infrared activity in In-doped ZnO nanowires”
Arrigo Calzolari, A. Ruini, A. Catellani
“Effect of different catalysts on the vapour phase growth of SiC nanowires”
Paola Lagonegro, S.C. Dhanabalan, M. Negri, G. Attolini, M. Bosi, F. Rossi, M. Campanini, F. Boschi, A.
Bosio, D. Menossb, N. Romeo, G. Rosa, P.P. Lupo, T. Besagni, G. Salviati
“Nanoepitaxial vapor phase growth of vertically aligned ZnO nanowires”
Sathish Chander Dhanabalan, Davide Calestani, Marco Villani, Laura Lazzarini, Francesco Pattinia John
Paul Garcia, Stefano Rampino and Andrea Zappettini
Session on “Material engineering for PhotoVoltaic conversion in the world of 1 $/W silicon panels”
“Target properties and substrate treatment effects on ZnO:Al grown by dc-magnetron sputtering”
Ilio Miccoli, R. Spampinato, P. Prete, and N. Lovergine
“Buried GaSb junctions controlled by native defects in GaAs/GaSb MOVPE structures”
Marco Gorni, Antonella Parisini, Enos Gombia, Michele Baldini, Salvatore Vantaggio, Carlo Ghezzi
“ZnO nano-tetrapods as 3D charge collection and transport channels in SnO2 based”
Pradeep Uththamawadu, Nicola Coppedè, Marco Villani, Davide Calestani, Roberto Mosca, Paolo Fedeli,
Andrea Zappettini
“Material Challenges for high reflectivity in non-imaging concentrator optics”
Marco Stefancich
Session on “Organic and hybrid materials”
“Tuning the work function of graphene with a high molecular weight electron acceptor”
Marco Vittorio Nardi, Christos Christodoulou, Giovanni Ligorio, Martin Oehzelt, Melanie Timpel, Kaled
Parvez, Klaus Müllenc, and Norbert Koch
“Organolead halide perovskites for all-solid-state sensitised solar cells”
Paolo Fedeli, Francesco Gazza, Davide Calestani, Lucia Nasi, Patrizia Ferro, Tullo Besagni, Pavel
Hubik,Gianluca Calestania,Paola Ceroni,Roberto Mosca
“Functionalization of SiC Nanowires by Supersonic Molecular Beams for Photodynamic Therapy”
Roberta Tatti, L. Aversa, R. Verucchi, F. Fabbri, F. Rossi, G. Attolini, M. Bosi, G. Salviati, S. Iannotta
“Crystalline rubrene in epitaxial heterostructures”
Luisa Raimondo, Marcello Campione, Enrico Fumagalli, Massimo Moret, Alessandro Borghesa, Adele
Sassella
“Investigation of the spatial inhomogeneity of the photoluminescence and photovoltaic properties of
inverted all polymer solar cells by confocal spectroscopy”
Andrea Perulli, Sandro Lattante, Anna Persano, Adriano Cola, Massimo Di Giulio and Marco Anni
“The polymorphism of TPB”
Domenico Crocco, Alessia Bacchi, Mauro Carcelli, Alberto Girlando, Matteo Masino
“Epitaxial growth of hexathiophene polymorphs on β-alanine(010) single crystals”
Silvia Trabattoni, Massimo Moret, Marcello Campione, Luisa Raimondo, Adele Sassella
‐ viii ‐ “Epitaxial interfaces in pentacene/perfluoropentacene thin film heterojunctions”
Luisa Raimondo, Marcello Campione, Katharina Broch, Frank Schreiber, Adele Sassella
“Organic electrochemical transistor on cotton fiber as sensor for application in human sweat”
Nicola Coppedè, Giuseppe Tarabella, Marco Villani, Davide Calestani, Roberto Mosca, Salvatore Iannotta,
Andrea Zappettini
“Pentacene thin films growth: optical properties from sub-monolayer up to the bulk”
Mattia Marchio, P. Bettotti, S. Iannotta, T. Toccoli
Session on “Functional nanostructures”
“Antibody functionalized iron oxide nanoparticles loaded to improve drug delivery for tumor car”
Luca Dalbosco, S. Tong, G. Bao, V. Antonini, M. Dalla Serra, R. Morrigl, D. Maniglio, C. Migliaresi
“Zno nanostructures: electrical and optical properties for gas sensing”
Maria Cristina Carotta, Ambra Fioravanti, Sandro Gherardi, Cesare Malagù, Michele Sacerdoti, Stefano
Lettieri, Emanuele Orabona, and Pasquale Maddalena
“Nanostructured Titania: doping, characterization and photocatalytic activity”
Fabio Orlandi, Viola Viganò, Ilaria Alfieri, Andrea Lorenzi, Lara Righi, Angelo Montenero
“Role of In-Situ Grown SiN Passivation for E-Mode AlGaN/GaN MOSHEMTS on silicon substrate for
efficient power converter”
Mattia Capriotti, A. Alexewicz, O. Bethge, D. Visalli, J. Derluyn, C. Fleury, E. Bertagnolli, D. Pogany, G.
Strasser
“Vapour Phase Growth of PbO Nanowires with Extreme Aspect Ratio”
Giacomo Benassi, Davide Calestani, Nicola Zambelli, Andrea Zappettini
“Local current mapping on polycrystalline sexithiophene thin films by conductive atomic force
microscopy”
Sreejith Embekkat, Adele Sassella, Olivier Douhéret, Roberto Lazzaroni and Alessandro Borghesi
“Synthesis of lithium intercalated fullerene and fullerane for applications in Li-ion batteries”
Giovanni Riva, Daniele Pontiroli, Matteo Aramini, Mattia Gaboardi, Alessio Gaimarri, Samuele Sanna,
Chiara Milanesc and Mauro Riccò
“Synthesis of nickel decorated graphene and study of its interaction with hydrogen”
Giacomo Magnani, Mattia Gaboardi, Giovanni Bertoni, Andreas Bliersbach, Daniele Pontiroli, Matteo
Aramini, Georgia Vlachopoulou, Mauro Riccò, Giancarlo Salviati
“Sythesis and structural characterization of Li12C60”
Fabio Giglio, Daniele Pontiroli, Mattia Gaboardi, Matteo Aramini, Chiara Cavallari, Michela Brunelli,
Mauro Riccò
“Synthesis and characterization of the Mg2C60 ionic conductor”
Silvia Virdis, Daniele Pontiroli, Matteo Aramini, Mattia Gaboardi, Fabio Orlandi, Lara Righi, Gianluca
Calestani and nd Mauro Riccò
“Silylation route toward novel multifunctional (nano)composites”
Margherita Durso, Tamara Posati, Anna Sagnella, Valentina Benfenati, Giampiero Ruani, Vincenzo Palermo,
Roberto Zamboni, Manuela Melucci
“Hierarchical assembly of CuO nanostructures for photocatalytic application”
Marco Villani, Aderemi Babatunde Alabi, Nicola Coppedè, Laura Lazzarini, Davide Calestani and Andrea
Zappettini
“Ethanol gas sensing mechanism for ZnO nanowires”
‐ ix ‐ Kiptiemoi K. Korir, G. Cicero and A. Catellani
“Piezoelectric properties of zinc oxide nanowires: An ab-initio study”
Kiptiemoi K. Korir, A. Catellani, and G. Cicero
“Functionalization of SiC/SiO2 NWs with MNPs or porphyrins via ‘click’ chemistry”
Elena Bedogni, A. Secchi, M. Campanini, L. Nasi, F. Rossi, V. Chiesi, F. Casoli, F. Albertini, T. Rimoldi, L.
Cristofolini, G. Attolini, M. Negri, G. Salviati and F. Bigi
“Study of nanostructures based on SiC/SiO2 for the realization of a prototypal microdevice as
subretinal implant: Cytotoxicity tests”
Paola Lagonegro, F. Rossi, G. Attolini, M. Bosi , F. Boschi, M. Negri, T. Rimoldi, L. Cristofolini, R.
Alinovi, S. Pinelli, A. Mutti, C. Macaluso and G. Salviati
“ZnO nanotetrapods as advanced tools for nanomedicine and water remediation”
Marco Villani, Davide Calestani, Nicola Coppedè, Laura Lazzarini, Francesca Casoli, Valentina Chiesi,
Franca Albertini, Tiziano Rimoldi, Nicola Castagnetti, and Andrea Zappettini
“Properties of ZnO nanorods grown by hydrothermal synthesis on conductive layers”
L.V. Podrezova, V. Caudab, S. Stassi, Giancarlo Cicero, Kh.A. Abdullin, B.E. Alpysbaeva
“Deposition via spray deposition of Cu2S efficient counter electrodes for quantum dot sensitized solar
cells”
Isabella Concina
“Scale-up of an electrochemical anodization process for the production of nanostructured WO3
photoanodes”
Giuseppe M. Guadalupi, Marcello Marella, Marco Guidolin, Fabio Gerolin, Marino Battagliarin, Laura
Meda, Alessandra Tacca, Fabio Oldani
‐ x ‐ Plenary lecture The power of intermolecular interactions in organic semiconductors: from threaded molecular wires
to PCBM single crystals
Giulia Tregnago,a,b Giuseppe Maria Paternò,a,b Nico Seidlera,b and Franco Caciallia,b
Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, United Kingdom
London Centre for Nanotechnology, Gower Street, London WC1E 6BT, United Kingdom
E-mail: [email protected]
a
Over the last 40 years the versatility of organic chemistry has allowed significant progress in achieving control over the solid-state
properties of functional organic molecules, the attention being focused especially on covalent bonding and on tailoring of
“intramolecular functionality”. Control at the intermolecular level is more elusive, but still crucial for manipulating and optimising
relevant properties of the functional materials, such charge transport or luminescence.
Threaded molecular wires made with conjugated-polymers-based polyrotaxanes offer an example of a “bottom-up” approach to
electroluminescent nanostructures incorporating supramolecular design concepts.[1] Namely, this class of materials is engineered at a
supramolecular level by threading a conjugated macromolecule, such as poly(para-phenylene), poly(4,4’-diphenylene vinylene) or
poly(9,9’-fluorene) through - or -cyclodextrin rings, so as to reduce solid-state packing effects that red-shift and partially quench
the luminescence. Such a supramolecular approach preserves the fundamental semiconducting properties of the conjugated wires,
and is effective at both increasing the photoluminescence efficiency and blue-shifting the emission of the conjugated cores, in the
solid state, while still allowing charge-transport and thus electroluminescence (EL). The reduced tendency for polymer chains to
aggregate shows in both solid-state films and in solution (as probed by fluorescence decay dynamics) and allows solution-processing
of individual polyrotaxane wires onto substrates, as revealed by scanning-force microscopy.[2] Control of the threading ratio is
possible, thereby resulting in fine tuning of the excitonic vs. aggregate contribution to the luminescence, as well as of the electro- and
photo-luminescence efficiency.[3] An intriguing possibility afforded by supramolecular and nanoscale encapsulation of these soluble
semiconductors is the suppression of energy transfer which enables both fabrication of white-emitting LEDs,[4] and achievement of
unprecedentedly broad gain bands, in “conjugated” blends of different semiconductors, with potential application to broad-band
amplifiers and multi-colour lasers.[5] Water solubility of rotaxanes carrying un-substituted cyclodextrins also enables their
incorporation into stretchable matrices and thus strong polarisation of absorption and emission from such films.[6]
Whereas design of materials for luminescent application is generally aimed at partial or total suppression of intermolecular
interactions, and in particular of pi-pi stacking, applications relying primarily on charge transport such as field-effect transistors
(FETs) and photovoltaic diodes (PVDs) require optimisation of charge mobility, which is favoured, in turn, by strong intermolecular
interactions and tight packing, as common in crystalline structures. In the second part of the talk I will present recent results on
poly(3-hexylthiophene-2,5-diyl) (P3HT)-based nanofibres whose optical and transport properties are also strongly influenced by
intermolecular interactions through enhanced cristallinity (compared to non-nanostructured films).[7] Finally, I will conclude by
reporting the recent preparation and characterisation of solvent-free, high-quality and large (100s of micrometers) single crystals of
[6,6]-phenyl-C61-butyric acid methyl ester (PCBM).[8]
[1] F. Cacialli, J.S. Wilson, et al., Nature Materials. 2002, 1, 160. [2] J.S. Wilson, M.J. Frampton, et al, Adv. Mat. 2005, 17, 2659. [3] S. Brovelli, G.
Latini, et al., Nano Letters 2008, 8, 4546. [4] S. Brovelli, F. Meinardi, et al., Adv. Funct. Mat. 2010, 20, 272. [5] S. Brovelli, T. Virgili, et al., Adv.
Mat. 2010, 22, 3690. [6] F. Di Stasio, P. Korniychuk, et al., Adv. Mat. 2011, 23, 1855. [7]. G.M. Paterno’, A. Warren, et al., J. Mater. Chem. C. 2013,
1, 5619. [8] N. Seidler, G.M. Lazzerini, et al. J. Mater. Chem. C. In press, 1, xxxx . (DOI:10.1039/c3tc31284d)
1 Fundamentals in crystals grwoth: from bulk to surfaces Prediction of crystal morphology: the faster the better? Some slow-food examples on organic semiconductors
Massimo Moret
Department of Materials Science, University of Milano-Bicocca, Milano, Italy
Prediction of properties is, in general, extremely relevant for scientific and technological goals. In the field of crystal growth,
morphology is a fundamental and delicate issue to be dealt with. Our capability to understand, and hopefully to control, the
morphology of crystals has been improved over the years thanks to new models and theories, increased computational power, and the
development of more general and reliable force fields. Within this frame, there is however the tendency to reduce as much as
possible the time spent for performing the calculations required to estimate the relative growth rate of crystal faces, in order to predict
the morphology of crystals. Following this approach, we can have on our desktop in a few seconds the theoretical morphology of our
crystals, being expert or not in this field. By doing this, we are prone to forget crystal growth mechanisms and possible pitfalls
present in physical models, going straight to write a paper or to setup an industrial process. The classical, but more time-consuming,
approach based on the Periodic Bond Chains (PBC) theory introduced by P. Hartman and W.G. Perdok, has been applied to several
case studies concerning organic semiconducting crystalline phases. Application of the PBC theory successfully allows to extract the
main features of growth morphologies for oligothiophenes and oligoacenes. Moreover, the deep structural study involved in the PBC
analysis provides unique information about surface morphological features, including the shape of two-dimensional nuclei. Thus, the
richness of data provided by this more demanding approach rewards more than simpler and faster black-box strategies. [1] P. Hartman, W.G. Perdok Acta Crystallogr. 1955, 8, 49 ; [2] ibid. 521 ; [3] ibid. 525 ; [4] P. Hartman, P. Bennema J. Crystal Growth 1980, 49,
145.
Anomalous Mixed Crystals: a crystallographic exception or a new emerging rule?
Linda Pasteroa, Dino Aquilanoa
a
Dipartimento di Scienze della Terra, Università degli Studi di Torino, Torino, Italy
Anomalous mixed crystals (AMX), in the Johnsen and Neuhaus sense [1], [2], originate from an ordered distribution of crystallites
(guest phase) into a bulky crystal (host phase). Then, they differ from the traditional mixed crystals that are originated by zoning or
sector growth. Optical microscopy (through pleochroism and anomalous birefringence) is the ready technique to reveal this peculiar
anomaly, but several other techniques could be useful and their results can give rise to a quantitative interpretation, for example
XRPD, luminescence, elemental analysis (EDS).
The basic requirements for AMX formation are: i) good parametric and angular coincidence between host and guest crystal planes
(2D epitaxy); ii) a weak dhkl misfit between the thickness of the elementary layers, of both host and guest phases, which share the 2D
coincidence lattice plane.
Ever since the earliest works, it was accepted that many systems could give rise to AMX. Actually, the AMX formation seems to be
more a rule than an exception in many crystal-chemical systems and shares the same concepts as the thin film growth, so widely used
in industrial applications.
The following examples are a not exhaustive review of the variety of systems leading to the formation of the AMX we experienced.
1) Ad-sorption and 2D epitaxial growth originated by good coincidences between in-plane crystallographic parameters of host and
guest phases: a) The Halite/Halite system as example of auto-epitaxy; b) The Halite/Alizarine system [3]; c) The YBCO/Cu-oxides
system ; d) The Quartz/Witherite (BaCO3) system [4]
2) Ab-sorption and AMX formation, as thin guest lamellae into the host crystal (3D parametric coincidences between guest and host
crystals). In this case the guest phase can grow at unsaturation values: a’) CaCO3/Li2CO3 system (calcite K and S faces become stable
and morphology changes set up) [5]; b’) Alkali-halides/Formamide system (AMX with an organic component inducing a K-face
stabilization) [6]; c’) Calcite/Apatite system
3) AB-sorption as continuity behaviour between “morphodrome” and phase diagram (smooth transition between the first and the
second as a function of the host/guest concentration ratio): a’’) CaCO3/Li2CO3 system [5]; b’’) KCl / PbCl2 system [7]
[1] A. Johnsen, Wachstumund Auflösung der Kristalle, Engelmann, Leipzig, 1910 ; [2] A. Neuhaus, Z.Krist. 1928 68 15 ; [3] R. Kern, Cryst. Res.
Technol., 2013 1 ; [4] E. Bittarello et al., Journal of Crystal Growth, 2010 312/3 402 ; [5] L. Pastero et al., Crystal Growth and Design 2004 4/3 485 ;
[6] L. Pastero et al., Crystal Growth and Design 2012 12 2306 ; [7] L. Lian et al. Journal of Crystal Growth 1990 99 150.
2 Melanie Timpel a, Nelia Wanderkab, John Banhartb,c
a
Humboldt University Berlin, Berlin, GermanybHelmholtz Centre Berlin, Berlin, Germany
b
Technical University Berlin, Berlin, Germany
Treatment of Al–Si alloys through the addition of microstructure-modifying elements such as Na or Sr is applied industrially in order
to improve the mechanical properties of these materials [1]. Additions of Sr as small as 120 ppm change the morphology of the
eutectic Si crystal in Al–Si casting alloys from a coarse plate-like to a fine fibrous network, which is known as chemical modification
of the eutectic microstructure. In order to understand this industrially important but hitherto insufficiently understood modification
effect, Al–10wt.Si (200 ppm Sr) cast alloys were investigated in atomic resolution by atom probe tomography and in nanometre
resolution by transmission electron microscopy [2].
Fig. 1 Atom probe tomography of eutectic Si phase in Al–10 wt.% Si alloy modified by 200 ppm Sr. (a) and (b) 3-D reconstruction of Sr atoms
showing the iso-concentration surface representing 0.6 at.% Sr that is used to define the Si/Sr–Al co-segregation interface. (c) Proxigram showing Sr,
Al and Si concentrations as a function of distance to the Si/Sr–Al co-segregation interface given in (a) and (b), respectively.
The combined investigations indicate that Sr co-segregates with Al within the eutectic Si crystal and forms an intermetallic
compound whose chemical composition is close to SrAl4Si20. Two types of segregations are found: One type with linear 3D
morphology is located at the twins of the eutectic Si crystal (Fig. 1). SrAlSi compounds at such positions are responsible for the
formation of multiple twins and their increase in number density during crystal growth. Another type comes as more extended planar
3D morphology and controls the branching of the eutectic Si crystal during growth. The results can be related to previously
postulated growth theories of modification [3, 4] based on adsorption of the chemical modifier elements onto active {111} Si growth
sites. The theories described in the literature will be discussed according to the results obtained in the present work.
[1] Sigworth G.K., Journal of Metalcasting 2008, 2, 19 ; [2] Timpel M., Wanderka N., et al., Acta Materialia 2012, 60, 3920 ; [3] Day M.G.,
Hellawell A., Proceedings of the Royal Society A 1968, 305, 473 ; [4] Lu S.Z., Hellawell A., Metallurgical and Mate
Crystal growth and spectroscopic characterization of KY3F10: Ho3+
Daniela Parisia, Stefano Veronesia, Giacomo Bolognesib, Martin Shellhornc and Mauro Tonellia,d
a
Istituto Nanoscienze NEST - CNR, Pisa, Italy
b
INRIM Istituto Nazionale di Ricerca Metrologica, Torino, Italy
c
French-German Research Institute, ISL, Saint-Louis, France
d
Dipartimento di Fisica, Pisa, Italy
3 Fundamentals in crystals grwoth: from bulk to surfaces Influence of Sr on Si crystal growth in Al–Si casting alloys
Fundamentals in crystals grwoth: from bulk to surfaces E-mail: [email protected]
Laser sources emitting in the 2 µm region are very attractive for a number of possible applications such as medical surgery, optical
communications, security, detection of pollutants, coherent laser radar and frequency combs. Although a KY3F10 (KYF) crystal was
grown for the first time in 1971, its potential as a laser medium in the eye-safe 2 μm spectral region was investigated only for a
crystal doped with Tm3+ [1]. Holmium lasers are, however, preferred over thulium ones due to their longer operating laser
wavelength, benefiting from higher atmospheric transmission and lower absorption in nonlinear crystals for Mid-IR light generation.
In this work we report on growth and spectroscopic characterization of a sample of KY3F10: 0.8at% Ho3+. The crystal melting point is
about 1330 K, has a cubic lattice (space group Fm3m) with cell parameter a=11.553 Å, and the unit cell contains eight formula units
[2]. Due to its isotropy this host is appealing to be utilized in ceramic form for commercial devices. It possesses also good optical and
thermo-mechanical properties. The KYF10: Ho3+ was grown in the Pisa Physics Department Laboratories - National Enterprise for
nano Science and Technology laboratories, that are equipped with a home-made Czochralski furnace with conventional resistive
heating, from oriented seeds. The KYF material is not so easy to grow because of the presence of micro-defects that can appear in the
growth run; but we patented with a new method that improve the Czochralskii crystal growth technique and enable us to obtain
samples very clear and without any defects inside the boule [3]. The choice of this fluoride material means a special care to the
quality of the vacuum system inside the growth chamber (pressure limit below 10-7mbar) in order to avoid the OH- contamination
inside the crystal, that can affect irreparably the laser performance of the samples. The shape of the crystal was monitored with an
computer-controlled optical apparatus, utilizing a CCD camera and a diode laser. In fig. 1 is shown the boule as grown; it is possibile
to see the transparency of the sample sign of the good quality inside the crystal.
We measured at the first step the room temperature absorption spectra by a CARY 500 spectrophotometer in the 2 μm region,
corresponding to 5I8 → 5I7 transition and also in a large wavelenght region (350 – 1500 nm) in order to verify the typical absorption
transitions of Ho3+ ion.
Fluorescence measurements have been performed with a standard apparatus exciting the sample with a NICHIA blue diode laser
tuned at 445 nm, according to the absorption spectrum of Ho:KYF. Our attention was focused on the transition 5I7 → 5I8 (18002200nm) using an InSb detector. The resolution of the spectra was 1.5 nm. As an example we report in Fig 2 the fluorescence
spectra.
Fig. 1. Boule of KY3F10: 0.8% Ho3+ as grown
Fig. 2. Room temperature fluorescence spectra of KY3F10: 0.8%
Ho3+ in the 2µm region
The lifetime at low excitation were measured pumping
the sample with a pulsed tunable Ti:Al2O3 (pulse duration
30 ns) laser tuned around 890 nm and was measured to be τ=14.4±0.5 ms which is comparable to the lifetime of holmium in other
fluoride hosts.
The sample under investigation showed room-temperature continuous-wave laser operation on the 5I7 → 5I8 transition using a Tmdoped silica fiber laser operating at 1938 nm as a pump source. The maximum laser power of 1.8 W was obtained at a wavelength
of~ 2040 nm for 27 W of absorbed pump power with a slope efficiency of 19.1 % with respect to absorbed power. [4]
[1] A. Braud, P. Y. Tigreat, J. L. Doualan, R. Moncorge, Appl. Phys. B 2001, 72, 909 ; [2] A. Grzechnik, J. Nuss, K. Friese, J.-Y. Gesland, and M.
Jansen, Z. Kristallogr. 2002, 217, 460 ; [3] Daniela Parisi, Stefano Veronesi, Mauro Tonelli, “Crescita di monocristalli di KY3F10 drogati con ioni
trivalenti di terre rare” number TO2011A000335 ; [4] M. Schellhorn, D. Parisi, S. Veronesi, G. Bolognesi, M. Eichhorn, and M. Tonelli, Opt. Lett.,
2013, 38, 504
Growth and interface reactions of TiO2 thin crystalline films on Fe(100)
Alberto Brambilla, A. Calloni, G. Berti, G. Bussetti, L. Duò, and F. Ciccacci
CNISM and Dipartimento di Fisica, Politecnico di Milano Piazza Leonardo Da Vinci 32, 20133 Milano, Italy
Titanium dioxide (TiO2) has been the subject of intense studies in recent years, due to its photoelectric and photochemical properties
and its high refractive index and dielectric constant. Thanks to such properties, many applications have highlighted the crucial role
4 [1] U. Diebold, Surf. Sci. Rep. 2003, 48, 53 ; [2] Finetti et al., Surf. Sci. 2008, 602, 1101 ; [3] Papageorgiou et al., J.Phys. Chem. C 2007, 111,
7704 ; [4] A. Brambilla et al., J. Phys. Chem. C 2013, 117, 9229 ; [5] Calloni et al., Thin Solid Films 2012, 520, 3922.
Use of Multi-Anvil Walker-type Press in growing novel complex materials
Davide Delmontea, F. Mezzadrib, E. Giliolib, G. Calestanib-c, C. Pernechelea, M. Solzia, R. Cabassib, F. Bolzonib
a
Dipartimento di Fisica, Università di Parma, Parco Area delle Scienze 7/A, 43124 Parma, Italy
b
IMEM-CNR, Parco Area delle Scienze 37/A, 43124 Parma, Italy
c
Dipartimento di Chimica, GIAP Università di Parma, Parco Area delle Scienze 17/A 43124 Parma, Italy
The study of complex functional materials is today one of the most relevant branches of the basic research in Materials Science.
Unfortunately such phases are often characterized by complex structural constraints that often act as a limiting agent. For instance in
the family of multiferroics, where the coexistence of two or more primary ferroic orders requires precise spatial and time inversion
symmetry rules; on the other hand in High TC superconductors, the complex crystallographic arrangement is directly responsible for
the Cooper-pairs transport mechanism. It is not casual that these two big classes of compounds are based on the perovskite structure:
due to its large tolerance to structural distortions and chemical substitutions, perovskites allow to explore wide ranges of physical
phenomena. In the synthesis of new perovskite-based compounds high pressure is a powerful tool because it permits to stabilize
metastable phases, high density structures with unusual coordination numbers and high oxidation states. The Multi-Anvil Press
Walker-type allow to perform solid state reactions under the application of high isotropic pressures (from 3 GPa up to 20 GPa) and at
high temperatures (from 0 up to 2200°C). We present our laboratory potentiality in the production of complex perovskites; examples
of the significant results in terms of the physical behaviour are capitalized to show also the set of proper characterization techniques
developed.
Growth of high quality layered metal dichalcogenides single crystals
Alberto Ubaldini, Enrico Giannini
DPMC University of Geneva, Geneva, Switzerland
Layered transition metal chalcogenides, MX2 (X = S, Se or Te) have been studied for a very long time because this family includes a
variety of compounds with a wide spectrum of electronic properties (semiconducting, semimetals, superconductivity and charge
ordering). For example, tunability of the electronic structure in TiSe2 by copper intercalation has motivated investigations on the
interplay between superconductivity and charge ordering.
More recently these materials have attracted a growing interest as being promising candidates for novel electronics, complementary
to graphene. Recent studies on exfoliated semiconducting MoS2 mono-layers have shown that effective, atomically thin transistors
can be prepared. Despite of long standing reports on the crystal growth of MX 2 and wide growing interest in this materials, many
details of the growth process (in most of the case, the crystals are prepared by Chemical Vapour Transport, CVT) and optimum
experimental conditions still remain overlooked. In this work, we report the results of a systematic investigation of the effects of
various parameters, like temperature, thermal gradient, nominal composition, total pressure, concentration of the transport agent and
5 Fundamentals in crystals grwoth: from bulk to surfaces played by the TiO2 surface (see Ref. [1] for a comprehensive review). Many of the fundamental properties that are at the basis of the
applications are related to surface and interface properties of TiO2 coupled to other materials, in particular metals. Such studies
would substantially benefit from the use of thin oxide films. For instance, the possibility of synthesizing new titanium oxide phases at
low coverages has been demonstrated [2,3]. Additionally, the oxide surface can be electrically and magnetically coupled with the
substrate, possibly inducing interesting new phenomena.
We report on the growth of thin TiO2 layers on pre-oxidized Fe(100) substrates by Ti deposition in a reactive O2 atmosphere [4]. The
experimental approach followed for the growth on Fe(001) is based on our results recently obtained for the growth of thin rutile TiO2
films on Au(100), that will be also presented and discussed [5]. In particular, we have shown in such a case that a crystalline and
stoichiometric TiO2(100) oxide could be produced by Ti reactive deposition with the substrate held at 300 °C, while the growth at
room temperature (RT) produced a defective oxide. In particular, we will report on experimental results based on X-ray
photoemission spectroscopy (XPS), ultraviolet photoemission spectroscopy (UPS), inverse photoemission spectroscopy (IPES) and
low energy electron diffraction (LEED). We observed that growing TiO2 on Fe(100) at 300 °C produced stoichiometric films but was
characterized by a significant chemical mixing at the interface, with part of the oxidized Fe layer segregated to the sample surface.
On the other hand, the room temperature growth allowed us to greatly reduce the effects of the interface reactions and to avoid the
surface segregation, while the TiO2 layer was featuring the presence of oxygen vacancies. Finally, we have also investigated the
possibility of using a gold buffer layer to obtain better quality TiO2 films on Fe(001), resulting in crystalline rutile films with a
reduced number of oxygen vacancies when compared to room temperature grown samples.
Fundamentals in crystals grwoth: from bulk to surfaces its nature, and annealing time on the crystal growth of semi-metallic TiSe 2, superconducting CuxTiSe2, TaX2 and the
semiconducting MoX2 (X = S, Se, Te) and WSe2. By optimizing the temperature, the temperature gradient and the initial
concentration of chemical transport agent, very large crystals of about 1 cm2 were grown within one day, instead of several days as
usually reported. In particular, the effect of the I2-M ratio has been better clarified, highlighting that the transport and growth
mechanism occur via the formation of highly volatile iodides, like TiI4, that determines the nucleation rate. The growth kinetic is
very fast at the beginning of the process and, depending on the temperature, mm2 sized crystals can grow in few hours. Copper
intercalated crystals could be grown either directly from a mixture of Cu, Ti, Se, using iodine, or by intercalating Cu atoms in already
grown TiSe 2 crystals. In both cases, the copper content can be controlled and superconducting crystals are obtained. The
effects of the nominal starting composition, in additions to the others factors, is discussed Interestingly, iodine is proven not to be
the most effective transport agent for the heavy transition metals, like Mo and Ta. For this reason, a new growth route, starting from
mixtures of chlorides, MoCl 5, TaCl5 or WCl6 and their metals, was successfully gone through. In this case, the upper temperature
was found to be the most critical parameter must be tuned as a function of the chalcogen element. This allows also the selective
growth of only one of the possible politypes of the these materials. The morphology of the crystals depends on the starting chlorine
concentration and whiskers of TaSe 2 as thin as few µm and several mm long were found to grow when the Cl/Ta is too high.
6 The role of chemistry in graphene growth and functionalization
Giuseppe Valerio Bianco, Maria Losurdo, Maria Michela Giangregorio, Pio Capezzuto, Giovanni Bruno
Institute of Inorganic Methodologies and of Plasmas, IMIP-CNR, Department of Chemistry, University of Bari, via
Orabona 4, 70126 Bari, Italy
7 Nanoepitaxy Graphene is defined as a single atomic layer of sp2 bonded carbons in a honeycomb lattice. This emerging material posses peculiar
properties such as high carrier mobility, optical transparency, flexibility and high chemical resistance that have stimulated a vast
amount of research in several scientific fields. The widespread investigation of graphene properties begins since the first isolation of
a graphene flakes by the well-known mechanical exfoliation method (demonstrated in 2004 by Novoselov et al). Whereas mechanical
exfoliation of graphene allows the production of high quality graphene on the laboratory scale for characterization and fundamental
studies, the graphene technology mainly relies on two other fabrication techniques: (i) the growth of epitaxial graphene (E-graphene)
on SiC for substituting silicon in high value-added electronic devices (with operating speeds up to the terahertz range), and (ii) the
growth of graphene on large area metal substrates by chemical vapor deposition (CVD) for applications as flexible conducting
transparent electrodes for replacing ITO technology and developing new flexible electronics.
Currently, the production of CVD- and E-graphene is characterized by a very high cost and a poor control of the graphene
polycrystalline nature (grain sizes and orientations) and thickness (the growth of an uniform single- or bi-layer graphene is still
challenging). These factors as well as the presence of structural defects and impurities (also deriving from the transfer process in the
case of CVD-G) strongly affect the graphene transport properties. Additionally, the opening of an optical gap is fundamental for
graphene applications in transistors, circuits and photonic devices.
This contribution discusses the role of chemistry in addressing the graphene research challenges. Chemical routes for optimizing the
growth of E-graphene and CVD-graphen in terms of quality (grain size, number of layer, presence of defects, etc.) and
reproducibility are presented. These routes are based on the control of the graphene growth kinetics. Moreover, results on the
covalent and non-covalent chemical functionalization of graphene for band-gap engineering, doping, creation of magnetism, and for
anchoring organic molecules and metal nanoparticles.
MOCVD-grown Ge-Sb-Te nanowires for phase change memory
Massimo Longoa, Claudia Wiemera , Roberto Fallicaa, Toni Stoychevaa, Enzo Rotunnob, Laura Lazzarinib
Laboratorio MDM, IMM-CNR, Agrate Brianza, Italy
b
IMEM-CNR, Parma, Italy
Nanoepitaxy a
Phase Change Memories (PCM) are promising data storage devices based on the reversible phase switch induced in the active
material by ns current pulses; information can be stored by relating the binary codes to the significantly different resistivity values of
the material crystalline and amorphous states. An effective way to increase the PCM performance and reduce power consumption is
to scale down the devices by realizing self-assembled nanowire (NW)-based PCM, obtained through vapor-liquid-solid mechanism in
a MOCVD reactor. The largely employed materials forming the NWs are based on chalcogenide alloys belonging to the
pseudobinary tie line of the Ge-Sb-Te system, in particular GeTe, Ge1Sb2Te4, Ge2Sb2Te5, Ge-doped Sb-Te and Sb2Te3 [1-4]. In this
work, large area (SEM, XRD, TXRF) and local area analysis (HRTEM, STEM, EDX) were coupled to the electrical analysis to
provide a panorama of the growth mode, structure and phase change properties of the grown Ge-Sb-Te NWs. In particular, it was
possible to identify an unexpected structure for Ge-doped SbTe NWs.
Fig. 1: HRTEM image of a Ge3Sb29Te68 nanowire, exhibiting twinning superlattice.
Indeed, when a small amount of Ge, below 3%, was introduced, the morphology and the crystal structure of the Sb2Te3
NWs completely changed. All the analysed NWs showed a very regular array of defects (twins), equally spaced along
the whole wire, as shown in the HRTEM image reported in figure 1.We also found the crystal structure to be different
from any other proposed in the literature. Instead of the thermodynamic stable R -3m: H phase of Sb2Te3, with lattice
parameters a = 0.423 nm and c = 3.046 nm, HRTEM revealed compatibility with the P -3 m1 structure. The new
structure was refined by means of HRTEM imaging, electron and X-ray diffraction and STEM-HAADF imaging. The c
lattice parameter was determined by XRD by considering the angular position of the 00l diffracted maxima. The
obtained value was used to simulate HRTEM images. The refined structure was featured by a simple hexagonal unit cell
(S.G. P-3m), having lattice parameters a = 0.426 nm and c = 1.060 nm. NWs of pure Sb2Te3 and Ge-doped SbTe were
employed to fabricate nanowire field-effect transistors with a back-gate terminal by a combination of e-beam
lithography and focused ion beam. The in-plane (c-axis direction) electrical mobility in Sb2Te3 nanowires was 4.25
cm2/Vs, while the out-of-plane mobility in Ge-doped Sb2Te3 nanowires was markedly lower, 0.68 cm2/Vs. This findings
are consistent with previous evidence of anisotropy in hexagonally layered chalcogenides.
[1] M. Longo, C. Wiemer et al., J. Cryst Growth, 2011, 315, 152 ; [2] M. Longo, T. Stoycheva et al., J. Crystal Growth, 2013, 370, 323 ; [3] E.
Rotunno, L. Lazzarini et al., NanoScale, 2013, 5, 1557 ; [4] M. Longo, R. Fallica et al., Nano Lett., 2012, 12, 1509.
On the MOVPE of AlGaAs shell and its effect on the luminescence of GaAs-AlGaAs core-shell nanowires
Ilio Miccolia, P. Preteb, and N. Loverginea
a
Dip. di Ingegneria dell’Innovazione, Univ. del Salento, Lecce, Italy
b
IMM-CNR, Lecce, Italy
Nanowires (NWs) based on III-V compound semiconductors have gathered considerable interest in recent years and are expected to
impact several technological fields, ranging from nanoelectronics [1] to nanophotonics [2, 3], by offering both improved materials
properties and novel device geometries.
8 Present results constitute a significant advancement towards a better understanding and control of the bottom-up fabrication and
properties control of III-V based core-shell NW arrays.
[1] Tomioka K., Yoshimura M., et al.; Nature 2012, 488, 189-192 ; [2] Wallentin J., Anttu N et al., Science 2013, 339, 1057-1060 ; [3] Krogstrup,
P.; Jørgensen, et al., Nature Photonics 2013, 7, 306–310 ; [4] S. Wagner, and W.C. Ellis, Appl. Phys. Lett. 1964, 4, 89 ; [5] I. Miccoli, P. Prete, and
N. Lovergine, submitted (2013) ; [6] P. Prete, I. Miccoli, et. al, Phys. Status Solidi RRL, ın press (2013) [DOI 10.1002/pssr.201308046] ; [7] Hocevar
M., Giang L.T.T, et.al., Appl. Phys. Lett. 2013, 102, 191103.
Sub-critical InAs layers on metamorphic InGaAs for single QD emission at 1.3 - 1.55 µm
Luca Seravallia, Giovanna Trevisia, Guillermo Muñoz-Matutanoc, D. Rivasb, Juan Martinez-Pastorb , Paola Frigeria
a
IMEM-CNR, Parco Area delle Scienze, 37/a, I-43100 Parma, Italy
b
Instituto de Ciencia de los Materiales, Universitat de València, P.O. Box 22085, 46071 Valencia, Spain
c
Optics and Quantum Comunications group, ITEAM, UPV, Valencia, Spain.
Single self-assembled semiconductor quantum dots (QDs) are one of the promising candidates to build versatile photon sources in
quantum information science and one of the most important quest for present research is today the engineering of the structure to
match the QD emission with wavelengths of standard telecommunication technology (1.3 - 1.55 µm). [1]
Here we report on the design, the growth by MBE and the optical and morphological characterization of metamorphic InAs/InxGa1xAs QDs with a density low enough to allow single dot characterization without the need of complex litographic steps to isolate
single QDs. [2]
9 Nanoepitaxy Due to the high (~106 cm/s) surface carrier recombination velocity of GaAs and the nanowire large surface-to-volume ratios,
effective and long-term stable passivation of GaAs surface states is however, necessary. A common approach is to overgrow a wider
bandgap AlGaAs shell around GaAs nanowires. GaAs-AlGaAs core-shell nanowires thus show strong enhancement of luminescence
intensity, improved minority carrier diffusion lenghts, and recombination lifetimes with respect to bare GaAs nanowires.
Despite the growth of GaAs-AlGaAs core-shell NWs by MOVPE has been already demonstrated, no systematic studies on the effects
of different epitaxial growth conditions on such nanostructures have been reported so far. Moreover, while many efforts have been
devoted until today to modeling the growth of NWs through the Vapor-Liquid-Solid mechanism [4], a full understanding and control
of the AlGaAs shell growth dynamics, materials composition, and its effects on NW radiative and structural properties, is still largely
lacking especially in the case of dense ensembles.
In the present work, it is demonstrated for the first time that, for a fixed set of MOVPE parameters, the NW core diameter, height and
array density couples together to determine the shell growth rate. In particular, the shell thickness is observed to decrease by
increasing the NW array density between 107 and 109 cm-2. A mass-transport limited growth model is proposed and validated to
explain the observed dependencies in good agreement with experimental data; the model predicts a conformal growth of the shell
material over the whole sample surface [5]. The results herewith exposed are extremely important from the viewpoint of the shell
growth processes, as well as for the controlled fabrication of core-shell and core-multishell NWs of interest for future device
applications.
The photoluminescence (PL) core emission of present GaAs-AlGaAs core-shell NWs was further studied as function of the NW
relevant geometrical parameters, namely their ratio hs/Rc=(shell thickness)/(core radius). It was observed that the GaAs NW excitonic
emission redshifts almost linearly with the hs/Rc ratio and by up to ~12 meV for hs/Rc=3.6 (ref 6). A similar result was reported for
MBE grown GaAs-Al0.35Ga0.65As core-shell NWs [7], Furthermore, the NW excitonic energy position was compared with the strainshifted values of heavy- and light-hole excitons calculated upon assuming perfect coherence at the GaAs-AlGaAs hetero-interface
and elastic energy equilibrium within the nanowire. Good agreement was obtained for hs/Rc<1, the strain-free peak emission being
identified at 1.510 eV, and ascribed to a bound heavy-hole exciton; for hs/Rc>1 additional reshifts (up to ~9 meV) were observed, and
tentatively ascribed to a shell-dependent exciton localization effects.
Nanoepitaxy The MBE growth approach is based on the deposition of InAs sub-critical coverages followed by a post-growth annealing step (to
obtain nucleation of QDs with low densities) on InxGa1-xAs metamorphic buffers (MBs) to redshift the QD emission thanks to the
reduction of QD strain and of band discontinuities. By monitoring the in-situ time evolution of the RHEED pattern in conjunction
with ex-situ AFM measurements, we derived the minimal coverage resulting in 3D island formation. Henceforth, we were able to
discuss the fundamental differences of the sub-critical growth method compared with the Stranski-Krastanow one, also by
considering available theoretical models for three-dimensional growth for the InAs-InGaAs material system. [3]
Morphological properties of these metamorphic nanostructures were studied by AFM, highlighting how the density of QDs can be
controlled in the low-density range. We analyzed the different morphologies of InGaAs surfaces as functions of In content of the
MBs and we studied their effects on QD positioning and on the uniformity of QD distribution (Fig.1).
Optical properties were studied by ensemble PL at 10K and by µ-PL at 4K and single dot emission was detected in the whole range
from 1000 to 1315 nm (Fig.2) for structures grown on In0.15Ga0.85As MBs, allowing to identify most of the excitonic species at the
ground state. The possibility of studying many-particle complexes makes these nanostructures of particular interest also as sources of
single photons, cornerstones for future nanophotonic devices for quantum cryptography and quantum communication
architectures. In conclusion, our results show that the sub-critical QD growth technique can be successfully used to prepare lowdensity InAs QD structures on metamorphic InGaAs buffers and that, based on advanced µPL characterization, these nanostructures
can be effective single photon sources emitting at 1.3 - 1.55 µm at low temperature.
Fig.1 AFM of QDs grown on In0.15Ga0.85As MBs (top)
and on In0.30Ga0.70As MBs (bottom)
Fig.2 µPL QD spectra from structures grown on In0.15Ga0.85As MBs
[1] C.L. Salter, R.M. Stevenson, I. Farrer, C.A. Nicoll, D.A. Ritchie, and A.J. Shields, Nature 465, 594 (2010) ; [2] L. Seravalli, G. Trevisi, P.
Frigeri, D. Rivas, G. Munoz-Matutano, I. Suarez, B. Alen, J. Canet, and J.P. Martinez-Pastor, Appl. Phys. Lett. 98, 173112 (2011) ; [3] L. Seravalli,
G. Trevisi, and P. Frigeri, CrystEngComm 14, 6833 (2012).
Selective growth of InAs Quantum Dots on GaAs driven by As kinetics
Rita Magria, F. Arcipreteb, E. Placidic, M. Fanfonib, A. Balzarottib, F. Patellab
a
Dipartimento di Fisica, Università degli Studi di Modena e Reggio Emilia and Centro S3 CNR - Istituto Nanoscienze,
Modena, Italy
b
Dipartimento di Fisica, Università di Roma “Tor Vergata”,Roma, Italy
c
CNR - Istituto di Struttura della Materia, Roma, Italy
A selective growth of InAs quantum dots (QDs) has been observed which is exclusively related to the As constituent. This
experiment challenges the widespread belief that the As role in the InAs QDs growth is a minor one, being the QDs growth
commonly described as dictated by the dynamics of cations assumed as the rate-limiting species. The selective growth is obtained by
Molecular Beam Epitaxy at temperatures higher than 500◦C and under an high As/In flux ratio, by changing and tuning the direction
of the As flux on a rippled substrate. In these growth conditions the QDs become aligned along only one of the two mound slopes
forming one dimensional lines. To explain the experiment we have developed a new kinetic model that incorporates many new
features such as (i) a different dynamics for cations and anions; (ii) a distinction between the bulk and surface regions of the dot; (iii)
10 a dot surface composition which comes to depend primarily on the growth conditions. We find that the very small As flux gradient
between the two mound slopes ( F / F ~ (1-5)%) originates a cation current flow from one slope to the other, so that the dots can
develop only on one side of the mounds. The current is generated by the inhomogeneity of the cation adatom distribution between the
two sides of the mound and activated by the relatively high temperatures. Our findings shed a new light on the role of the molecular
specie on the growth of compound semiconductor QDs and a comparable behavior is expected for the anions of other III-V and II-VI
compound semiconductors as well.
[1] F. Arciprete, E. Placidi, R. Magri, M. Fanfoni, A. Balzarotti, and F. Patella, ACS Nano 2013, 7, 3868-3875.
Growth Dynamics of GaAs/AlGaAs Quantum dots by Droplet Epitaxy
Droplet epitaxy (DE) [1] is an emerging and powerful MBE growth technique alternative to the commonly used Stranski-Krastanov
approach for the self-assembly of quantum dots (QDs). Strain-free GaAs quantum dots can be grown by DE crystallizing group III
metallic atoms, stored in nanometer scale droplets, with a group V atomic flux. This allows for an independent control over size and
density of the fabricated QDs. However, despite the high level of design control achieved by DE, the details of the growth kinetics of
the DE-QDs is still unclear. Two fundamental aspects of the QD growth kinetics by DE will be here presented: 1) The crystallization
kinetics of a nanometer size Ga droplet in to a QD under As flux 2) The faceting of a DE-QD and its dependence on the growth
parameters.
The crystallization kinetics of the metallic Ga contained in the droplet into GaAs nanocrystals under the As flux is followed step-bystep, investigating the amount and the morphology of the crystallized GaAs in the droplet at different As doses by means of a
combination of selective wet chemical etching and Atomic Force Microscopy (AFM), in a nano-tomography approach. The
crystallization of the Ga in the droplet starts from a ring of GaAs which is formed just after the Ga deposition at the perimeter of the
droplet. This ring acts as nucleation seed for the subsequent QD growth. During the As supply, the ring increases its size at the
expenses of the metallic droplet. The QD growth the proceeds at the contact surface between the liquid Ga and the ring until the
complete depletion of the Ga contained in the droplet.
The control of the faceting of DE-QD is a fundamental aspect for the fabrication of QDs with on-demand density of states and a
reduced electron-phonon interaction. We will show that it is possible to determine, by the control of the crystallization kinetic, the
shape of DE-QDs. The QD shape depends on the Ga diffusion length in the crystallization condition, thus showing a marked
dependence on As pressure and temperature. The facet orientation evolves, by reducing As pressure or increasing substrate
temperature, from {111} facets, exposed at low temperatures and high As presure, towards {311} facets. A model, based on the
effect of the diffusion of the metallic Ga from the droplet during the crystallization step, is able to reproduce the observed
faceting evolution on temperature and As pressure.
[1] N. Koguchi, S. Takahashi, T. Chikyow, J. Crystal Growth 111 (1991) 688
Nano-patterned organic heterostructures through organic droplet epitaxy
Luisa Raimondoa, Marcello Campioneb, Alessandro Borghesia, Adele Sassellaa
a
Dipartimento di Scienza dei Materiali, Università degli Studi di Milano-Bicocca, Milano, Italy
b
Dipartimento di Scienze dell'Ambiente e del Territorio e di Scienze della Terra, Università degli Studi di MilanoBicocca, Milano, Italy
Nano-epitaxy is a well-established research topic in the framework of inorganic semiconductors based technology. The growth of
nano-objects with well-controlled and defined shape and size allows to develop advanced materials displaying distinguishing
physical properties with respect to the bulk ones. In this respect, organic materials could offer several advantages with respect to
inorganic ones due to their versatility in terms of organic synthesis and molecular self-assembly, but organic nano-epitaxy is not yet
fully developed.
Here, we present an innovative patterning method of organic semiconductors which exploits the mechanisms of organic epitaxy. This
technique is called “organic droplet epitaxy” [1], being a first demonstration in the processing of organic semiconductors of the well
established “droplet epitaxy” method, known for conventional semiconductors [2]. We show that by starting from a first layer made
of amorphous droplets of an organic semiconductor, the deposition of a second material makes droplets undergo crystallization on
11 Nanoepitaxy Stefano Sanguinettia, S. Biettia, C. Somaschinia, A. Fedorovb
a
L-NESS and Dip. di Scienza dei Materiali, Università di Milano Bicocca, Milano, Italy
b
IFN-CNR, Como, Italy
top of the first one, leaving submicrometric holes in the original droplet positions and giving rise to a densely hollowed structure. We
demonstrate that the driving forces for obtaining crystalline nano-patterned organic heterostructures, with sharp and epitaxial
interfaces, are the unbalance of the interface forces for inducing droplet instability, and organic epitaxy between the two materials
involved.
Nanoepitaxy [1] Sassella A., Raimondo L., et al., Adv. Mater 2013, 25, 2804 ; [2] Huang S., Niu Z., et al., Appl. Phys. Lett. 2006, 89, 031921.
12 III-V materials engineering and novel approaches to material deposition for high efficiency Photovoltaics
Gianluca Timò
Ricerca sul Sistema Energetico – RSE S.p.A.
Casino Mandelli, Località Le Mose, Strada torre della razza , 29122 Piacenza, Italy
Email: [email protected]
Engineered Photoanodes for High Efficiency Dye - and Quantum Dot - Sensitized Solar Cells
Isabella Concinaa,b, Gurpreet Singh Selopala,b, Riccardo Milana,b, Alberto Vomieroa,b, Giorgio Sberveglieria,b
a
SENSOR Lab CNR INO, Brescia, Italy
b
SENSOR Lab, University of Brescia, Brescia, Italy
The typical photoanode in dye- and quantum dot- sensitized solar cells is composed of a wide band gap semiconductor, which acts as
electron transporter for the photoelectrochemical system. Anatase TiO2 nanoparticles are one of the most used oxides and are able to
deliver the highest photoconversion efficiency in this kind of solar cells, but intense research in the last years was also addressed to
ZnO and other composite systems. Modulation of the composition and shape of nanostructured photoanodes is key element to tailor
the physical chemical processes regulating charge dynamics and, ultimately, to boost the efficiency of the end user device, by
favoring charge transport and collection, while reducing charge recombination. We investigated several systems: (i) TiO2
nanoparticles / ZnO nanowires [1]; (ii) Multiwall carbon nanotubes (MWCNTs) / TiO2 nanoparticles; (iii) TiO2 nanotubes [2]; (iv)
Hierarchically self-assembled ZnO sub-microstructures [3]. Both dye molecules and semiconducting quantum dots were applied as
light harvesters. Possible tailoring of structure and morphology of the photoanodes, and their implication in improving the functional
properties of these kinds of excitonic solar cells will be discussed in detail.
[1] A. Vomiero, I. Concina, M.M. Natile, E. Comini, G. Faglia, M. Ferroni, I. Kholmanov, G. Sberveglieri, Applied Physics Letters2009, 95, 19310 ;
[2] A. Vomiero, V. Galstyan, A. Braga, I. Concina, M. Brisotto, E. Bontempi, G. Sberveglieri, Energy and Environmental Science 2011, 4, 3408 ; [3]
N. Memarian, I. Concina, A. Braga, S. M. Rozati, A. Vomiero, G. Sberveglieri, Angewandte Chemie In Ed 2011, 50, 12321.
13 Material engineering for PhotoVoltaic conversion in the world of 1 S/W silicon panels While the continuous cost reduction of silicon photovoltaic technology has not been accompanied by a substantial solar cell
efficiency improvement, several different technological approaches have been successfully implemented in the last five years on
III-V multi-junction solar cells. These different approaches have allowed incrementing the solar cell efficiency values of one point by
year, till recently arriving to touch on the 45% value. Starting from the device design principle which characterize the III-V based
multi-junction solar cells, with this contribution, a review of the most important solar cell technologies, and related growth
approaches, from the conventional InGaP/InGaAs/Ge one to the more advanced ones are presented. In particular, the metamorphic
cell (MMC), the inverted metamorphic cell (IMMC), the bifacial solar cell (BFC), the Adjustable Spectrum Lattice Matched (ASLAM) cell, the quantum well solar cells (QWC) and the mechanically stacked solar cells (MSC) are described and compared. In
the frame of the recently concluded FP7 European large integrated APOLLON project, a novel approach to material deposition has
been identified by RSE for further incrementing the solar cell efficiency. This new technological route, which will allow expanding
the combination of semiconductors materials to be used in the MJ cell structures with the potentiality to reach devices with 47%
efficiency value, will be finally presented.
Chalcopyrite based solar materials grown by vacuum and non-vacuum methods
Material engineering for PhotoVoltaic conversion in the world of 1 S/W silicon panels Alessia Le Donnea, S. Marchionnab, P. Garattinia, S. Tombolatoa, B. Vodopiveca, M. Acciarria and S. Binettia
a
De partment of Materials Science and Solar Energy Research Center (MIB-SOLAR),University of Milano-Bicocca,
Via Cozzi 53, Milan (Italy)
b
RSE S.p.A., Via R. Rubattino 54, Milan (Italy)
The development of photovoltaic (PV) absorbers other than silicon proper for thin films based devices has become fundamental in
the last decades to reduce the PV manufacturing costs. Cu(In, Ga)Se2 (CIGS) is nowadays the most promising material for thin film
solar cells, due to the high efficiencies so far obtained [1]. However, the low availability in the Earth crust of Indium and Gallium
(which will lead to a progressive increase of their cost) will constrain the further development of CIGS-based PV devices [2].
A possible alternative to CIGS is Cu2ZnSnS4 (CZTS), where more abundant and less expensive elements like Zn and Sn are used in
place of In and Ga [3]. CZTS can be synthesized through solid state chemical reactions of ZnS, Cu2S, and SnS2, secondary phases
being likely to occur as a consequence of the rather small existence region of single phase CZTS [4]. CZTS, whose most stable
crystalline form is kesterite, has a direct band gap of 1.4-1.5 eV and high absorption coefficient (over 104 cm-1) [5]. The low
formation energy of many of the acceptor defects present in CZTS matrix lead to an intrinsic p-type character, in particular attributed
to the CuZn antisite [6]. Incidentally, being a p-type semiconductor, thin film solar cells based on CZTS can adopt the wellestablished CIGS device structure [1].
This work will report the study of the structural, optical and electrical properties of CZTS thin films grown both by vacuum and nonvacuum methods. The vacuum approach is based on a two step process where metal precursors deposited on Mo coated soda lime
glasses by RF sputtering were sulphurized by thermal treatment in sulphur vapours at 550°C. As far as non-vacuum methods are
concerned, two different approaches have been considered. In the first one, copper sulphide, zinc sulphide and tin sulphide were
prepared as nanoparticles by common chemical reactions and then treated at 600°C in sulphur atmosphere until a micrometric size is
reached. CZTS microparticles were then deposited on Mo-coated substrates by drop casting. In the second non-vacuum method, a
simple dip-coating approach based on the principles of metal-ligand coordination has been used. The precursor solution was prepared
by dissolving copper acetate, zinc acetate and tin chloride in methanol. Thiourea was then added to form the colourless metal-ligand
complex. The solution was then dip-coated several times on Mo coated soda lime glasses, the layers being treated at 220˚C in air for
10 minutes after each deposition. The films were finally annealed in argon flux at 450˚C for 4 hours to remove any organic residual.
To optimize the different growth processes, comprehensive structural characterization (by electron microscopy, Raman spectroscopy
and X-ray diffraction) of the CZTS films has been performed. In particular, both the presence and nature of secondary phases and
point defects have been investigated by Raman and photoluminescence spectroscopies, respectively. Of the many CZTS layers
obtained by the different considered methods, the best PV devices has been obtained using as absorber Cu-poor/Zn-rich CZTS films
grown by the vacuum approach (efficiency around 4%) [7]. Promising results in terms of material quality have been reached with the
non-vacuum methods too, which are compatible with flexible low cost substrates matching the requirements for Building Integrated
PV systems.
[1] P. Jackson et al., Prog. in PV: Res. Appl. 19 (2011) 894 ; [2] C.S.Tao et al., Sol.En.Mat.&Sol.Cells 95 (2011) 3176 ; [3] H. Katagiri et al., Thin
Sol. Films 517 (2009) 2455 ; [4] S. Chen et al., Appl. Phys. Lett. 94 (2009) 041903 ; [5] K. Ito, T. Nakazawa, J. Jo. Appl. Phys. 27 (1988) 2094 ; [6]
S. Chen et al., Phys.Rev. B 81 (2010) 245204 ; [7] S. Marchionna, et al., Thin Solid Films (2013), http://dx.doi.org/10.1016/j.tsf.2013.06.084
A Novel High Load Cvd Reactor For Photovoltaic Applications
Maurizio Masi, Carlo Cavallotti, Diego Boccalari, Francesco Castellana
Dipartimento di Chimica, Materiali e Ingegneria Chimica “Giulio Natta”,Politecnico di Milano, Italy
Among all the renewable primary source of energy a keynote leadership is recognized to photovoltaic technology [1]. Unfortunately,
the cost of the electric energy produced by any of the today available PV technologies is for the moment not competitive with that of
the traditional not renewable ones. In the road map for energy production cost decreasing, one promising technology is to deposit a Si
film on a low cost Si substrate, like a metallurgical grade tile or a polycrystalline wafer. Because of the poor properties of these
substrates, the required film thickness is rather high (e.g. greater than 20 m [2-4]).
Besides the problems inherent to the photovoltaic cell performances (i.e., about 15% conversion efficiency), the key step in term of
cost effective manufacturing is in the hands of the equipment producers who need to offer a deposition reactor with performances not
today existing among the CVD reactors for epitaxial silicon, like a uniformity below 20% on a 20 m film, a cost of ownership
around 1-3 USD for a 8” wafer and a productivity in the order of 1-2 m2/h (i.e., about 40x8” wafer/h).
Because of the “cost impact” of vacuum systems and the standard recipes usually adopted in Si epitaxy, the attention was here
devoted to atmospheric reactors using SiHCl3 or a SIH4/HCl mixture to suppress the formation of powders by homogeneous
nucleation [5]. The here proposed solution is a parallel plate stack reactor operating in alternated inverted flow, whose sketch is
illustrated in Figure 1. The reactor is a hot wall tube containing a removable boat (the susceptor) holding the wafers. The wafers are
placed “vertically” and parallel to the gas flow. Thus, the fluid dynamics configuration is that of several hot wall reactors placed “in
14 parallel” one to the others. In front of the susceptor boat it is realized an inlet chamber aimed to uniformly distribute the gas within
the deposition chambers. This chamber receives the gas feeding jets and provides the exhaust hole. Two of these chambers are
symmetrically placed in the front and in the rear of the reactor. In the first half of the deposition cycle, the inlets are activated in the
front chamber while the outlet is activated in the rear one. The opposite is realized in the second half of the deposition cycle. This
alternating operation allows a satisfactory uniformity even at the highest precursor depletion required to minimize of the cost of
ownership. The reactor was designed through a multi-hierarchy model procedure involving a cascade of models of different
complexity, ranging from very simple one based on analytical solutions to 3D ones solved by CFD methods [5,6].
12
in
in
GR [μm/min]
10
out
8
GR 1° cycle
6
GR 2° cycle
GR total
4
2
in
closed
0
0
0.2
0.4
0.6
0.8
1
susceptor [m]
1.2
1.4
1.6
1.8
Fig. 1. Sketch of the proposed reactor and of the calculated growth rate (1st and 2nd cycle, and average)
[1] R. E. Smalley, MRS Bulletin, 30, 2005, , 412-XXX ; [2] V. Depauwa, I. Gordona, G. Beaucarnea, J. Poortmansa, R. Mertensa, J.-P. Celis,
Materials Science and Engineering B, 159–160, 2009, 286–290 ; [3] A. Focsa, I. Gordon, G. Beaucarne, O. Tuzun, A. Slaoui, J. Poortmans, Thin
Solid Films, 516, 2008, 6896–6901 ; [4] M. Moshlehi, WO2008/070266A2 ; [5] A. Veneroni, M. Masi, Chem. Vap. Deposition, 12, 2006, 562-568 ;
[6] M. Di Stanislao, G. Valente, S. Fascella, C. Spampinato, M. Masi, S. Carrà, J.Phys. IV France, 12, 2002, Pr4-121 – Pr4-128.
Key Developments in CIGS Thin Film Solar Cells on Ceramic Substrates
Alessio Bosio, Daniele Menossi, Greta Rosa, Nicola Romeo
Thin Film Laboratory, Physics and Earth Science Department University of Parma, Viale delle Scienze 7A, 43124 Parma, Italy
Nowadays the improvement of the photovoltaic architectonic integration (BIPV) has become very important. In fact, more emphasis
has been put on the possibility of producing photovoltaic modules able to be integrated, or even to be directly assembled to form the
so-called ventilated walls for buildings. This integration can be improved by using, alternatively to glass, other materials for the
substrate or for the final “box”, in which the solar cells are encapsulated. For example, a good candidate as a substrate material that
substitutes the glass is ceramic. This kind of non-transparent substrates is useful in the substrate configuration solar cell technology,
where the Sun light doesn’t go through the substrate, but comes from the opposite side.
An example of this technology is represented by the Cu(In,Ga)Se2-based solar cells. The challenge in this field corresponds to
directly use, as a substrate, large dimension ceramic tiles which are commercially available on the market. For this reason, the
process technology developed in ThiFiLab for glass substrates has been transferred on this new kind of substrates and some solar
cells have been produced.
Here we present the process developed on these unusual substrates, highlighting the technological innovations made with respect to
the state of the art, that have made possible to achieve photovoltaic energy conversion efficiencies in the range from 12% to 14%
with 5 cm2 CIGS-based solar cells on ceramic substrates.
Low temperature fabrication of 15%-efficient solar cells based on Cu(In,Ga)Se2 films by Pulsed Electron
Deposition technique
Matteo Bronzonia, Filippo Annonia, Francesco Bissolia, Marco Calicchioa, John Paul Garciaa, Edmondo Giliolia,
Francesco Pattinia, Stefano Rampinoa, Vimalkumar Thottapuratha, Massimo Mazzera
15 Material engineering for PhotoVoltaic conversion in the world of 1 S/W silicon panels 14
a
Material engineering for PhotoVoltaic conversion in the world of 1 S/W silicon panels We describe a novel route to low-cost production of Cu(In,Ga)Se2 (CIGS) solar cells based on Pulsed Electron Deposition (PED)
technique: the CIGS absorber layer is deposited in a single step by using a stoichiometric quaternary target, without needing any
selenization treatment nor further cation adjustment [1]. Due to the high energy of evaporating atoms in PED technique, high quality
CIGS films can be grown even at low substrate temperature (< 300 °C), allowing the employment of flexible and low-melting
substrates, as metal or plastic sheets. The p-type conduction of CIGS is finely controlled by growing a NaF film by PED prior or
during the absorber deposition. Photovoltaic efficiencies exceeding 15% have been obtained on lab-scale devices, proving that PED
is a promising technology for a competitive low-temperature fabrication process of CIGS solar cells.
[1] Rampino S., Bronzoni M., et al., Applied Physics Letters 2012, 101, 132107.
16 OFETs architectures to sensing biomolecules interactions
Luisa Torsi
Department of Chemistry, University of Bari A. Moro, Via Orabona 4, Bari, 70126, Italy
17 Organic and hybrid materials Electronic detection of biologically relevant species performed by means of disposable organic devices has the potential to
revolutionize the current approach to strip testing. Bio-systems interfaced to an electronic device is presently one of the most
challenging research activity that has relevance not only for fundamental studies but also for the development of highly performing
bio-sensors. Completely novel approaches either involving OFET devices comprising a Functional Biological Interlayer (FBI-OFET)
or Electrolyte gated-OFET (EGOFET) integrating bio-recognition elements were recently proposed. Specifically, in the FBI-OFET
device configuration a biological layer, acting as biosensor recognition element, is fully integrated into the device structure, residing
underneath the organic semiconductor film, right at the interface were the OFET two-dimensional transport occurs. While in the
EGOFET structure the bio-recognition layer is deposited directly on the organic semiconductor using a strategy that allows a welloriented immobilization of the biological molecules. Both the structures have been successfully employed for the detection of
biological molecules reaching very low detection limits (few part per trillion concentration range). The specific features of each
configuration as well as their performances in terms of device operation, selectivity and sensitivity will be presented. The proposed
bio-electronic FBI-OFET platform, besides resulting in extremely performing biosensors, can open to gather insights into biological
relevant phenomena involving interfacial modifications that can be electronically detected.
Polymorphism-driven functionalities in thieno(bis)imide organic semiconductors
Organic and hybrid materials Margherita Durso,a Cristian Bettini,b Massimo Gazzano, a Denis Gentili, c Massimiliano Cavallini,c Federico Gallino,d
Stefano Toffanin,c Raffella Capelli, c Michele Muccini, c,e Manuela Meluccia
a
Istituto per la Sintesi Organica e la Fotoreattività, (CNR-ISOF), via Gobetti 101, 40129 Bologna, Italy
b
Laboratorio MIST E-R, via P. Gobetti 101, 40129 Bologna, Italy.
c
Istituto per lo Studio dei Materiali Nanostrutturati (CNR-ISMN), via Gobetti 101, 40129 Bologna, Italy
d
SAES Getters S.p.A., Viale Italia, 77, 20020 Lainate - MI - Italy
e
E.T.C. s.r.l., via Gobetti 101, 40129 Bologna, Italy
Thieno(bis)imide (TBI) based oligothiophenes (NTxN) are new multifunctional materials showing unique self-assembly and charge
transport properties. [1] Combined ambipolar charge transport and electroluminescence have been reported for several NTxN
materials. [2] Molecular tailoring and control over the thin film morphology of these materials are subject of great interest for their
applications in organic electronics (i.e. in field-effect transistors (OFETs)[1,3] and light-emitting transistors (OLETs), [2]) to new
types of functional devices such as time-temperature integrator (TTI). [4]
Due to the peculiar structure and electronic features of the TBI group having three different heteroatoms (S,O,N) in a fused aromatic
heterocycle, TBI based systems are characterized by several crystal packing possibilities.
In this communication, we describe how the peculiar polymorphism of selected TBI materials strongly affects their optical and
charge transport properties. We show that ambipolar vs unipolar charge transport in polymorphic NT4N mainly depends on the
different molecular packing motif adopted by NT4N molecules in thin films. In addition, we demonstrate that thermally interconvertible NT3N polymorphic crystals obtained by solution cast, show green or yellow fluorescence depending on the crystalline
packing, this habilitating the fabrication of the first polymorphism based TTI.
[1] M. Durso, D. Gentili, et al., Chem. Commun. 2013, 49, 4298 ; [2] M. Melucci, et al., Chem. Mater. 2013, 25, 668 ; [3] M. Durso, C. Bettini et al
Org. Electr., 2013, doi /10.1016 ; [4] D. Gentili, M. Durso, et al., Scientific Reports , 2013, doi:10.1038/srep02581
Stamp assisted crystal growth for new technological applications
Massimiliano Cavallinia, Denis Gentilia, Fabiola Lisciob, Laura Ferlautob,Margherita Dursoc, Manuela Meluccic
a
ISMN-CNR, Bologna, Italy
b
IMM-CNR, Bologna, Italy
c
ISOF-CNR, Bologna, Italy
In many fields of technology such as organic electronic and organic magnetism (e.g. spin-crossover), the best performances of
devices were demonstrated using single crystals as active materials. De facto a lot of materials have suitable performance only in
crystalline form. Despite the progress, which has been obtained in the fabrication of single crystal devices by various methods, such
as solution growth of aligned organic single crystals[1] or the deposition by ink-jet printing combined with anti-solvent
precipitation,[2] the possibilities to process single crystals are limited by the nature of the materials and their capability to crystallize.
Usually, the devices are fabricated around the single crystal by placing, or evaporating, the electrodes on to it, otherwise the crystals
are grown by drop casting on to prefabricated devices without control over position and orientation, limiting the large-area
application and the up-scaling of this technology.
In order to address these problems, we used lithographically controlled wetting (LCW), which is an elegant and easy wet-lithographic
method that exploits the self-organising properties of the functional materials to create highly-reproducible nanopatterns with
precisely controlled dimensions.[3] LCW has proven to be a powerful tool for the manipulation of soluble organic compounds in predefined structures, and allowed to improve their crystallinity, their electrical properties [4] and, in some cases, to drive crystal
orientation.[5] We show how the patterning of crystals opens new perspectives for the applications in nanoelectronic and in some
cases the patterning opens new unexpected possible applications such as in time temperature integrators[7], also exploiting unwanted
properties as polymorphism,[8] of a wide range of materials.
[1] M. Watanabe, Y. J. Chang, S. W. Liu, T. H. Chao, K. Goto, M. M. Islam, C. H. Yuan, Y. T. Tao, T. Shinmyozu, T. J. Chow, Nat. Chem. 2012, 4,
574 ; [2] H. Minemawari, T. Yamada, H. Matsui, J. Tsutsumi, S. Haas, R. Chiba, R. Kumai, T. Hasegawa, Nature 2011, 475, 364 ; [3] M. Cavallini,
C. Albonetti, F. Biscarini, Adv. Mater. 2009, 21, 1043 ; [4] M. Cavallini, D. Gentili, P. Greco, F. Valle, F. Biscarini, Nat. Protoc. 2012, 7, 1569 ; [5]
M. Cavallini, P. D'Angelo, V. V. Criado, D. Gentili, A. Shehu, F. Leonardi, S. Milita, F. Liscio, F. Biscarini, Advanced Materials 2011, 23, 5091 ; [6]
M. Cavallini, A. Calo, P. Stoliar, J. C. Kengne, S. Martins, F. C. Matacotta, F. Quist, G. Gbabode, N. Dumont, Y. H. Geerts, F. Biscarini, Adv. Mater.
2009, 21, 4688 ; [7] M. Cavallini, I. Bergenti, S. Milita, G. Ruani, I. Salitros, Z. R. Qu, R. Chandrasekar, M. Ruben, Angew. Chem.-In. Ed. 2008, 47,
8596 ; [8] D. Gentili, M. Durso, C. Bettini, I. Manet, M. Gazzano, R. Capelli, M. Muccini, M. Melucci, M. Cavallini, Scientific Reports 2013, 3,
2581.
18 Evidence of the stable alignment of porphyrin tautomers, following an unconventional organic film growth
Gianlorenzo Bussettia, Marcello Campioneb, Michele Rivaa, Andrea Piconea, Luisa Raimondob, Lorenzo Ferrarob,
Conor Hoganc, Maurizia Palummod, Alberto Brambillaa, Marco Finazzia, Lamberto Duòa, Adele Sassellab, Franco
Ciccaccia
a
Politecnico di Milano, Milano, Italy
b
Università Milano-Bicocca, Milano, Italy
c
ISM-CNR, Roma, Italy
d
Univaristà Tor Vergata, Roma, Italy
[1] Jurow M., Schuckman A. E., et al., Coord. Chem. Rev. 2010, 254, 19 ; [2] Auwärter W., et al., Nature Nanotech. 2011, 7, 41 ; [3] Bussetti G.,
Campione M., et al., Adv. Funct. Mater. 2013, DOI:10.1002/adfm.201301892
Self-assembly of Glutamic acid at Ag surfaces: understanding the bio-interface at the nanoscopic level.
Letizia Savio1*, M. Smerieri12, L. Vattuone12, M. Rocca12 I. Tranca3, D. Costa4, F. Tielens3
1
IMEM-CNR, Via Dodecaneso 33, 16146 Genova, Italy
2
Dipartimento di Fisica, Via Dodecaneso 33, 16146 Genova, Italy
3
UPMC Univ Paris 06, UMR 7197, and CNRS, UMR 7609, Laboratoire de Réactivité de Surface,
8 rue Galilée, F-94200 Ivry-Sur-Seine, France
4
Laboratoire de Physico-Chimie des Surfaces, ENSCP, ParisTech,
11 rue P. et M. Curie, F-75005 Paris, France
The understanding of the interactions between biomolecules and metal/oxide surfaces is mandatory for all those applications in
which this interaction wants to be either exploited (biomaterials, nanoelectronics, hybrid material design) or avoided (fouling,
hygiene). The huge experimental effort in this field was however so far insufficient for a complete understanding of the complex biomolecule/surface interactions at the molecular level. Model experiments and computations are thus mandatory.
Amino acids (AA) are protagonists of fundamental studies, since they are the basic constituents of peptides and proteins and are
simple enough to bring information on the chemical interaction of some biological functions with the surface.
We report here on the interaction of (S)-Glutamic Acid (Glu) with LMI Ag surfaces in the temperature range 250 K<T<400 K,
investigated by experimental and theoretical methods. Glu molecules self-assemble in different geometries, depending on the
substrate and on the deposition temperature, and adsorb always in the non-zwittterionic form [1-4], at variance with the majority of
cases reported in literature and with what expected for analogy with other AA adsorbed on Ag(111) [5].
On Ag(100) four different structures form depending on deposition temperature and thermal treatments [2]. Two of them, namely the
“square” and the “flower” assemblies (coexisting at 350 K – see figure) have been fully resolved at the molecular level by a careful
combination of STM, HREELS and XPS results and of ab-initio DFT calculations. We were able to unravel the details of the selfassembled layer and the driving mechanisms of the self-assembly process and thus to describe the organic-hynorganic interface to an
unprecedented degree of details for sytems of comparable complexity.
[1] M. Smerieri, L. Vattuone, D. Costa, F. Tielens, L. Savio, Langmuir 26, 7208 (2010) ; [2] M. Smerieri, L. Vattuone, T. Kravchuk, D. Costa, L.
Savio, Langmuir 27, 2393 (2011) ; [3] M. Smerieri, L. Vattuone, M. Rocca, L. Savio, Langmuir 29, 6867 (2013) ; [4] I. Tranca, M. Smerieri, L.Savio,
L. Vattuone,D. Costa, F. Tielens, Langmuir 29, 7876 (2013) ; [5] J. Reichert et al., ACS Nano 4, 1218 (2010).
19 Organic and hybrid materials Porphyrins and porphyrinic compounds are used as building blocks in organic electronic devices, such as switches, memories,
spectroscopic markers, solar cells, sensors, tailored molecular catalysts, engineered molecular nanostructures or molecular
spintronics [1]. Recently, both research and very first applications have also focused interest on the intra-molecular physicalchemical processes of porphyrins, such as the tautomer mechanism [2], in view of exploiting the single molecule properties.
Tautomerization in free base porphyrins - a process involving the exchange of two inner protons (hydrogen) between the nitrogen
atoms - has been extensively studied at very low temperatures (down to 6 K), where this chemical reaction is not active anymore.
However, the conditions needed for a stable tautomer clearly represent a severe drawback for obtaining a charge storage for
electronic applications [2].
Recently, we obtained a genuine porphyrin (namely H2TPP) single layer, following an unconventional film growth. A combined
scanning tunneling microscopy (STM) and reflectance anisotropy spectroscopy (RAS) experiment proves that, even at room
temperature, tautomerization is not active in this system. Theoretical simulations (accepted ETSF proposal) fully support our findings
and demonstrate the mechanism of the porphyrin tautomer freezing.
On this basis we are able to propose a new way of exploiting uniaxially oriented H2TPP tautomers in a first elementary logic device
prototype [3].
Organic and hybrid materials Fig. 1. STM images of the flower and square layers forming upon Glu deposition on Ag(100) and corresponding calculated structures.
Single crystalline rubrene: the organic silicon
Marcello Campioneb, Silvia Trabattonia, Enrico Fumagallia, Luisa Raimondoa, Massimo Moreta, Adele Sassellaa
a
b
The success and supremacy of silicon based microelectronics is mainly due to the possibility to grow this semiconductor in large and
pure single crystals and to its reaction with oxygen giving rise to an insulating layer of silicon oxide with controlled properties. The
recent huge interest on organic semiconductors is aimed at developing an alternative technology having cost effectiveness together
with additional prerogatives such as the use of flexible matrixes hosting the active semiconducting layer. Even if the research
community on organic semiconductors is aware that the performances of organic based devices will unlikely equate those of
inorganic semiconductors, some small molecule semiconductors have shown impressive properties in terms of charge carrier
mobility and electroluminescence. Among these materials, the orthorhombic polymorph of rubrene has shown to possess a record
hole mobility, making rubrene itself the most promising member of its class of materials. However, the processing of rubrene is
associated to important issues that hinder its establishment as reference benchmark for organic semiconducting devices. The most
important one is its spontaneous solidification in an amorphous state when processed as thin film, and the rapid oxidation of this
phase. We solved this major issue by developing an epitaxial strategy for the growth of crystalline and oriented thin films of rubrene.
We focus here on the interesting observation of the growth of a native oxide layer on the surface of these films. Previous
investigations have shown that this layer grows through the migration of molecules at step-edges towards the top terraces, covering
uniformly the film surface with a thickness of ca. 2 nm. This oxide layer is known to have a slight difference in the out-of-plane
spacing with respect to orthorhombic rubrene and to induce changes of the surface potential. However, its structure is still unknown.
Here, we succeeded in isolating a crystalline orthorhombic phase of rubrene endoperoxide by solution processing. This phase shows
an almost perfect coincidence of lattice parameters with those of rubrene. Then, the oxide layer is crystalline and commensurate with
the semiconductor, explaining why the oxidation of rubrene is spontaneous and brings about the formation of ordered layers. This
finding opens an interesting scenario since, similarly to silicon, the insulating oxide layer of a good semiconductor can be exploited
for fabricating complex microlectronic devices.
Charge trapping on metal nanoparticles in an organic semiconductor matrix and light-induced detrapping
Giovanni Ligorioa, Marco Vittorio Nardia, Christos Christodouloua, Martin Brinkmannb, Marc Schmutzb, and Norbert
Kocha, c
a
Humboldt-Universität zu Berlin, Institut für Physik. Brook-Taylor-Str. 6, 12489, Berlin, Germany
b
Institut Charles Sadron CNRS, rue du loess 22, 67034 Strasbourg, France
c
Helmholtz Zentrum Berlin für Materialien und Energie. Albert-Einstein-Straße 15, 12489, Berlin, Germany
As an emerging area in organic electronics, nonvolatile memories (NVMs) have become an active research topic in recent years,
20 [1] L.D. Bozano, et. al., Applied Physics Letters 84, 607 (2004) ; [2] L. Ma, et. al., Applied Physics Letters 82, 1419 (2003).
Bias Stress effects in n-type organic single-crystal and thin-film transistors
Mario Barra
CNR-SPIN and Dep. of Physics Science, University of Naples, Piazzale Tecchio 80, Naples Italy
The bias stress (BS) phenomenon is the main source of operational instability in the organic field-effect transistors (OFET) and
represents the most serious obstacle to their commercial introduction [1]. This effect, which main evidence is the continuous time
decay of the drain-source (IDS) current when the transistors are driven in the accumulation regime for a prolonged time, has been
widely investigated for p-channel OFET. Conversely, for n-channel transistors, it has so far received little attention and few
experimental data are currently available. This contribution deals with a wide analysis about the occurrence of the BS effects in ntype OFET with active channels based on Perylene diimide molecules functionalized with cyano groups in the bay region, namely
PDI8-CN2 and PDIF-CN2. These compounds are still today among the most interesting n-type semiconducting compounds thanks to
their highly robust charge transport properties under ambient conditions [2].
In this work, the influence of both morphological and organic/dielectric interfacial effects on BS phenomena were investigated by
taking into consideration single-crystal [3] and thin-film devices, with these latter achieved employing both evaporation [4] and
inkjet-printing techniques [5].When the BS effect was analyzed in PDIF-CN2 single-crystal transistors with Cytop gate dielectric, the
amount of stress was found to be very small, with performances overcoming those of all (p-channel) organic transistors studied in the
past. In particular, we observe that in vacuum the BS effect in these devices tends to saturate over periods larger than 1-2 days, while
in air, IDS(t) decreases by only 10% even when they are driven in the accumulation regime for an entire week. On the other hand, the
experimental data concerning PDI8-CN2 thin-film devices fabricated by evaporation and inkjet-printing techniques demonstrate that
the chemical properties of the interface between dielectric barrier and semiconductor play a major role in the BS effect, prompting
for the possibility that its physical origin is mainly related to the occurrence of electrochemical reactions involving water, oxygen and
free charge carriers. These results highlight also that, when the devices are operated in the depletion regime (under the application of
negative VGS voltages), the physical processes ruling BS in the accumulation regime can provide a fast enhancement of the drainsource current flowing in the active channel. This effect was never reported and discussed before.
In conclusions, although n-type OFET have been traditionally considered to be more sensitive on charge trapping process, this study
outlines that a right combination of materials allows highly controlling the BS effect in these devices.
[1] H. Sirringhaus, Adv. Mater. 21, (2009) 3859 ; [2] B. A. Jones, A. Facchetti, M. R. Wasielewski, T. J. Marks, J. Am. Chem. Soc. 129, (2007)
15259 ; [3] M. Barra, F. V. Di Girolamo, N. A. Minder, I. Gutierrez-Lezama, Z. Chen, A. Facchetti, A. F. Morpurgo, A. Cassinese, Applied Physics
Letters 100, (20012) 133301 ; [4] F.V. Di Girolamo, F. Ciccullo, M. Barra, A. Carella, A. Cassinese, Organic Electronics 11, (2012) 2281 ; [5] I.A.
Grimaldi, M. Barra, A. Carella, F.V. Di Girolamo, F. Loffredo, C. Minarini, F. Villani, A. Cassinese, Synthetic Metals 15, (2013) 121.
21 Organic and hybrid materials because they are likely to be an alternative or supplementary technology to the conventional memory. Among the different typology
of NVMs, resistive switching devices (R-NVMs) are promising for their simple structure and easy processability. A typical structure
of such resistive switching device is a hybrid structure organic/inorganic, i.e. metal nanoparticles (M-NPs) embedded in organic
layers, between two electrodes. The switching between the high resistance state (OFF state) and the low resistance state (ON state) is
usually achieved by a specific threshold electrical stimulus. NPs charging/discharging with consequent interaction with the charge
carriers through the device have been often attributed as switching mechanism [1], [2].
Optical addressing might be a novel approach to change the charge state of the metal NPs and could allow improving functionality
and reducing writing time.
We used ultraviolet photoelectron spectroscopy (UPS) to investigate charging and light-induced decharging of Au NPs imbedded in a
matrix of organic semiconductors, i.e., aluminum tris(8-hydroxyquinoline) (Alq3) and 4,4-bis[N-(1-naphthyl)-N-phenylamino]diphenyl (α-NPD). Depending on the density and size of Au NPs, as determined by transmission electron microscopy, we find
a reduced photoelectron kinetic energy in dark, indicative of trapping of positive charges on the NPs. Upon light irradiation,
photoelectrons resume the initial higher kinetic energy, evidencing that the charges on the Au NPs can be de-trapped by optical
means. This mechanism may lead to the realization of novel organic/inorganic memory elements.
Functional Magnetic Nanoparticles
Functional nanostructures Alessandro Pontia
a
Istituto di Scienze e Tecnologie Molecolari, Consiglio Nazionale delle Ricerche, via C. Golgi 19, Milano, Italy
In the huge field of nanotechnology and nanoscience, nanoparticles surely are among the most investigated nanosystems because of
their peculiar zero-dimensionality (0-D) which makes them true nano-objects riding the borderline between classical and quantum
behavior. Further, magnetic nanoparticles, i. e., nanoparticles possessing a permanent magnetic moment, have had a prominent share
in the nanoscience since long, an importance that goes on undisputed also in the present times. This interest is due to the many
possible uses of a tiny magnetic moment that can be exploited in fields as diverse as chemistry, materials science, and medicine. It
can be used to drive things around, to heat objects, to visualize otherwise invisible structures, to store information, to stop EM
disturbances and even to enhance tissue regeneration. I will focus on magnetic nanoparticles synthesized by solvothermal methods
which allow one to prepare in a quick and cheap way relatively large (100 mg scale) amounts of inorganic magnetic nanocrystals
with tightly controlled size, shape, and composition. These are the principal factors governing the instrinsic magnetic properties of
the nanocrystals. Solvothermal synthetic methods require that the nanocrystal growth is regulated and that the nanocrystals are
protected from aggregation. Both tasks are carried out by introducing appropriate organic molecules (usually polar head-apolar tail
surfactants) which strongly bind to the nanocrystal surface and forms a self-assembled monolayer (SAM). It is this combination of
inorganic magnetic nanocrystal core and tailored organic molecular coating that I call “nanoparticle”. The organic coating is at least
as important as the nanocrystal in determining the properties and behavior of the nanoparticle. Indeed, the SAM is the interface
between the nanocrystal and the environment, not only has it regulated the nanocrystal growth and protects it from aggregation, it
mediates all interactions of the nanocrystal with the environment, from basic solubility issues to fine recognition processes involving
biochemical targets. Clearly, a magnetic nanoparticles can be considered as the functional combination of magnetic inorganic
nanocrystal and organic coating. For a successful application both nanocrystal and organic coating must provide a functionality
(often more than one!) and these functionalities must act in a synergistic way. Among the many possible applications of magnetic
nanoparticles, I will focus on applications in the biomedical field. Of course, these are the most promising and most expected
applications but the way from the laboratory to the bedside is very long. In particular, I hold important to tackle seemingly trivial
aspects of the potentially useful system – such as the colloidal stability in water – from the very beginning to end up with a robust
nanoproduct. Another extremely important issue is that of nanotoxicology and nanosafety. We do not know much about these effects
and it is at present difficult even to compare results from different labs due to the large diversity of methods, materials, and
biosystems investigated. I will show some examples taken from our own research related to the nanoparticles colloidal stability in
biocompatible aqueous media, the uptake of nanoparticles by phagocytic and non-phagocytic cells, and the immunologic response of
primary human phagocytic cells.
22 Synthesis and Characterization of Iron Oxide Gold Core/Shell Nanoparticles for Cancer Care
Filippo Benettia, Devid Maniglioa, Giorgio Speranzab, Claudio Migliaresia
Department of Industrial Engineering, University of Trento, Italy
b
Fondazione Bruno Kessler, Trento, Italy
a
[1] Lim J., Majetich S. A., Nano Today 2013, 8, 98 ; [2] Zhang X., Wu D., et al., Biomaterials 2012, 33, 6408.
SiO2/SiC core-shell nanowires for nanomedicine applications
G. Salviati1, F. Fabbri1, F. Rossi1, L. Nasi1, M. Campanini5, G. Attolini1, D. Sathish Chander1, M. Negri1, F. Albertini1,
F. Casoli1, V. Chiesi1, R. Verucchi2, L. Aversa1, M. Nardi3, S. Iannotta1, F. Bigi2, E. Bedogni2, L. Cristofolini3, T.
Rimoldi3, P. Petronini4, R. Alfieri4, M. Galetti4, A. Mutti4, M. Goldoni4, R. Alinovi4, A. Cacchioli5, F. Ravanetti5, G.
Benecchi6, C. Ghetti6
1
2
Chemistry Department, Parma University, Italy
3
Department of Physics and Earth Science “M. Melloni”, Parma University, Italy
4
Dept. of Clinical and Experimental Medicine, Parma University, Italy
5
Animal Health Dept, Faculty of Veterinary Medicine, Parma University, Italy
6
Health Physics Department, Parma Hospital. (Italy)
A new two-fold nanosystem exploiting the simultaneous action of oxidative stress generated by self lighted photodynamic therapy
[1] and hyperthermia induced by radiofrequency magnetic fields [2], is presented and discussed in view of possible deep cancer
treatments. The nanosystem is based on CVD grown SiO2/3C-SiC nanowires [3] functionalized with tetraphenylporphyrins via
SuMBD and click-chemistry procedures and superparamagnetic Fe3O4 nanoparticles (NPs) [4].
The SuMBD functionalization, based on a kinetic approach, allowed to clarify the energy transfer mechanisms at the
semiconductor/organic interface while the wet chemistry functionalization has been used to attach to the NWs both the porphiryn and
the superparamagnetic NPs. As for the porphyrin functionalization of the NWs via click-chemistry procedures, it has been
accomplished by introducing complementary groups on the SiO2 surface and in the prophyrin. i.e. azize and alkyne groups
respectively.
Fe3O4 nanoparticles (5< <8 nm) are prepared by thermal decomposition of iron acetylacetonate. The free hydroxy groups of the
SiO2 shell are properly functionalized and then Fe3O4 nanoparticles, after further stabilization (10-undecynoic acid), are grafted onto
the nanowires by exploiting a click-chemistry reaction.
The best superparamagnetic properties are found for 8 nm nanoparticles which present a saturation value of the magnetic moment per
unit volume of 60 emu/gr. The hypertermic properties are measured by applying a radiofrequency magnetic field (f=250KHz
H=0.016 T) in a commercial system, to a colloidal suspension containing the NPs. Then the adiabatic measure of the specimen
temperature variation as a function of time is determined through an optical fiber thermometer. The specific power absorption
(hyperthermia) of the same nanoparticles is around 4.3 W/g, a value which allows the cell to achieve in 1100 sec a final T >41 °C.
To verify the biocompatibility of the nanosystem, after optimizing the functional properties [5,6,7], in-vitro tests on lung and human
breast adenocarcinoma cells and human skin derma fibroblasts are carried out. The influence of concentration (0-100 µg/ml) and
23 Functional nanostructures Compared to the elements normally involved in biological structures, gold presents higher cross-section for the scattering of gamma
rays. The interaction between gold atoms and gamma rays leads to the generation of secondary electrons and photons which can
provoke lethal damages to cells. A large variety of gold nanoparticles have been developed to deliver gold in cancer cells and several
studies have demonstrated the radiosensitizing properties of gold colloids by in vitro and in vivo tests. Iron oxide nanoparticles (FeOx
NPs) have been also widely studied in the last years because FeOx NPs can be used as contrast agents for magnetic resonance
imaging. The aim of the work was to realize an innovative theragnostic nanotool for cancer care based on the radiosensitizing activity
of gold and on the properties of FeOx NPs for imaging. The iron oxide/gold core/shell geometry was chosen because gold surfaces
are easy to functionalize using thiolated polymers to ensure the biomimetic behavior and the biocompatibility of the nanoparticles in
blood environment. A lot of works have faced the problem of core/shell nanoparticles synthesis using different approaches but till
now no efficient protocols have been developed for the fast synthesis of water soluble iron oxide gold core/shell nanoparticles
(AuFeOx NPs) in the size range from 10 to 20 nm which was identified as the best standard for radiotherapy enhancement [1,2]. In
this work a novel method for the AuFeOx NPs synthesis was developed performing the reduction of acid gold on the interface of 7
nm FeOx NPs in presence of thiolated polyethylene glycol (PEG-SH). The polymer molecules were added in the synthesis solution
for binding the gold nucleation sites and preventing the coordination of further gold atoms on the fresh made gold surface. This
mechanism allowed to obtain a thin and homogeneous gold coating on the surface of FeOx NPs. Different PEG-SH concentrations
were tested in order to study the effects of PEG-SH in the process. The optimized AuFeOx NPs were characterized by TEM
revealing a gold shell thickness smaller then few nanometers. UV-visible spectroscopy and ICP-EOS analysis confirmed the presence
of both gold and iron in the AuFeOx NPs solution.
time (up to 72 hrs) on cell proliferation and death is studied. It is found that SiO2/SiC nanowires inhibit cell proliferation and induce
necrosis only at concentrations >50-100 µg/ml. The Fe3O4 nanoparticles do not inhibit cell proliferation and do not induce death up
to 100 µg/ml as well as oxidative stress up to 50 µg/ml.
Preliminary tests on on lung adenocarcinoma cells after porfirinated NWs internalization have been performed at the health Physics
Dept. of the Parma Hospital at 6 MV X-rays in a clinical linear accelerator for radiation therapy (Lynac Varian VHXD). The results
showed a max decrease of 75% of the intracellular triphosphate adenosine (ATP) production after 72 hs from the irradiation.
The aforementioned results demonstrate that the proposed nanosystem can represent an interesting approach for future applications in
cancer treatments.
Functional nanostructures [1] P. Yuzenas, W. Chen et al., Advanced Drug Delivery Reviews 2008, 60, 1600 ; [2] Van der Zee J., Annals of Oncology 2002 13(8), 1173 ; [3] F.
Fabbri, F. Rossi et al. , Materials Letters 2012, 71, 137 ; [4] G. Salviati, F. Fabbri et al., MRS Fall Meeting, 2012, Symp FF ; [5] F. Fabbri, F. Rossi
et al., Nanoscale Research Letters 2012, 7, 680 ; [6] F. Fabbri, F. Rossi et al; Microscopy and Microanalysis 2010, 16(S2), 826 ; [7] F. Fabbri, F.
Rossi et al., Nanotechnology 2010, 21, 345702
Nanosizing Crystalline Diamond Array by a Dual-Mode MW-RF Plasma Reactor
Stefano Gaya, S. Orlanduccia, E. Tamburria, V. Guglielmottia,b, G. Reinaa,b, T. Lavecchiaa, M. L. Terranovaa,b, M.
Rossib,c
a
Università degli Studi di Roma “Tor Vergata”, Roma
b
NanoShare S.r.l., via G. Peroni, Roma
c
Dipartimento di Scienze di Base e Applicate all’Ingegneria CNIS, Università di Roma “Sapienza”, Roma
We are currently working on the nanosizing and shaping of diamond, which is a stringent requirement for advanced electronic
applications. In recent years shaping of single-crystal and polycrystalline diamond to the nanoscale has become a hot topic, leading to
the synthesis of rods and wires with different sizes, diameters and aspect ratio [1],[2]. Nevertheless, the shaping of diamond in
particular forms is not easy and the nanometric control of the morphology and orientation of the diamond units is still a challenging
task. Using a custom-made dual-mode MW-RF plasma reactor in which a radiofrequency is applied to the substrate in the presence
of a MW power, we have developed a reliable methodology able to modify on a nanoscale the features of materials by means of a
controlled temperature H etching (from room temperature to 1000°C) [3]. This communication will illustrate some examples of
nanostructures obtained by this H-etching processes applied during or after the synthesis of diamond. The morphology and structure
of the nanosized layers have been investigated by FE-SEM, micro-Raman and RHEED. Field Emission and Secondary Electron
Emission measurements have also been carried out. Starting from different kind of crystalline films, we obtained nanowires,
nanorods, nanocones and nanowhiskers. The high aspect ratio of such elongated structures is responsible for the high local field
enhancement effect, and the arrays of needle-like diamond behave as templates for an effective electron emitter [4]. Due to the
remarkable properties of diamond, these nanostructures, that retain the crystallographic properties of the diamond, are well suited for
the fabrication of stable and robust cold cathodes, to be used also under harsh working conditions. An increasing interest is also
arising for the use of such nanostructure in the field of bio-medical applications, as attractive scaffolds for tissue growth and for
selective attachment of targeting groups, and for bio-analytical applications.
[1] Chih-Hsun Hsu, et al., Nano Lett., 2010, 10, 3272 ; [2] A. S. Barnard, Rev. Adv. Mater. Sci. 2004, 6, 94 ; [3] S. Orlanducci, et al. Nanoscience
and Nanotechnology Letters 2012, 4, 338 ; [4] S. Orlanducci, et al. 2011 MRS Fall Meeting 2011
Hollandite Nanoparticles for Chemical Sensing: Strain or Pseudosymmetry?
Alice Boschetti, Michele Gregorkiewitz
Dept of Physical, Earth and Environmental Sciences, University of Siena, Italy
Potassium-Hollandite was studied as a semiconductor for conductometric chemical sensors, for its properties to easily change
composition and electronic structure. Samples were synthesised by a hydrothermal method in an autoclave. Rietveld refinement of
the nanocrystalline powders was undertaken in the tetragonal system (space group I4/m) with the purpose to obtain precise
information about atom parameters and grain size. Allowing for the refinement of atom parameters, unit cell and isotropic Lorentzian
and Gaussian peak widths, a roughly acceptable model was obtained for the structure, but the description of the peak shape was
surprisingly unsatisfactory. In fact, the observed widths of diffraction peaks vary from one reflection to another by as much as
δ2θ=0.007 to 0.0026 rad.
This is commonly attributed to either grain shape anisotropy or to the anisotropy of internal tensions. Both, in principle, act in a
different way on the peak width and are therefore distinguishable. The solution offered by modern Rietveld calculation programs in
24 pseudosymmetric structures of nanomaterials.
[1] Larson A.C., Von Dreele R.B., Los Alamos Nat Laboratory Report LAUR 86-748 2004.
[2] Stephens P., J Applied Crystallography 1999, 32, 281.
Hydroquinone based synthesis of Au nanoparticles with shape control for SERS applications
Carlo Morassoa, Dora Mehna, Domitilla Schiumarinia, Renzo Vannaa, Marzia Bedonia, Chiara Pignataria, Davide
Prosperia b, Furio Gramaticaa
a
Fondazione Don Carlo Gnocchi ONLUS, Milan, Italy
b
Università degli Studi di Milano-Bicocca, Milan, Italy
Surface Enhanced Raman Spectroscopy (SERS) is a popular technique in bioanalytical chemistry and a potentially powerful enabling
technology for in vitro diagnostics. In fact, SERS combines the excellent chemical specificity of Raman spectroscopy with the good
sensitivity provided by the enhancement of signals that is observed when the analyzed molecule lies over (or very close to) the
surface of metal nanoparticles [1]. As SERS enhancement strongly depends from the morphology of the metal nanostructures
employed, in the last few years a huge effort has been done by many laboratories to improve the control on shape and dimension of
protocols used to prepare plasmonic nanoparticles [2-3].
Here, we present how hydroquinone can be used as reducing agent for the synthesis of gold nanoparticles in a seed mediated
approach. Using this route we were able to produce spherical, rod-like and star-like [4] structures of different dimensions ranging
from 60 to 120 nm. Moreover it has been possible to improve the standard synthesis of nanorods decreasing of 50% the amount of
CTAB, an expensive and cytotoxic reagent, used.
The different nanoparticles were then compared in order to define the most effective SERS enhancing shape. Star-Like Gold
Nanoparticles (SGNs) result to be the most effective structure, increasing Raman signals 10 to 50 times more than spherical particles.
Based on these data and on their good physicochemical characteristics, we expect that SGNs prepared in this way could be used for
further development of highly specific and sensitive SERS-based assays for the detection of various biomarkers.
[1] Bantz K.C., Meyer A.F., Wittenberg N.J., Im H., Kurtulus O., Lee S.H., Lindquist N.C., Oh S-H., Haynes C. “Recent Progress in SERS
Biosensing” Phys. Chem. Chem. Phys., 2011 (13) 11551-11567 ; [2] Tao A.T., Habas S., Yang P. “Shape Control of Colloidal Metal Nanocrystals”
Small, 2008 (4) 310-325 ; [3] Sau T.K., Rogach A. “Complex-shaped Metal Nanoparticles” 2012 Wiley-VCH Verlag GmbH & Co., Weinheim,
Germany ; [4] Mehn D., Morasso C., Vanna R., Bedoni M., Prosperi D., Gramatica F. “Immobilized gold nanostars in a paper based test system for
Surface Enhanced Raman Spectroscopy” Vibrational Spectroscopy, 2013 (68) 45-50.
25 Functional nanostructures simulating powder patterns is to refine two sets of parameters describing the peak width as a function of microstrain and/or grain size
anisotropy [1,2]. Allowing, in a first step, only for anisotropic grain shape refinement, relatively low error indices (2=1.260,
Rp=0.122, RF2=0.080) could already be achieved, but allowing for microstrain, the refinement result was significantly improved
converging to a model with 2=1.196, Rp=0.117, RF2=0.067. In this model, a prolate rotational ellipsoid grain shape of 88*276A3
was obtained, in agreement with the usually acicular habit of hollandite crystals. The presence of microstrain and its physical
meaning, on the other hand, was much less obvious: indeed, a regression line obtained from the Williamson-Hall plot shows a
negative slope, which is not reasonable for a microstrain value.
A careful inspection of the diffraction pattern shows that some strongly widened peaks suggest a splitting caused by
desymmetrization of the structure. In the present case, hkl+khl+(-h)kl peaks that should be coincident in the tetragonal system would
be separated indicating a descent to monoclinic symmetry. This is also in agreement with some earlier work where monoclinic
symmetry has been found for K-hollandite. Nanomaterials always generate large diffraction peaks which make indistinguishable the
peak-splitting due to pseudosymmetry, so it is detectable but not resolvable at the level of refinement because of the nature of the
material.
For these reasons a new model for the description of anisotropic line-broadening has been developed where pseudosymmetry
(monoclinic<tetragonal for the synthesised K-hollandite) becomes a further cause of anisotropic line-broadening. The nature of the
split, or the peak width (in the case of unresolved splitting, especially for nanomaterials), is quantified starting from the relation for
the interplanar spacing dhkl and introducing two parameters of unit cell variation, one related to a length and the other to an angle.
Through these parameters, we could reproduce the contribution to anisotropic peak broadening caused by symmetry lowering. In
future, it might be interesting to include such contribution, which has a strong hkl dependence similar to the one of microstrain, as
regression parameters in a least squares refinement program for improving the results obtained for both the structure and the grain
size, which is fundamental for material properties but by no means trivial to measure. The new model has been of great importance in
refining the present K-hollandite structure and grain size, and may prove to be of general interest for the refinement of
Nanomedicine: Demands and Challenges
Chair: Salvatore Iannotta
INVITED SPEAKERS:
Furio Gramatica
Fondazione Don Carlo Gnocchi and European Technology Platform Nanomedicine
"Open innovation in Nanomedicine: challenges and achievements towards a real personalized medicine in
Horizon 2020"
Round Table Luisa Torsi
Dipartimento di Chimica, Università degli Studi di Bari "Aldo Moro"
"Advanced materials for bioelectronics"
Stephen E. Saddow
University of South Florida, Tampa, FL (USA), Electrical Engineering Department and Dept. of Molecular
Pharmacology and Physiology
"Biocompatible Semiconductor for Advanced Biomedical Devices and Applications: SiC and Graphene"
Vittorio De Franciscis
Istituto per l’Endocrinologia e Oncologia Sperimentale "G. Salvatore" - IEOS-CNR
"Molecular systems for therapy and diagnostics"
Nicola Fazio
Banca delle Cellule e del Tessuto Muscoloscheletrico dell'Emilia Romagna, Istituto Ortopedico Rizzoli
"Biomaterials in orthopedics: is graphene a novel candidate for bone regeneration?"
DISCUSSION AMONG ALL THE PARTICIPANTS
The round table is the closing event of the Italian Conference on Crystal Growth.
Participation is free.
26 Contact angle and surface energies at the calcite/solution 10.4 interface
Emanuele Costaa, Dino Aquilanoa
a
Dipartimento di Scienze della Terra – Università di Torino, Italy
[1] D. Aquilano* and L. Pastero: Anomalous mixed crystals: a peculiar case of adsorption/absorption, Cryst. Res. Technol., 1–21 (2013) /DOI
10.1002/crat.201200708 ; [2] M. Bruno, F. R. Massaro, L. Pastero, E. Costa, M. Rubbo, M. Prencipe, D.Aquilano: New estimates of the free energy
of calcite/water interfaces for evaluating the equilibrium shape and nucleation mechanisms. Crystal Growth & Design, 13, (2013) 11701179. doi:10.1021/cg3015817.
Effect of Tb3+ co-doping on BaY2F8:Dy3+ crystals
Daniela Parisia, Giacomo Bolognesib and M. Tonellia,c
a
Istituto Nanoscienze NEST - CNR, Pisa, Italy
b
INRIM Istituto Nazionale di Ricerca Metrologica, Torino, Italy
c
Dipartimento di Fisica, Pisa, Italy
The new generation of optical clocks are based o neutral atoms trapped in an optical lattice. In the recent years one of the most
interesting atom is the Yb, that exploits the 1S0 → 3P0 transition at 578nm [1]. In this frame the development of new solid state laser
sources at 578 nm play a very important role, first because of the lack of direct laser emitter in the yellow region and second to allow
the possibility to miniaturize the optical clock [2]. An attractive candidate as emitter in the yellow region is the trivalent rare earth ion
Disprosium (Dy3+), using the 4F9/2 → 6H13/2 transition.
In this work we present the growth and spectroscopic study of the BaY2F8 (BYF) host, doped with 4at% Dy3+ and the effect of the
codoping with Terbium (Tb3+) on the yellow transition. Two of the most important features of this crystal are its very low phonon
energy (350 cm−1) and its low thermal lensing.
Single crystals of BYF containing 4at% of Dy3+ and different concentrations of Tb3+, (0at% - 1at% and 2.5at%) were grown by
means of the Czochralski method in the Pisa Physics Department Laboratories - National Enterprise for nano Science and
Technology laboratories. The structure of the crystal is monoclinic, space group C2/m with cell parameters a = 6.983 Å, b = 10.519
Å, c = 4.264 Å and β = 99.7°. The growth facility consists of a home made Czochralski furnace with resistive heating and automatic
optical diameter control. The crystal was grown using BaY2F8 powder as raw material for the crystal, and the doping density was
achieved by adding a proper amount of BaDy2F8, TbF3 and BaF2 powders. To avoid OH− contamination, the powders were purified
at AC Materials (FL, USA), obtaining a purity of 99.999%. Special care has been devoted to the quality of the vacuum system, which
has an ultimate pressure limit below 10−5 Pa. Crystal growth was carried out in high-purity argon atmosphere to avoid contamination
in the crystal. During the growth, the rotation rate of the sample was 5 rpm, the pulling rate was 0.5 mm/h, and the temperature of the
melt was around 995 °C. The single crystalline character of the samples was checked using an x-ray Laue technique to identify the
crystallographic axes of the crystal and to cut oriented samples.
Polarized room temperature absorption spectra were acquired using a Cary 500 spectrometer, in the region between 440–490 nm
corresponding to the 6H15/2 → 4F9/2 pump transition of Dy3+. The resolution was 0.1 nm.
Fluorescence measurements have been performed with a standard apparatus exciting the sample with a blue diode laser tuned at 454
nm, according to the absorption spectrum of Dy:BYF. Our attention was focused the yellow region corresponding to the transition
4F9/2 → 6H13/2 (530 – 600 nm) using a photomultiplier detector. The resolution of the spectra was 0.13 nm. We recorded the
27 Poster Session Fundamentals in crystal growth: from bulk to surfaces Determining the specific interface energies in the crystal- solution systems is a fundamental task to improve our knowledge about
nucleation and growth kinetics of crystals. This is notably important in biomineralization phenomena where the interplay of different
polymorphs is markedly affected by the role of adsorption and then of the surface energies.
With the aim at acquiring strategic parameters in the calcite/aqueous solution system, we measured (at room T and P) the contact
angle at the interface between a fresh cleaved (10.4) surface of calcite (CaCO3) and a solution in thermodynamic equilibrium with it.
The simple experimental device we used is made by an optical microscope equipped with a camera to obtain zenithal image of drops
on horizontal surfaces. A portable PC was employed to acquire the images via an USB connection. The statistical reliability of data
was obtained by measuring the contact angle of two series (for a total of 60) droplets of the same volume (20 µl) , while the solution
was coloured with 0.5 ‰ methylene-blue to better find the drop borderline.
From the first series of droplets showing an averaged cap-diameter of 5.700.25 mm, a contact angle 1 = 146.40° has been obtained,
while, from a second series an averaged cap-diameter of 5.940.35 mm gave a contact angle 2 = 131°. By applying the system of
fundamental Young’s (sl = sv + lv cos) and Dupré’s (sl = sv + lv -adh) equations [1] to the (10.4) surface of calcite we obtained
the mean values of both the specific solid-liquid interface energy (sl=409.87 erg cm-2) and the specific solid-liquid adhesion energy
(adh=126.82 erg cm-2). To do that, the reference value we used were sv = 464 [2] and lv (dilute aqueous solutions) = 72.7 erg cm-2,
respectively. The obtained adhesion energy fulfills the constraint adh  2lv = 145.4 erg cm-2, imposed by the coupling of Young’s
and Dupré’s relations and is very promising for attempting further measurements of contact angle on other strategic forms of calcite.
spectra as a function of the Tb3+ concentration in order to study the effect of this codopant on the yellow Dy3+ emission. In Fig 2 we
show the fluorescence comparison of three different Dy-Tb:BYF samples.
The lifetimes at low excitation were measured pumping the samples with a frequency doubled pulsed tunable Ti:Al2O3 (pulse
duration 30 ns) laser, tuned to the 454 nm. We measured the lifetime of 4F9/2 and 6H13/2 manifold of Dy3+ ion, corresponding to
theupper and lower levels involved in the yellow transition. We studied the dependence of the two lifetimes as a fuction of Tb3+
concentration and in Tab.I is summarized the values of lifetime for all the samples.
Poster Session Fundamentals in crystal growth: from bulk to surfaces [1] D. Calonico, F. Levi, et al., IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, 2012, 59, 426.
[2] S. R. Bowman et al, Optics Express 2012, 20, n. 12.
Fig. 1. Boule of BaY2F8: 4% Dy3+
1% Tb3+ as an example of boule
grown
Fig. 2. Fluorescence comparison of the yellow bands
of BaY2F8: 4at% Dy3+ and different concentrations of
Tb3+, from 0at% up to 2.5at%
X-ray diffraction efficiency of bent GaAs (220) mosaic crystals for the LAUE project
Elisa Bonninia,b, Elisa Buffagnia, Claudio Ferraria, Antonio De Sanctisa, Andrea Zappettinia
IMEM-CNR Institute, Parma, Italy
b
Dipartimento di Fisica e Scienze della Terra, Parma University, Parma, Italy
a
In a Laue lens made by single crystals oriented to diffract parallel x-rays at the lens focus, the energy and angular resolution are
limited by the crystal size and by the crystal mosaicity. The use of extended crystals bent according to the lens curvature provides a
28 better focusing, with the resolution given essentially by the crystal mosaicity. With this approach a crystal mosaicity as low as 15-25
arcseconds, well below the mosaicity value of copper crystals, was found suitable for the new design of the Laue lens. The
reflectivity and transmission profiles and the integrated intensity have been measured in flat and bent GaAs and Si crystals prepared
by the method of surface damaging by using sandpaper of different grain size. The surface grinding induces a local lattice strain
which produces a self standing bent crystal. Bent crystals with radius of curvature lower than a critical value given by the extinction
length behave as perfect mosaic crystals or strongly bent perfect crystals, maximizing the diffraction efficiency at high x-ray
energies. It is found that the surface grinding does not affect the crystal diffraction efficiency, the damage thickness being limited to a
few tens microns near the crystal surface.
3D heteroepitaxy on patterned Si substrates: a new monolithic integration strategy
We have recently shown that crystal defects and internal stresses commonly hampering Ge heteroepitaxy on Si can be greatly
reduced by promoting the nucleation of micro-crystals at the top of Si pillars deeply patterned on the substrate [1]. Ge-on-Si epitaxy
by low-energy plasma-enhanced CVD (LEPECVD), allows for controlling the microcrystal faceting, in turn affecting the evolution
of threading dislocations and providing complete expulsion of threading arms to the microcrystal sidewalls [2]. In addition, the
microcrystals are self-assembled in dense arrays, with a spacing ranging from tens to one hundred nanometers. The growth
mechanism of the micro-crystals is an intriguing “nano” effect, which has been interpreted in terms of independent facet growth.
This effect is not a unique feature of Ge deposition by LEPECVD, but a more general growth mode, which can be extended to other
materials systems and deposition techniques. GaAs microcrystals deposited by MBE on patterned Si substrates show as well the
complete tessellation of the surface by closely separated microcrystals. The complete elimination of thermal strain and reduction of
threading dislocations is confirmed by the high photoluminescence yield.
[1] C. V Falub et al. Science 2012, 335, 1330–4 ; [2] A. Marzegalli et al., Advanced materials 2013, 25, 4408
Impact of heavy doping with donors on CZ silicon properties
Maria Porrinia, Januscia Duchinia, Alessia Bazzalib
a
MEMC SpA, Merano, Italy
b
MEMC SpA, Novara, Italy
This work reports recent results on the impact of a high concentration of donor atoms on the properties of large diameter
Czochralski-grown silicon crystals, which are largely used as a starting material for the fabrication of electronic discrete devices. In
particular, the impact on the type and concentration of point defects – vacancies and self interstitials – and on the formation of related
microdefects will be characterized by several experimental techniques (copper decoration and preferential etching, Atomic Force
Microscope, surface laser inspection) and discussed in the light of a recently published mechanism [1].
[1] V.V.Voronkov, R. Falster, M. Porrini and J. Duchini, Phys. Status Solidi A 209 1898-1901 (2012)
Epitaxial germanium deposited by MOVPE on InGaAs quantum dot stressors grown by MBE
Matteo Bosia, Giovanni Attolinia, Paola Frigeri a, Lucia Nasi a, Francesca Rossi a, Luca Seravalli a, Giovanna Trevisia
a
The integration of light emitting sources on Si has been the long standing challenge for the ICT community. Tensile strained Ge is
considered as an enabling material for this goal because it shows unique indirect to direct bandgap transition and very high carrier
mobilities (> 10.000 cm2/Vs). Despite these promising attributes, there is still unmet need in the development of effective growth
techniques for Ge with desirable tensile stress as well as in-depth understanding of the unique properties of these strained Ge layers.
Taking advantage of the tensile strain (TS) field induced by self-assembled QDs in the surrounding matrix, we aim to realize a novel
system in which local tensile strain is applied to a Ge overlayer epitaxially grown on an InGaAs/GaAs QD underlayer. This novel
approach will allow a localized TS modulation of the Ge layer by maintaining excellent Ge crystalline properties.
29 Poster Session Fundamentals in crystal growth: from bulk to surfaces Stefano Sanguinettia, R. Bergamaschinia, S. Biettia, F. Isab, G. Isellab, A. Marzegallia, C. Frigeric, F. Montalentia, F.
Pezzolia, A. Scaccabarozzia, C. V. Falubd, H. von Käneld and L. Miglioa
a
L-NESS and Dip. di Scienza dei Materiali, Università di Milano Bicocca, Milano, Italy
b
L-NESS and Dipartimento di Fisica, Politecnico di Milano, Como, Italy
c
Laboratory for Solid State Physics, ETH Zurich, CH-8093 Zurich,Switzerland
d
Poster Session Fundamentals in crystal growth: from bulk to surfaces To achieve this goal we combined different growth techniques (Metal Organic Vapor Phase Epitaxy – MOVPE – and Molecular
Beam Epitaxy - MBE) and we started to investigate the basis of Ge epiaxial layers deposited by MOVPE on the top of a layer of
InGaAs QDs realized by MBE on GaAs.
MBE-grown epitaxial structures contained one layer of buried and one layer of surface In0.4Ga0.6As/GaAs QDs deposited at 480 °C
on GaAs (100) substrates. Ge growth was performed by MOVPE at two different temperatures (550 °C and 600 °C) using isobutyl
germane as precursor and H2 as carrier gas, at pressure of 60 mbar. The susceptor temperature was raised to the chosen T and the Ge
precursor was immediately delivered to the reactor chamber without any pretreatment. Growth time was fixed at 2 minutes for both
growths. These structures permitted to analyze the effects of Ge regrowth (such as the annealing at high temperature) on both the
buried and surface QDs.
The structures were characterized by Photoluminescence (PL) and Atomic Force Microscopy (AFM) before and after Ge epitaxy.
Transmission Electron Microscopy (TEM) was used to investigate the structure and gain informations about the epitaxial relationship
between the Ge overlayer and the QD stressors.
AFM characterization reveals significant differences in morphological features between the structures with Ge deposited at 550 ° and
600 °C.
Cross sectional TEM analysis show that the Ge overlayer is epitaxially grown on the InGaAs/GaAs QD underlayer, with the same
orientation. No structural defects are observed in the whole structures. The Ge overlayer is about 30 nm for sample deposited at 600
°C, while the growth is hindered for Ge deposited at 550 °C, where only a partial coverage of the QDs is observed.
The buried QDs appear smaller in size in the structure with Ge deposited at 600°C, suggesting that intermixing and In desorption
may have occurred.
PL spectra taken at 10 K show that upon Ge deposition the PL emission from surface QDs is completely quenched. This could be
interpreted as due to the band alignment between InGaAs and Ge that hampers the confinement of carriers in the InGaAs QDs as Ge
has a lower band gap than InGaAs. On the other hand, the emission of buried QDs is preserved, although a slight blue-shift is
noticeable for Ge deposited at 600 °C, that could hint to enhanced Ga-In intermixing within the InGaAs QDs that may lead to a lower
effective In composition into the QD.
Nanoindentation studies of gallium arsenide grown on germanium
Joice Sophia Ponraja,b, Arivuoli Dakshinamoorthyb, Giovanni Attolinia, Matteo Bosia
b
Crystal Growth Centre, Anna University, Chennai, Italy
a
Epitaxial growth of GaAs/Ge is gaining attention because of their light weight, large area space solar cells and high efficiency which
find application in wireless space communication systems [1]. Ge as substrate material is mainly used for solar cells in space
applications and it can also be used as a separate p-n junction in multi junction solar cells, it is lattice matched to GaAs i.e., (aGeaGaAs)/aGe ~0.07%, is less brittle than GaAs and both have similar thermal expansion coefficients [2]. The needs of optoelectronic
industry have driven the study of plasticity of III-V semiconductor heterostructures as the plastic relaxation seriously affects the
device performance.
GaAs/Ge thin films were deposited by metal organic chemical vapor phase epitaxy technique using AsH3 diluted with 10% H2 and
trimethylgallium precursors with III/V ratio of 150 and at a pressure of 60 mbar for 30 minutes. The growth temperatures employed
were 600, 650 and 675°C. Structural properties were studied by HRXRD technique. The deposited epilayers were characterized by
SPM coupled Hysitron TI950 Triboindenter to study the mechanical properties. The mechanical deformation behaviour has been
investigated by nanoindentation technique using Berkovich and Vickers indenters to study the properties such as hardness and elastic
modulus. To avoid the substrate effect, a commonly used rule of thumb is to limit the indentation depth to 10-25% of the film
thickness [3]. Hence, in our case the maximum penetration depth is limited to 50 nm.
From the HRXRD studies, the broad peak of GaAs is attributed to the comparatively less thickness of GaAs epilayers than the Ge
substrate. The peak broadening can be due to the variation in the composition of Ga and As in the epilayers grown. The loadingunloading (P-h) curves of nanoindentation show pop-in during loading and elbow behavior during unloading and it is due to the onset
of plastic deformation. The pop-in event occurs in the loading curve of Vickers indenter at a penetration depth of ~20 nm with the
critical load of ~90 μN. It has been identified that the processes responsible for this pop-in were associated with the dislocation
nucleations [4]. The indentation study reveals that the elastic-plastic response occurred progressively at lower stress levels. The
material underneath the indenter transforms into a new phase if certain stress conditions are met, causes change in P-h curves.
[1] Khvostikov V.P., Khvostikova O.A., et al., Semiconductors 2004, 38, 950 ; [2] Bosi M. and Pelosi C., Progress in Photovoltaics:Research and
Applications 2007, 15, 51 ; [3] Oliver, W.C. and Pharr, G.M., Journal of Materials Research 1992, 7, 1564 ; [4] Jian, S.R., Fang, T.H., et al., Applied
Surface Science 2006, 253, 833.
Crystal bending by surface damaging in crystals for a Laue lens
Elisa Buffagnia, Elisa Bonninia,b, Claudio Ferraria, Andrea Zappettinia, Giuseppe M. Guadalupic
IMEM-CNR Institute, Parma, Italy
b
Dipartimento di Fisica e Scienze della Terra, Parma University, Parma, Italy
a
30 c
Venezia Tecnologie s.p.a., Venezia, Italy
0.003
GaAs (001) oriented
0.002
peak shift (rad)
compressive strain
0.001
0.000
-0.001
not treated
0°: R=7.7 m
90°: R=24.2 m
45°: R=11.7 m
-0.002
-0.003
curvature
-20
-10
0
10
20
position on the sample (mm)
Fig. 1. The treatment introduces defects in a superficial layer of few
tens micrometers in thickness undergoing a highly compressive
strain, obtaining a convex curvature of the treated surface.
Fig. 2. Angular shift of the Bragg angle as a function of the measurement
positions (E=8 keV) along different diameters of a surface treated (001)
GaAs wafer. 0° and 90° correspond to the <110> crystallographic
directions.
[1] Virgilli E., Frontera F., et al., Proc. of SPIE (2013) in press ; [2] C. Malgrange, Cryst. Res. Technol. (2002) 37(7), 654 ; [3] R. K. Smither, K. Abu
Saleem, et al., Exp. Astron. (2005) 20, 201.
Transient Current Spectroscopy and internal electric field
Massimiliano Zanichellia,b, Andrea Santia, Giovanni Piacentinia, Maura Pavesia.
a
Department of Physics- University of Parma, Italy.
b
IMEM-CNR, Parma, Italy.
CdTe and CZT, despite the great efforts spent in the past years in the growth techniques, are still materials difficult to growth with
transport properties far from those of the traditional semiconductors for radiation detection. In particular, the difficulties in the
growth cause a large number of defects that affect the shape of the internal electric field when a bias is applied. In the latest years an
increasing number of experimental evidences are showing how the electric field within the CdTe or CZT detectors is far to be
constant. Recent contributions, in particular have shown as, in wide part, the internal electric field seem to be linearly decreasing.
The authors examine as this profile of electric field affects the pulse response and the charge collection efficiency of planar detectors,
taking into the account also the diffusion processes. Moreover the authors suggest a new method to reconstruct the shape of the
internal electric field starting from the detector pulse response and, in the same time, to obtain material transport parameters as
mobility and life-time.
31 Poster Session Fundamentals in crystal growth: from bulk to surfaces The focusing of hard x- and gamma-rays with energies in the 70-600 keV range is a crucial point for space astrophysics, and the use
of a Laue lens made of single crystals in the Laue diffraction configuration has been proposed to efficiently collect rays of these
energies [1]. Perfect crystals cannot be considered as optical elements of the Laue lens due to their very narrow angular range of
diffraction at high energies. Mosaic crystals, thanks to their mosaicity degree, can get round this problem; on the other hand, their
diffraction efficiency cannot exceed the limit of 50%. Curved crystals can be suited to overcame both these limits: in bent crystals the
diffraction range is given by the total curvature of the crystal lattice planes and the diffraction efficiency can reach values close to
100% [2]. Curved crystals based on composition gradient SiGe alloy, for example, can be used as optical elements showing excellent
performances [3]. Unfortunately, a large production of such crystals seems prevented by the difficulty in the crystal growth and the
yield rate.
In this work we propose a different strategy to obtain curved crystals: to achieve the bending by introducing a surface strain in plane
crystals by means of a controlled damaging by sandpapers of different grain sizes. The treatment introduces defects in a superficial
layer of few tens micrometers in thickness undergoing a highly compressive strain, obtaining a convex curvature of the treated
surface (see Fig. 1). Several (001) oriented silicon (Si) and gallium arsenide (GaAs) wafer crystals and (111) oriented germanium
(Ge) ones have been afterwards treated. The local and mean curvature radii of each sample have been determined by means of high
resolution x-ray diffraction measurements in Bragg condition at low energy (8 keV). Curvature radii between 3 and 70 m were easily
obtained in wafers of different thicknesses. Furthermore, Si and Ge samples showed nearly spherical curvatures, whereas GaAs
treated samples evidenced an elliptical curvature with major axes corresponding to the <110> crystallographic directions parallel to
the surface (see Fig. 2). Preliminary results of measurements performed in Laue geometry on GaAs samples at the beamline ID15A
of ESRF, Grenoble, with gamma-ray energy of 120 keV are also reported. Rocking curves with square shape as expected from theory
in perfect bent crystals and a high diffraction efficiency are obtained in surface treated curved crystals. On the basis of these results,
GaAs 30x10x2 mm3 crystals with a curvature radius of 40 m were prepared for a prototype of Laue lens.
Obtaining High quality 3C-SiC thin films on silicon substrate optimizing the SiC buffer layer
Poster Session Fundamentals in crystal growth: from bulk to surfaces Matteo Bosia, Giovanni Attolinia, Marco Negria, Cesare Frigeria, Elisa Buffagnia, Claudio Ferraria, Tiziano Rimoldib,
Luigi Cristofolinib, Lucrezia Aversac, Roberta Tattic, Roberto Verucchic
a
IMEM-CNR, Parco Area delle Scienze 37/A, 43124 Parma, Italy
b
Dipartimento di Fisica e Scienze della Terra, Università degli Studi di Parma, Italy
c
IMEM-CNR, Via alla Cascata 56/C, 38123 Trento, Italy
Some of the excellent SiC properties such as a superior radiation and chemical tolerance, high hardness and Young’s modulus, high
thermal conductivity (higher than copper) and a high critical electric field (more than 2 MV·cm−1), together with its biocompatibility
pushed a dramatic development in SiC technology over the last few years.
3C-SiC can be grown on Si and this allow to exploit the synergy with the well-developed silicon technology, but the relatively high
lattice mismatch (20%) and thermal mismatch (8%) can still be an issue to obtain thin films with high crystalline quality.
This work is focused on the optimization of a 3C-SiC buffer layer between the Si (100) substrate and the epitaxially grown SiC.
The first growth step is a carbonization of the silicon substrate with propane (C3H8) at high temperature (1125° C) to convert Si
surface into SiC, then a 100-150 nm thick SiC buffer layer is deposited onto it. This stage was fundamental to obtain a high quality
epitaxial SiC layer.
The buffer layer is grown by varying silane (SiH4) and propane (C3H8) concentration while the temperature is increased up to the
growth temperature (1380° C).
To find the best conditions, different heating rates and precursor flows during buffer layer growth were tested. The process was
interrupted to check the crystalline quality and the presence of voids at the SiC/Si interface at different stages, and analysed by
Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM), Raman, Transmission Electron Microscopy (TEM), XRay- Photoelectron Spectroscopy (XPS) and X-Ray Diffraction.
In particular it was found the role of heating ramp rate as a key factor influencing polycrystalline content and interfacial voids
density.
At the end high quality 3C-SiC thin films were grown using SiH4 and C3H8 at 1380° C and 200 mbar, the good crystalline quality
was assessed by means of XRD measurements (FWHM of about 790 arcsec) and TEM. Raman measurements revealed a residual
tensile strain of about 0.03% compared to the bulk.
The surface was characterized with AFM and the roughness found was remarkably low (<1 nm on 1x1 µm2 scale).
Electroless gold contact deposition on CdZnTe detectors by scanning pipette technique
Nicola Zambellia,b, Laura Marchinia, Giacomo Benassia, Davide Calestania, M. Pavesib, Andrea Zappettinia
a
b
Dept. Physics, Parma University, Italy
CdZnTe is one of the most exploited materials for the realization of room temperature X- and gamma- ray detectors. However the
final cost of the devices remains a limiting factor for large-scale applications.
One of the problems is connected with the realization of contacts. Due to the difficulty to obtain large single wafers, usually
photolithography is carried out on a single device, strongly increasing the cost of detector fabrication. On the other side because of
the important role played by the metal-CZT interface on the functioning of the final device, a special attention should be paid to the
technology employed in the realization of metal contacts.
Recently, a novel, reproducible and low-cost method for gold deposition on CZT surface has been developed combining two
different technologies: scanning pipette technique and electroless deposition [1]. With this technique it is possible to avoid the
photolithography process and still obtain complex contact patterns with a good spatial resolution and high reproducibility.
In this work, it is shown that contacts with dimensions down to a few tenths of microns can be obtained. The contacts show good
mechanical stability and optimal current-voltage characteristics. High-resolution CZT detectors have also been demonstrated by the
use of this technology.
Moreover, the technology is shown to be easily adapted to the deposition of other metals than gold, for example platinum or
palladium, by simply changing the deposited solution.
[1] N. Zambelli, L. Marchini, G. Benassi, D. Calestani, A. Zappettini, RTSD 2011, Valencia, Poster S 312.
Heteroepitaxy of Ga2-2xIn2xO3 layers by MOVPE with different oxygen sources
Michele Baldini, Daniela Gogova, Klaus Irmscher, Albert Kwasniewski, Martin Schmidbauer, Günter Wagner and
Roberto Fornari
Leibniz Institute for Crystal Growth, Berlin, Germany
32 E-mail: [email protected]
[1] Granqvist C.G., HultakerA., Thin Solid Films 2002, 411, 1 ; [2] Cebulla R., Wendt R., et al., J. Appl. Phys. 1998, 83, 1087 ; [3] Rakhshani A.E.,
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1991, 4, 437-441 ; [10] Rebien M., Henrion W., et al., Appl. Phys. Lett. 2002, 81, 250 ; [11] Walsh A., Da Silva J.L.F., Phys. Rev. Lett. 2008, 100,
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L., Ma J., et al., J. Solid State Chem. 2011, 184, 1946 ; [17] Kong L., Ma J., et al., J. Alloys Compd. 2010, 499, 75.
Structural and electronic properties of VZn in ZnO nanostructures: a combined experimental and theoretical
study
Alessandra Catellani1,2, A. Calzolari2, F. Fabbri1, M. Villani1, D. Calestani1, A. Zappettini1, G. Salviati1
1 CNR-IMEM, Parma, IT
2 CNR-NANO Istituto Nanoscienze, Centro S3, Modena IT
Zinc oxide (ZnO) plays a key role in today material science because it combines the possibility of being synthesized in a wide
assortment of different nanostructures (nanowires, nanorods, nanotetrapods, nanocombs, etc.[1–3] with a large number of application
fields (optoelectronic, photovoltaic, gas- and biosensing, photocatalysis)[4]. Yet several issues related to intrinsic n-type character,
and defective stoichiometry reduce the actual impact for the realization of stable devices. Thus, a controlled improvement of the
material cannot leave out a microscopic understanding of the surface states and of the deep levels of the ZnO. This is particularly true
33 Poster Session Nanoepitaxy Transparent Oxide Semiconductors (TSOs) are an emerging class of materials, which combine the electrical properties typical of
semiconductors with a high transparency, up to the UV region of electromagnetic spectrum. These compounds take advantage of the
concepts developed by Transparent Conductive Oxide (TCOs), such as indium tin oxide (ITO) [1], aluminum-doped zinc oxide
(ZnO:Al) [2] or fluorine doped tin oxide (FTO) [3], which are already employed as transparent contacts in a wide range of devices:
light-emitting diodes, solar cells, LCD displays, and smart windows [4-6]. TCOs have usually amorphous or polycrystalline structure
and present only n-type conductivity. To provide sufficiently low resistivity (<10-4 Ωcm), the carrier concentration should be at least
on the order of 1020 cm−3, limiting the mobility at relatively low values (~80 cm2/Vs) by ionized impurity scattering [7]. In the last
years the attention have focused on developing metal-oxides not only as mere conductors, but as proper semiconductors (TSOs), with
higher crystallographic properties and an intermediate carrier concentration level, in the range of 1017-1019 cm-3, which allows to
modulate the extension of the depletion layer in pn junctions and Schottky barriers. By growing single crystal films it should be
possible to obtain enhanced carrier mobility values, as required for the realization of transparent active junctions for microelectronic
and optoelectronic applications [8].
Monoclinic β-Ga2O3 is one of the most interesting example in this class of materials, thanks to its large direct band gap (4.9 eV) that
turns into high transparency till the medium-UV spectrum range, and high break-down field (8 MV/cm), which leads to minimize
conduction losses in high-power device applications [9, 10]. In order to modulate its energy gap, β-Ga2O3 can be alloyed with In2O3,
characterized by an optical bandgap of 3.75 eV [11, 12]. This open the field to a broad spectrum of applications such as graded
heterostructures for optoelectronic devices, photodetectors sensitive to tunable wavelengths, optical filters with tunable transmission
range, and so on. However, Ga2-2xIn2xO3 alloy cannot be grown in the whole 0<x<1 interval, since Ga2O3 and In2O3 have different
crystallographic structures, belonging to monoclinic (space group C2/m) and cubic (space group la-3) systems, respectively. This
means that phase separation will occur, beyond a x limit value. In literature, it is known that through solid state reactions in powder
synthesis, it is possible to introduce up to about 40% of In2O3 in Ga2O3 maintaining a monoclinic symmetry, while, in the opposite
case, the solubility limit of Ga2O3 in In2O3 is only about 10% [13, 14]. On the other hand, for thin film growth, there are some reports
but still no clear data about the solubility limit of these two compound [15-17].
In this work we present the growth of Ga2-2xIn2xO3 layers by metal organic vapour phase epitaxy (MOVPE) on c-plane oriented
sapphire in a vertical low-pressure reactor. The precursors employed for Ga and In were trimethylgallium (TMGa) and
trimethylindium (TMIn), respectively, while as an oxygenation source pure O2 and H2O were alternatively used. Pure Ar worked as
carrier gas. The reactor base pressure was maintained between 5 and 100 mbar, while the optimal growth temperature was explored
in the 750-850 °C interval. Typical growth rates were in the range 2-8 nm/min. The solubility limit of In2O3 in the Ga2O3 matrix was
studied and discussed through the analysis of XRD and optical absorption spectra at different growth conditions. The layers were
carefully characterized from structural, optical and electrical point of view and the peculiar effects due to the two alternative oxygen
sources were investigated, especially regarding the incorporation of In into Ga2O3.
By using pure O2 during the growths, the XRD pattern of the layers showed that, in addition to β-Ga2O3, In2O3 was always obtained,
whatever the amount of TMIn injected into the reactor. The second phase formation was confirmed by a double step feature placed at
the absorption edge of the two materials in optical absorption spectra. On the other hand, with H2O as oxygenation source, no In2O3
phase was observed and, at the same time, In incorporation was confirmed by energy-dispersive X-ray spectroscopy. Through XRD
and optical absorption measurements, the growth of the Ga2-2xIn2xO3 mixed phase was confirmed: in the first case, the Ga2O3-related
peaks shifted at lower 2θ angles (larger lattice parameter) as expected from the substitution of Ga3+ ions by bigger In3+ ones, while in
the second one, the absorption edge moved correctly from the Ga2O3 bandgap value towards that of In2O3. The reactor pressure
turned out to have a fundamental role in the In incorporation process.
for low-dimensional nanostructures, which have high surface-to-bulk ratio, and the effects of surface recombination are not limited to
band-to-band recombination quenching, but may actually provide detrimental electron traps.
In order to gain insight on the microscopic origin of the green emission in ZnO, we propose a combined cathodoluminescence (CL)
and ab initio DFT study of ZnO one dimensional nanostructures. Here, we address the defects formation probability of specific
crystallographic surfaces comparing experimental results and theoretical simulations. Our results clearly allow assigning in a not
ambiguous way a determinant role of Zn vacancies on the green emission properties of ZnO nanostructures, whose control is
expected to reduce the undesired charge recombination in optical and electronic devices[5].
[1] 1 Z. L. Wang, Mater. Today, 7, 26 (2004) ; [2] Z. L. Wang, J. Phys.: Condens. Matter, 16, 829 (2004) ; [3] M. Z. Zha, D. Calestani, A. Zappettini,
R. Mosca, M. Mazzera, L. Lazzarini and L. Zanotti, Nanotechnology, 19, 325603 (2008) ; [4] L. Schmidt-Mende and J. L. MacManus-Driscoll,
Mater. Today, 10, 40 (2007) ; [5] F. Fabbri, M.Villani, A.Catellani, A.Calzolari, B.Dierre, D.Calestani, G. Calestani, A.Zappettini , T.Sekiguchi,
G.Salviati, in preparation.
Poster Session Nanoepitaxy Self assisted growth of GaAs nanowires stopped and resumed
Silvia Rubinia, Giacomo Priantea, S. Ambrosinia,b,c, V.G. Dubrovskiib, A. Franciosia,d
a
IOM-CNR, Trieste Italy
b
St. Petersburg Academic University, Russia
c
Durham University, UK
d
Sincrotrone Trieste S.C.p.A, Trieste, Italy
Semiconductor nanowires (NWs) are attracting great interest for their potentials as building blocks of novel electronic and
optoelectronic nano-devices as well as for their peculiar growth mechanisms. They are commonly obtained exploiting the presence of
a metal nanoparticle (NP), acting as a collector for the incoming material and promoting the anisotropic growth. Although gold is by
far the most employed metal, gold-free “self-assisted” growth methods have been developed for III-As materials, in which gold is
replaced by the group III metal [1,2]. In contrast with the case of Au, the Ga nanoparticle at the NW tip can be consumed by
changing the As/Ga flux ratio at the growth temperature. This procedure has already been used to promote the growth of a shell
around the nanowires, after a suitable change of the growth conditions [3].
In this contribution we demonstrate that Ga-assisted GaAs NW growth can be resumed after the complete extinction of the Ga
nanoparticle. The new growth (regrowth) of the NW starts when a new Ga nanoparticle condensates on the flat (111) surface at the
NW tip. We show that this can be achieved either by resuming GaAs growth in Ga-rich condition, or by depositing Ga alone.
Examples of regrown wires are shown in Fig. 1.
During the regrowth process, the NW grows in length at the same rate observed before the extinction of the Ga nanoparticle, while
the diameter increases at a faster rate, so that the regrown NW recovers quickly the original diameter. The nanowire length and
diameter dependence on growth duration for both growth and regrowth processes are well reproduced by an analytic model, that
highlights the role of Ga atoms impinging on the top NW facets on the rapid recovery of the NW diameter during regrowth.
The presented mechanism opens the way to the growth of engineered NW structures, where axial and lateral growth could be
controlled independently.
Fig. 1 Collage of SEM images picturing the topmost region of GaAs nanowires observed just
after the consumption of the Ga nanoparticle (left) and following subsequent exposure to Ga
and As beams for 30 s, 60 s, 150 s and 300 s, from left to right, respectively.
[1] Fontcuberta i Morral, A.; Colombo, C.; Abstreiter, G.; Arbiol, J.; Morante, J. R. Applied Physics Letters 2008, 92, 063112 ; [2] Jabeen, F.; Grillo,
V.; Rubini, S.; Martelli, F. Nanotechnology 2008, 19, 275711 ; [3] Colombo, C.; Heiβ, M.; Grätzel, M.; Fontcuberta i Morral, A. Applied Physics
Letters 2009, 94, 173108.
Epitaxial growth of magnetic thin films and heterostructures for data storage and energy applications
Francesca Casolia, Simone Fabbricia,b, Pierpaolo Lupoa, Valentina Chiesia, Paolo Ranzieria, Lucia Nasia, Marco
Campaninia, Franca Albertinia
a
34 b
MIST E-R, Bologna, Italy
[1] Casoli F., Albertini F., et al., Acta Materialia 2010, 58, 3594 ; [2] Ranzieri P., Fabbrici S., et al., Acta Materialia 2013, 61, 263.
Growth and characterization of germanium nanowires
Giovanni Attolini, Francesca Rossi, Matteo Bosi
One dimensional materials have led to an active area of research in recent years. Nanowires (NWs) exhibits unique electronic, optical
and mechanical properties as results of their low-dimensionality.
Germanium has low band gap and high carrier mobilities and it is an appealing candidate for the next generation high transport
channel devices. Ge NWs exhibit also a great potential in the field of nanoelectronic devices.
Many methods have been developed to growth Ge NWs such as: laser ablation, vapor transport, low-temperature CVD (Chemical
Vapour Deposition).
In this work we report on the synthesis and characterization of single crystalline Ge nanowires on silicon substrate via thermal
evaporation of germanium powder. Gold was used as catalyst.
The germanium source and substrate were placed in a open quartz tube insert into a furnace, evacuated and flushed with nitrogen or
argon.
35 Poster Session Nanoepitaxy The more and more challenging requests of the data storage industry and new findings in the field of spintronics have driven the
interest of magnetism research community towards the design and growth of thin films with high structural quality. Since the
Nineties several research groups have demonstrated the possibility to employ a sputtering apparatus to epitaxially grow thin films and
heterostructures of metallic alloys with different functional magnetic properties, e.g. huge magnetocrystalline anisotropy,
ferromagnetic shape-memory, giant magnetoresistance. This demonstration has paved the way to the development of new devices,
leading in some cases to important technological breakthroughs, as in the case of hard disk’s reading heads based on the tunnel
magnetoresistance effect.
We have used a RF sputtering apparatus to grow thin films and heterostructures of different magnetic metallic materials. The system
characteristics have been optimized for the epitaxial growth: base pressure of 2×10-8 mbar, sputtering rates in the range 0.13-1 Å/s,
growth temperature up to 450 °C. Using single-crystalline substrates with different lattice parameters, i.e., MgO, SrTiO3, and LSAT,
we have obtained epitaxial thin layers (thickness from 3.5 to 200 nm) of L10-FePt, Ni-Mn-Ga, and Mn-Ga; the films show a variety
of different morphologies, depending on substrate, film thickness, growth temperature and annealing temperature. We have exploited
the alternate layer deposition from three different targets to obtain specific and variable compositions of the metallic alloys; this
technique has shown a high reliability in spanning a wide compositional range and, in the case of the FePt alloy, allowed us to reduce
the growth temperature for chemical ordering. In this successful case we were able to obtain the L10 ordered phase at temperatures as
low as 400 °C.
We have studied the correlation between nanoscale structure and magnetic properties, taking advantage of high resolution X-Ray
Diffraction, Transmission Electron Microscopy, Atomic and Magnetic Force Microscopy, and high sensitivity magnetometry
(Alternating Gradient Force, SQUID and Anomalous Hall Effect).
We have proposed and realized two different exchange-coupled composite (ECC) systems, i.e., epitaxial heterostructures, where a
magnetically soft phase (Fe and Fe3Pt in the two cases) is grown onto a magnetically hard phase (L10-FePt, 10 nm thickness). ECC
media have been proposed to go beyond the magnetic recording “trilemma” by exploiting the hard/soft exchange-coupling to reduce
the switching field without reducing the thermal stability, thus allowing a further increase of information density in next generation
hard disks. We have fully investigated the reversal process in the different magnetic regimes occurring at variable soft layer thickness
(2 - 10 nm), focusing onto the effect of interface morphology in Fe/FePt bilayers and exploiting different substrates to obtain
Fe3Pt/FePt composite islands with variable morphology, size, and inter-island separation [1].
We have grown and studied Ni-Mn-Ga thin films with thickness in the range 10 – 200 nm on MgO (with and without a Cr buffer
layer); arrays of nanodisks were also obtained by polystyrene nanospheres lithography based on the self-assembling of nanospheres
(starting diameter 800, 220 nm) on Ni-Mn-Ga continuous thin films (thickness: 75, 100 nm). The ferromagnetic shape memory alloy
Ni-Mn-Ga is a multi-functional material exploitable in micro/nano-actuators, energy harvester and micror/nano-refrigerators, thanks
to the peculiar coexistence of a martensitic transformation and magnetically ordered states. We have performed a thorough magnetic
and structural characterisation in order to verify the effect of thickness reduction and lateral confinement on martensitic
transformation temperature, on the martensitic microstructure and magnetic domain structure. Thickness, for instance, is a key
parameter for establishing the room temperature phase between austenite and martensite, and for the selection of martensitic variants:
when the film thickness exceeds the critical value of 40 nm, the martensitic phase is present with a twin-variant structure and the
unique axis of the pseudo-orthorhombic 7M modulated structure perpendicular to the plane. At 100 nm thickness and above,
martensitic variants with the unique axis parallel to the film plane have also been found [2]. Cr buffer layer was found to strongly
affect the preferential unique-axis orientation.
Very recently, we have been able to epitaxially grow thin films of the metastable tetragonal phase of Mn-Ga alloy (close to Mn3Ga
composition). This films possess exceptional magnetic and electronic properties, i.e., a unique combination of low magnetization,
high uniaxial anisotropy, high Curie temperature and high spin polarization, which make them very promising as ferromagnetic
electrodes in Spin-Transfer-Torque Magnetic RAMs.
The temperature was increased to reach 850°C and 600°C for source and substrate respectively and kept for 30 min.
The morphology and crystal habit of the grown nanowires were further investigated by Field Emission Gun Scanning Electron
Microscopy (FEG-SEM) while the Transmission Electron Microscopy (TEM) (Jeol – JEM 2200 FS) for High – Resolution (HRTEM) studies and High Angle Dark Field imaging in Scanning mode (HAADF-STEM) and the SAD patterns proved useful for
detailing the nanowires structure.
SEM image for the as-grown Ge nanowires shows a dense network of NWs; they appear very thin, having a uniform diameter of 3040 nm and tens of micrometers long.
Structural characterization performed by TEM shows uniform diameter without defect (such as dislocations and stacking faults),
cubic structure with a preferential growth orientation in the [111] direction.
A thin layer of amorphous germanium oxide with a thickness of 10 nanometers is all around the Ge NWs.
Poster Session Nanoepitaxy Uniaxially-oriented epitaxial nanowires of H2TPP
Marcello Campioneb, Gian Carlo Capitanib, Luisa Raimondoa, Massimo Moreta, Adele Sassellaa
b
a
The growth of porphyrinic nanostructures of well-defined shapes and sizes has received much interest due to their attractive
photophysical, photochemical, and electronic properties. The self-assembly of porphyrin nanostructures in organic solvents and in the
solid state is well known, but always relies on the establishment of relatively strong interactions such as hydrogen bonding, metal
coordination, and ionic bonding. When only π−π interactions are active, the formation of unwanted irregular aggregates usually
occurs. Here, we develop an epitaxial strategy for growing uniaxially-oriented and crystalline nanowires of free-base tetraphenyl
porphyrin (H2TPP). The process is based on the growth of the organic adsorbate on a water-soluble single crystalline substrate,
properly designed for inducing the anisotropic diffusion of ad-molecules. The so-obtained nanowires are characterized by optical
absorption spectroscopy, scanning probe microscopy and transmission electron microscopy, giving a thorough landscape of
morphological and structural properties of the assembly. Thanks to the solubility of the substrate, wet-transfer techniques can be
applied and the nanowires placed on any other solid substrate maintaining their uniaxial order. Otherwise, they can be dispersed in
other liquids in view of more complex processing of the active nanostructures.
1D transparent conductive oxides for plasmonics: near-infrared activity in In-doped ZnO nanowires
Arrigo Calzolari1, A. Ruini1,2 A. Catellani1
1
CNR-NANO Istituto Nanoscienze, Centro S3, Modena IT
2
Dipartimento di Fisica, Univerità di Modena e Reggio Emilia, Modena, IT
Noble metals such as gold and silver are conventionally used as the primary plasmonic building blocks in the fields of the
telecommunications and energy conversion. Both localized surface plasmons in nanoparticles and surface plasmon polaritons (SPPs)
propagating at metal/semiconductor interfaces are of interest for optoelectronic applications: the formers can be exploited in
photovoltaic systems as amplifier optical antenna that increase the absorption of incident solar light through excitation of particle
plasmon resonances; the latters provide the opportunity of confining light in very small dimensions, thus acting as subwavelength
scattering elements to couple and trap freely radiations and propagating over long spatial range [1].
However, metals are plagued by large losses, especially in the UV–vis and IR spectral ranges, arising in part from interband
electronic transitions and in part from dissipative scattering events. These losses are detrimental to the performance of plasmonic
devices, seriously limiting the feasibility of many plasmonic applications. As an alternative, heavily doped semiconductors can
exhibit a small negative real permittivity (i.e. high conductivity) and very small losses at the infrared and longer wavelengths.
Here we present a first principles investigation of the optical and plasmonic properties of In-doped ZnO nanowires [2-4], which have
been envisaged as plasmonic nanoparticles in solar or fuel cells for energy conversion [5]. By means of first principles simulations
based on density functional theory, we first characterize the optoelectronic properties of In:ZnO nanowires, as a function of the
impurity sites (buried vs on-surface). The presence of metal impurities imparts to nanowires optoelectronic properties typical of
transparent conducting oxides (TCOs) [2-3]. Then we show the presence of plasmon resonances in In:ZnO wires, and their
dependence on doping dosage. These systems present tunable plasmonic activity in the near-IR range and in particular at
wavelengths relevant for telecommunications (1.5 µm) [6].
[1] W.A. Murray and W. L. Barnes, Adv. Mater. 19, 3771 (2007) ; [2] M. Bazzani, A. Neroni, A. Calzolri and A. Catellani, Appl. Phys. Lett. 98,
121907 (2011) ; [3] A. Catellani, A. Ruini, G. Cicero, and A. Calzolari, Phys. St. Sol. (2013), in press ; [4] A. Calzolari, A. Ruini, and A. Catellani,
preprint (2013) ; [5] H.A. Atwater and A. Polman, Nat. Mater. 9, 205 (2010) ; [5] G. Naik et al, PNAS 109, 8834 (2012).
36 Effect of different catalysts on the vapour phase growth of SiC nanowires
Paola Lagonegroa, S.C. Dhanabalana, M. Negria, G. Attolinia, M. Bosia, F. Rossia, M. Campaninia, F. Boschia, A. Bosiob,
D. Menossib, N. Romeob, G. Rosab, P.P. Lupoa, T. Besagnia, G. Salviatia
a
b
Physics department, Università di Parma, Italy
Nanoepitaxial vapor phase growth of vertically aligned ZnO nanowires
Sathish Chander Dhanabalana, Davide Calestania, Marco Villania, Laura Lazzarinia, Francesco Pattinia, John Paul
Garciaa, Stefano Rampinoa and Andrea Zappettinia
a
Zinc oxide is one of very interesting semiconductor material because of its physical and chemical properties. ZnO material has a
direct band gap of 3.37 eV and a large exiton binding energy of 60 meV at room temperature. Also it has a polar crystal structure and
excellent piezoelectric properties. ZnO is easy to obtain in nanostructures with different forms due to its peculiar properties allowing
researchers to design more complex 3D structures for ZnO based power generators and TCOs and with smarter light and more
efficient short range charge collection in excitonic solar cells. Also, ZnO nanowires used for high temperature and radiation resistant
circuits, n-type gas sensors, cantilever production, for the preparation of diluted- and ferro-magnetic materials for semiconductor
spintronics. Solution based growth of vertically aligned ZnO nano-wires (NWs) is generally the most suitable technique for cheap
and large scale production, but it cannot always be matched easily with the deposition processes of other cell components or the
intrinsic doping from solution inclusions may degrade the device performance. In contrast, vapor phase growth is generally less
controllable and more expensive, especially when metal-organic precursors or metal catalysts are used in order to improve the
synthesis reproducibility. In the present work authors have explored an alternative solution free and catalyst-free synthesis process
that combines two different techniques, i.e. a pulsed electron deposition (PED) and sputtered of ZnO:Al (AZO) films on commercial
glass substrates and a self-catalyzed vapor phase growth of vertically aligned ZnO-NWs at relatively low temperature on different
grain size AZO/glass and ITO/glass substrates. ZnO-NWs were grown by the optimized vapor phase technique described in [3]
directly on the ZnO and AZO (2 wt% nominal Al content) films obtained by PED and sputtering and commercial ITO substrates.
Commercial Zn was used as source material in a quasi-closed container and it was placed side-by-side with substrate in a tubular
furnace in the downstream position. The growth temperature was 480 °C and Ar was used as an inert transporting gas. O2 was
introduced for oxidation (1:20 O2: Ar ratio, 50 sccm) only when the maximum temperature was reached and then kept for 5 min only.
As reported, small Zn nanoclusters on the polar surface of a (001)-oriented ZnO/AZO film can generate preferential, energetically
37 Poster Session Nanoepitaxy Nanostructured materials, nanowires (NWs) in particular, spurred a strong research for the design and fabrication of nano-scale
devices. This exciting and up-and-coming research area crosses different fields, from nanoelectronic devices (e.g. nano field-effect
transistors) to nanophotonics.
Cubic silicon carbide (β-SiC or 3C-SiC) is a wide band-gap semiconductor with high hardness, high electron mobility, high thermal
conductivity and high resistance to chemical attacks. These properties make of SiC NWs one of the most attractive candidates for
devices operating in harsh environments such as nano-electromechanical systems and nano-sensors exploiting the SiC NWs as
biocompatible nanoprobes for biological systems.
Further, functionalized 3C-silicon carbide nanowires have the potential to act as highly sensitive detector elements in bio-chemical
field.
In this work we studied the properties of 3C-SiC nanowires prepared on (100) silicon substrate and the effect of three different metal
catalysts (nickel, iron and gold) on the growth was examined.
A 2 nm thick Nickel film was deposited on Si(100) substrate using an e-beam system whereas iron and gold have been deposited as
a thin layer (same thickness) using a sputtering system.
We used the more conventional nickel as reference catalyst, while Fe and Au were tested in order to enhance the biocompatibility, in
the framework to use NWs in biological systems.
Using the metal-silicon phase diagrams as a reference for the different catalyst, the growth process was developed in a home-made
VPE reactor finding the optimal parameters in order to obtain reliable results and a good crystalline quality of the nanowires.
The typical growth experiment started with the so-called dewetting, a thermal treatment performed to obtain a pattern distribution of
metal droplets, which then acts as catalytic particles for the final epi-growth in mixtures of silane (SiH4) and propane (C3H8).
The growth temperatures were 1100°C and 1250°C when Ni and Fe respectively were used. For gold catalyst the temperature was
increased from 600 °C to the growth temperature of 1100°C in presence of propane.
X-ray diffraction (XRD) has been used to identify the nanowires structure over large area. The morphology and crystal habit of the
grown nanowires were further investigated by Scanning Electron Microscopy (SEM) while Transmission Electron Microscopy
(TEM) imaging and SAED patterns were used to determine the nanowires structure at the nanoscale.
From morphological point of view the SiC nanowires appear similar with a dense network distributed on the substrate, but their
diameter was smaller for those grown using Ni respect to those with iron. In samples where the gold has been used, only a few NWs
were obtained with a presence of Si flakes.
XRD and TEM were used also as diagnostic tools to confirm the cubic SiC structure of the wires.
favored and oriented nucleation sites for the growth of homogeneous arrays of aligned NWs. A growth setup that promotes the
formation of such nanoclusters has been defined and 20-50 nm thick and 1-3 μm long aligned ZnO nanowires have been obtained on
the AZO substrate obtained by PED. But, the nanowires growth on the sputtered AZO substrate has been different in size due to large
epitaxial grain size compare to the AZO obtained from PED. 100-200 nm thick and 2-4 μm long aligned ZnO nanowires have been
obtained on the sputtered AZO substrate. AZO resistivity after NWs growth was still higher than 1.0x10−3 cm and transparency still
high. The obtained samples are homogeneous on the growth area (few cm2) and both the film deposition and the NWs growth can be
easily patterned by mechanical masks.
Acknowledgements: This project has been partially supported by” Nanowiring” European FP7-People: ITN project.
[1] Z. L. Wang, et al., Mater.Today, 2006, 7, 26 ; [2] M. Z. Zha, et al , Nanotechnology, 2008, 19, 325603 ; [3] D. Calestani et al , CrystEngComm,
2011, 13, 1707.
Poster Session Material engineering for PhotoVoltaic conversion in the world of 1 $/W silicon panels Target properties and substrate treatment effects on ZnO:Al grown by dc-magnetron sputtering
Ilio Miccolia, R. Spampinatob, P. Pretec, and N. Lovergineb
a
R&D Lab, Alfa Impianti Srl, Galatone, Lecce, Italy
c
Dip. di Ingegneria dell’Innovazione, Univ. del Salento, Lecce, Italy
b
IMM-CNR, Lecce, Italy
Thin films of aluminum-doped ZnO (ZnO:Al) continue to attract considerable interest as transparent conductive oxide (TCO)
coatings for a variety of applications, including II-generation photovoltaics and thin-film transistors. In substitution of the more
traditionally used Indium-Tin-Oxide (ITO), ZnO:Al allows for the use of inexpensive, non-toxic and abundant elements. Several
deposition methods, e.g., sputtering, thermal evaporation, chemical vapour deposition (CVD), sol-gel and spray pyrolysis have been
reported in the literature. Among them, the direct current (DC) magnetron sputtering deposition remains one of the most attractive
technique for the growth of ZnO:Al layers, because it is a relatively simple and industrially scalable process, and it guarantees films
with high uniformity over large areas, dense structure and good crystallinity. It is known that DC-sputtered thin films properties are
influenced by substrate temperature, DC power, and deposition pressure. However, the correlation between target materials and film
properties needs still to be assessed. In particular, the effects of manufacturing methods (e.g. Slip Casting, Hot Pressing -HP- or Hot
Isostatic Pressing -HIP-) and electrical properties of the ZnO-Al2O3 ceramic targets on the properties of deposited films (e.g.
materials resistivity, and optical properties) have been rarely highlighted until now [1-3]. In addition, lacking consideration has been
also deserved to the effect of substrate surface pre-treatments onto morphological, structural and electrical properties of as-deposited
ZnO:Al films. Here, we report on the DC-sputtering deposition of ZnO:Al films onto monocrystalline (002)-oriented Al2O3
(sapphire) and fused silica substrates, using two different high-density sintered ZnO-Al2O3 composite ceramic targets, e.g. produced
by Slip Casting and HP methods. Several wet and dry cleaning treatments were adopted to remove organic and metallic contaminants
from substrate surfaces, ensuring a substrate surface rms roughness well below 1 nm. The surface morphology, and the structural and
optical properties of ZnO:Al layers deposited at high temperature (350°C<T<450°C) were studied by combining atomic force (AFM)
and field emission scanning electron (FE-SEM) microscopy observations with X-Ray diffraction (XRD) and X-ray reflectivity
(XRR) measurements.
[1] T. Minami, J. Oda, J. Nomoto, and T. Miyata, Thin Sol. Films 2010, 519, 385 ; [2] H.S. Huang, H.C. Tung, C.H. Chiu, I.T. Hong, R.Z. Chen, J.T.
Chang, and H.K. Lin, Thin Sol. Films 2010, 518, 6071 ; [3] M.-W.Wua, D.-S. Liub, Y.-H. Su, J. Europ. Ceram. Soc. 2012, 32, 3265.
Buried GaSb junctions controlled by native defects in GaAs/GaSb MOVPE structures
Marco Gornia, Antonella Parisinia, Enos Gombiab, Michele Baldinic, Salvatore Vantaggioa, Carlo Ghezzia,
a
CNISM-Dipartimento di Fisica, Università di Parma, Parma, Italy
b
CNR-IMEM, Parma, Italy
c
Leibniz Institute for Crystal Growth, Berlin, Germany
GaSb is a low-bandgap semiconductor, suitable for the fabrication of photovoltaic (PV) and termo-photovoltaic (TPV) devices
because of its capability to absorb long wavelength radiation from sun as well as from low-temperature blackbody emitters. Thanks
to its direct bandgap (0.72 eV), GaSb shows superior optical absorption properties than Ge (0.66 eV), although the latter has been
largely used as bottom cell material in III-V multi-junction devices by virtue of its almost exact lattice match with (In)GaAs and
InGaP. On the other hand, TPV devices based on GaSb p-n homo-junctions can be successfully fabricated by low cost techniques: a
Zn diffusion into a Te doped substrate has been proposed [1], which takes advantage of a Zn over-pressure in a “pseudo-closed” box
at T ~ 450° C; alternatively, p-n junctions have been obtained by spin coating of the diffusive species compounds [2] and epitaxial
growth [3]. From a theoretical point of view, the process of Zn diffusion into Te-doped GaSb substrates has been investigated in
details by several authors. In particular Sunder et al. [4], demonstrated the influence on such process of the Ga self-diffusion. The
model for the Zn and Ga diffusion proposed by these authors involves stoichiometric defects, such as Ga-vacancy, Sb-vacancy, GaSb
antisite, whose concentration in the lattice is influenced by stoichiometric deviation toward either Ga-rich or Sb-rich growth
38 [1] Bett A.W., Sulima O.V., Semicond. Sci. Technol. 2003, 18, S184–S190 ; [2]Dakshinamurthy S., ShettyS. et al., J. Electron. Mater.2009, 28, 355 ; [3] Andreev V.M.,
SorokinaS.V. et al., Semiconductors 2009, 43, 668–671 ; [4] Sunder K.,Bracht H., Physica B2007, 401-402, 262 ; [5] Hu W.G., Wang Z., et al., Phys. Lett. A 2004,332, 286 ; [6]
Polyakov Y., Pearton S.J., et al., Appl. Phys. Lett.1992,60, 1318 ; [7] Parisini A., Baldini M., et al., J. Appl. Phys. 2013, 113, 043719 ; [8] Baldini M., Gombia E., et al.,
“Admittance spectroscopy on buried GaSb junctions due to defect distribution in GaAs/GaSb MOVPE heterostructures”, J. Appl. Phys, in press.
ZnO nano-tetrapods as 3D charge collection and transport channels in SnO2 based
Pradeep Uththamawadu, Nicola Coppedè, Marco Villani, Davide Calestani, Roberto Mosca, Paolo Fedeli, Andrea
Zappettini
Develop new composite photoanode is a promising way to overcome efficiency enhancement limitation [1,2,3] and long term
stability backs [4] in TiO2 nanoparticles/ Ru dye (cis-di(thiocyanato[N-bis(2-2-bipyridyl-4,4-dicarboxylic acid)]Ru(II)) based solar
cells. In This work we prepared new Dye-Sensitized photo-electrochemical cell (DS PEC), in which photoanode is based on
composite material of SnO2 nano-particles (SnO2-np) and ZnO nano-terapods (ZnO-ntp). The cell results well improved in all
parameters including power conversion efficiency (PCE) and rectification behaviors. When device is fabricated only with ZnO-ntp, it
does not produced good PCE, due to lack of dye adsorption and to damages of the tetrapodes surface by acidic nature of Ru complex
dye.We first realize a device fabricated only with SnO2-np had an Voc of 0.365 V, a short circuitcurrent density (Jsc) of 3.2 mA/cm2
and a FF of 32.2%, resulting in a power conversion efficiency (PCE) of 0.37%. Then To overcome poor inherent properties of SnO2np and ZnO-ntp, we investigated SnO2-np:ZnO-ntp composite photoanode and demonstrated dramatic enhancement of conversion
efficiency (η) and cell stability. The DSSC fabricated with with ZnO-ntp and SnO2-np had Voc, Jsc, FF and η of 550 V, 12.4 mA/cm2,
32 % and 1.95 % respectively. Device performances of the SnO2 coated ZnO-ntp electrodes were found to be highly dependent on
the SnO2 amount and the variation of the cahrateriscis of the cells were studied. The optimal SnO2 amount was found 0.875%
(w/w). while succesive increase further, decreases the Voc and fill factor (FF) rapidly. However, Isc was found to decrease gradually
as the amount of SnO2-np increases. While SnO2-np were found to be highest in dye adsorption amounts and ZnO-ntp was very much
poor in adsorbing dyes, the device fabricated with SnO2:ZnO-ntp composite present better results. This could be due to the injected
photoexcited electrons (hot carriers), which have not relaxed to CB of SnO2 and could also be driven to the CB of ZnO-tp in its
vicinity, without travelling across the several SnO2 nano-particles rich of grain borders. As a result photogenerated charges are
widely separated by ZnO barrier and the recombination is minimized. On the other hand, the 1-D nano nature of the ZnO-ntp
facilitates the transport medium in the photoanode transport of collected photogenerated electrons towards the FTO immediately.
Hence observed higher Jsc, FF and VOC for photoanode fabricated with ZnO-tp:SnO nanoprticles could be justified. When SnO2
amount is increased beyond the optimum amount, PCE of the cell is reduced because recombination process is promoted by direct
electrical paths between FTO and SnO2 are dominant.
[1] S. Ito, M.K. Nazeeruddin, S.M. Zakeeruddin, P. Péchy, P. Comte, M. Gratzel, T. Mizuno, T. Koyanagi, Int. J. Photoenergy, 2009, 51, 7609 ; [2] G. Hodes, I.D.J. Howell,
L.M. Peter, J. Electrochem. Soc. 1992, 139, 3136 ; [3] M. Gratzel, Nature, 2001, 414, 338 ; [4] H.G. Agrell, J. Lindgren, A. Hagfeldt, Solar Energy, 2003, 75, 169
Material Challenges for high reflectivity in non-imaging concentrator optics"
Marco Stefancich
39 Poster Session Material engineering for PhotoVoltaic conversion in the world of 1 $/W silicon panels conditions. Among these defects, the GaSb antisite has a particular relevance, because it is recognized as the defect responsible of the
p-type conductivity in not intentionally doped GaSb [5]. In bulk single crystals, the background native acceptors are present in
density of a few 1017 cm-3. It has been even shown that an unintentional activation/enhancement of these native defects can be
induced by thermal treatments, even giving rise to an unexpected change of conductivity in Te-doped GaSb [6,7]. The samples
studied in this work were obtained by MOVPE deposition of a heavily Zn-doped GaAs layer on a Te-doped GaSb wafer, which is
expected to induce a p-type surface layer in the n-type substrate, through the Zn diffusion activated by the growth temperature. The
aim of such structure was to form a GaSb bottom cell during the stacking of a sequence of properly doped GaAs layers, so that to
obtain, in total, a monolithic tandem GaAs/GaSb cell. However, the analysis of the electrical (by current-voltage, capacitancevoltage, admittance spectroscopy measurements) and structural (by EBIC, SIMS investigations) properties of the buried GaSb
homo-junction, obtained by removing the overgrown GaAs layer, permitted to point out that its formation resulted controlled by
native acceptor defects rather than by the Zn diffusion front [7,8]. The unexpected effect seems to arise from thermal treatments
performed on the GaSb surface before the growth of the epitaxial GaAs layer, which probably generated Sb vacancies at the top
surface of the substrate. Ga-rich lattice conditions should be so realized at the GaAs/GaSb interface [7,8]. The key phenomenological
findings of the work were (i) the comparison between SIMS and EBIC results, which revealed that the p-n junction is not controlled
by the Zn diffusion front but by other unintentionally induced acceptor defects, and (ii) admittance spectroscopy investigation, which
detected a high density of defects having activation energies comparable to those of the GaSb native defects in GaSb. The main goal
of this study is the evidence of a correlation between the pre- and post-growth thermal treatments and the formation/evolution of
native defects, which significantly influence the electrical properties of this compound. We also highlight that the issues pointed out
by this work can give useful information to better understand the mechanisms connected with the formation of the GaAs/GaSb
interface and to optimize the GaAs-on-GaSb epitaxial deposition. New admittance spectroscopy data, which point out the presence of
the native antisite defects, will be here discussed and the current-voltage characteristics analyzed as a function of the temperature.
Masdar Inst. of Science and Tech., Dept. of Mechanical and Material Engineering, Abu Dhabi, United Arab Emirates
Non-imaging concentrators, based on the concept of Winston cone, allow attaining radiation concentration and optimal energy
transfer while maximizing the system acceptance angle.
This is of the outmost importance in several fields ranging from concentrated solar power, concentrator photovoltaic, led illumination
systems and many more. In this process, however, many high angle reflections of radiation on the concentrator surface are involved
both in the case of hollow or Total Internal Reflection concentrators. This requires the development of novel materials for coatings
providing high reflectivity themselves or capable of protecting existing highly reflective, but easily tarnished or scratched, surfaces.
Low temperature deposition approaches, like Pulsed Electron Deposition, of dielectric materials may offer the necessary combination
of chemical stability, hardness and processability due to the wide range of available complex materials.
Investigation on this subject will be presented.
Tuning the work function of graphene with a high molecular weight electron acceptor
Poster Session Organic and hybrid materials Marco Vittorio Nardia, Christos Christodouloua Giovanni Ligorioa, Martin Oehzeltb, Melanie Timpela, Kaled Parvezc,
Klaus Müllenc, and Norbert Kocha,b
a
Humboldt-Universität zu Berlin, Institut für Physik. Brook-Taylor-Str. 6, 12489, Berlin, Germany
b
Helmholtz-Zentrum Berlin für Materialien und Energie, Albert-Einstein-Straße 16, 12489 Berlin, Germany
c
Max Planck Institut für Polymerforschung, Ackermannweg 10, 55128, Mainz, Germany
Graphene is a candidate for a transparent electrode material in next generation (opto)electronic devices. Chemical vapour deposition
on copper foil results in large-area polycrystalline graphene sheets with very good structural and electronic properties. These sheets
can easily be transferred to any substrate of interest [1]. To employ Graphene as a transparent electrode in organic electronic devices,
such as light emitting diodes and solar cells, its work function needs to be matched to the hole and/or electron transport levels of the
organic semiconductors in order to minimize charge injection barriers. One way to tune the work function of various materials is to
deposit a strong electron acceptor or donor molecule that undergoes charge transfer on the surface and thus induces dipoles. A
drawback of the strongest suitable electron acceptor [tetrafluoro-tetracyanoquinodimethane (F4TCNQ)] is its high volatility that
renders it unpractical for applications. We circumvent this problem by using hexaazatriphenylene-hexacarbonitrile (HATCN), a
strong molecular acceptor with high molecular weight (384 g/mol). We show that the work function of graphene on glass can be
tuned continuously from 4.3 eV to 5.5 eV upon depositing HATCN (see figure). A charge transfer type interaction is verified by a
low binding energy emission in the N 1s core-level region measured by X-ray photoelectron spectroscopy (XPS). Near edge X-ray
absorption fine structure (NEXAFS) spectroscopy indicates a flat-lying arrangement of HATCN up to a nominal mass-thickness of
3Å and a coverage-dependent re-orientation from flat-lying to vertically inclined HATCN for higher mass-thickness (figure), in
analogy to results reported for HATCN deposited on Ag surfaces [2].
[1] Li, X. S. et al.; Science 324, 1312–1314 (2009) ; [2] Bröker B.et al.; Phys. Rev. Lett. 104, 246805 (2010)
Organolead halide perovskites for all-solid-state sensitised solar cells
Paolo Fedeli,a, Francesco Gazza,a,b Davide Calestani,a Lucia Nasi,a Patrizia Ferro,a, Tullo Besagni,
Gianluca Calestania,d,Paola Ceronib,Roberto Mosca,a
a
b
Department of Chemistry ''G. Ciamician'', University of Bologna, Bologna, Italy
c
Institute of Physics, Academy of Sciences of the Czech Republic, Prague, Czech Republic
d
Department of Chemistry GIAF, University of Parma, Parma, Italy
a
Pavel Hubikc,
40 E-mail: [email protected]
Recent reports of high conversion efficiencies (up to 15%) for solid-state solar cell devices based on hybrid organic-inorganic
perovskites (CH3NH3)PbI3-xXx (X=I, Br, Cl) make these materials very promising as light-harvesting materials for mesoscopic solar
cells. Although hybrid lead halide perovskites were discovered many decades ago [1] they have been employed as active components
of solar converting devices only in 2009, when TiO2 sensitization by the MAPbBr3 and MAPbI3 perovskites (MA=CH3NH3) was
demonstrated in photovoltaic cells using liquid redox electrolyte [2] achieving an efficiency of 6.5% [3], but the liquid electrolyte
was observed to dissolve the hybrid perovskite in a few minutes. In 2012 CH3NH3PbI3-sensitized all-solid-state solar cells (SS-SC)
with efficiency  larger than 9% were reported[4]. Shortly after a “meso-superstructured” SS-SCs based on a iodide/chloride mixedhalide perovskite MAPbI3-xClx with efficiencies up to 12.3% was demonstrated [5,6], thus pointing out that mixed halide perovskites
may be suitably used to improve the performances of existing solar cells as well as conceive novel photovoltaic devices. Besides, the
chemical management of MAPbI1−xBrx allows the material bandgap to be controllably tuned so that almost the entire visible
spectrum can be covered by this mixed halide perovskite, which enables the realization of colorful solar cells [7]. In all these works
the perovskite pigment has been deposited in a single step onto mesoporous metal oxide films using mixtures based on lead and
methylammonium iodide in common solvents. Very recently a power conversion efficiency of 15% was obtained by using the
CH3NH3PbI3 perovskite prepared through a two step dipping procedure [8]. The above results confirm the potential of these materials
in photovoltaic applications, but at the same time points out that enhancing the photovoltaic performances requires a proper choice of
the material combined with the optimization of its functional properties which strongly depend on the synthesis procedures. Thus
clarifying the relation between material properties and the procedures used for their preparation is of fundamental importance for
light harvesting optimization and cell efficiency increase. Indeed, despite the widening literature on the photovoltaic use of hybrid
lead perovskites, many questions remain to be addressed regarding the diverse structural chemistry of these materials and the nature
of charge transfer, before it will be possible to rationally modify and tailor chemistries and nanostructures in solar cells to improve
solar cell performances.
In this communication we report about the influence of the preparation procedures on the properties of lead-based hybrid halide
perovskites, in particular methylammonium triiodoplumbate (MAPbI3) films and mixed lead halide perovskites having different
I:Br(Cl) ratios. We investigate the role of solvents and self-assembling process parameters (temperature, time, …) in determining the
morphological, crystallographic, optical and electrical properties of the obtained materials. The aim is identifying the procedures
most suited to reproducibly prepare hybrid lead perovskites having the capability of both light absorption and charge transport within
a mesoporous network combined with enhanced dye loading for the most efficient sunlight harvesting. Issues related with dye
loading are also discussed considering the infiltration of the obtained perovskites into photoanodes made of either nanostrucutred
TiO2 or porous nanosheets of ZnO, which is considered an environmental friendly and low-cost potential alternative to TiO2.
Functionalization of SiC Nanowires by Supersonic Molecular Beams for Photodynamic Therapy
Roberta Tatti1, L. Aversa1, R. Verucchi1, F. Fabbri2, F. Rossi2, G. Attolini2, M. Bosi2, G. Salviati, S. Iannotta2
1
IMEM-CNR, Povo(Trento), Italy
2
IMEM-CNR –Parma, Italy
Photodynamic Therapy (PDT) is a therapeutical approach in the cancer treatment, which consists in the activation of a
photosensitizer (mainly phorphyrins) with visible light in order to produce oxygen reactive species, in particular 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), in which the NWs are activated by
the x-ray radiation and transfer energy to the molecules, that will be able to produce the singlet oxygen. 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, a class of macrocycle molecules showing a good match between the organic
absorption Q band and the 3C-SiC near-band-edge-optical 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 [2] 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 [1], 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 [3]. 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.
41 Poster Session Organic and hybrid materials [1] Weber, D. Z. Naturforsch 1978, 33b, 1443 ; [2] Kojima A., Teshima K., et al., J. Am. Chem. Soc. 2009, 131, 6050 ; [3] Im J.H., Lee C.R., et al.,
Nanoscale 2011, 3, 4088 ; [4] Kim H.-S., Lee C.R, et al., Sci. Rep. 2012, 2, 591 ; [5] Lee M. M., Teuscher J, et al., Science 2012, 338, 643 ; [6] Ball
M., Lee M. M., et al., Energy & Environmental Science 2013, 6, 1739 ; [7] Noh J. H., Im S. H., et al., Nano letters 2013, 13, 1764 ; [8] Burschka J.,
Pellet N., et al., Nature 2013, 316, 499.
[1] F. Fabbri et al., Nanotechnology 21, 345702 (2012) ; [2] M. Bruchez et al., Science3 281, 2013 (1998) ; [3] M. Nardi et al., Phys. Rev. B 79,
125404 (2009)
Crystalline rubrene in epitaxial heterostructures
Luisa Raimondoa, Marcello Campioneb, Enrico Fumagallia, Massimo Moreta, Alessandro Borghesia, Adele Sassellaa
b
a
Among organic semiconductors, the orthorhombic polymorph of rubrene single crystal is one of the most promising, since it displays
the record hole mobility and exciton diffusion length. In view of the development of rubrene based devices, highly crystalline thin
films with the same structural properties of the single crystal would be the proper choice. In this respect, huge efforts have been made
by many research groups with poor results since rubrene possesses a high propensity to grow amorphous on most substrates, in
particular on those technologically relevant, e.g. silicon dioxide. Here, we show that, contrarily to what is reported in the literature
about most of the attempts, rubrene spontaneously crystallizes on organic crystalline substrates when exploiting the mechanisms of
organic epitaxy [1], without any external treatments. In particular, we discuss the growth of organic heterostructures between rubrene
and another organic semiconductor, namely α-quaterthiophene (4T), on an insulating organic single crystal substrate (potassium
hydrogen phthalate, KAP) by organic molecular beam epitaxy. Whilst rubrene films grown on KAP are amorphous, the combination
with 4T drives a spontaneous formation of crystalline RUB films displaying the orthorhombic polymorph structure and a peculiar
orientation with respect to 4T and, thus, KAP. In particular, the change of the sequence of the deposited layers on KAP (RUB on 4T
or viceversa) results in completely different growth dynamics of RUB, where structural transitions can even take place, as deduced
by morphological, structural and optical studies [2,3].
[1] Sassella A., Campione M., et al., Riv. Nuovo Cimento 2008, 31, 457 ; [2] Raimondo L., Fumagalli E., et al., J. Phys. Chem. C 2013, 117, 13981 ;
[3] Sassella A., Raimondo L., et al., Adv. Mater 2013, 25, 2804.
Poster Session Organic and hybrid materials Investigation of the spatial inhomogeneity of the photoluminescence and photovoltaic properties of inverted all
polymer solar cells by confocal spectroscopy
Andrea Perullia, Sandro Lattanteb, Anna Persanoc, Adriano Colac, Massimo Di Giuliob and Marco Annib
Dipartimento di Ingegneria dell’Innovazione, Università del Salento, Lecce, Italy
b
Dipartimento di Matematica e Fisica “Ennio De Giorgi,” Università del Salento, Lecce, Italy
c
IMM-CNR, Istituto per la Microelettronica e Microsistemi, Lecce, Italy
a
The most efficient polymer solar cells have been fabricating using a mix of polymers (electron donor) and fullerenes (electron
acceptor). However, it has been recently demonstrated that polymer:polymer solar cells, employing polymers also as electron
acceptors, are very promising systems, thanks to the higher flexibility in the energy band engineering, which allows a better matching
of the solar spectrum and the possibility of realization of all-plastic solar modules [1-2]. Concerning the device structure, it has been
demonstrated that the use of the so called inverted structure, in which the metal electrode is used to collect holes, present a much
higher operational stability than standard cells, thus allowing a higher device lifetime. However, despite these advantages, devices in
standard configuration have been investigated in the most of works reported in literature until now. In this work, all polymer
inverted solar cells based on a blend of regioregular poly(3-exylthiophene) (rrP3HT) and poly(9,9-dioctylfluorenecobenzothiadiazole) (F8BT) were fabricated and characterized by confocal laser scanning microscopy (simultaneous
photoluminescence (PL) and external quantum efficiency (EQE) mapping). The device was fabricated on cleaned fluorine-doped tin
oxide (FTO) covered glass substrates, A thin layer (~80 nm) of zinc oxide (ZnO) nanoparticles (used as an electron selective layer)
was deposited by spin-coating onto the substrates from a water-dispersion (Sigma Aldrich Zinc oxide dispersion nanoparticles 50
wt.% in water, average particle size ~35 nm) at 6000 rpm for 60 s. A chlorobenzene solution of a blend of rrP3HT:F8BT=60:40 by
weight (total concentration of 30 mg/ml) was prepared and stirred overnight at ambient condition (F8BT was purchased from the
American Dyes Source, Inc. while rrP3HT from Rieke Metals); the polymer blend films (~150 nm) were spin-coated onto the ZnO at
800 rpm for 30 s. Finally, the silver top electrodes (~100 nm) were thermally evaporated onto the active layer at a rate of 0.1 nm/s.
The device was annealed in air at 150 °C for 20 min after the evaporation of Ag. Figure 1 reports the typical F8BT PL (a), rrP3HT
PL (b), and EQE (c) maps of a 600 µm x 600 µm region. Comparing the two PL maps, a non-complementarity of the F8BT and
rrP3HT PL is observed with common regions of high PL intensity. This result points out that inhomogeneities of the PL maps are not
due to microscopic phase separation of the two polymers, but rather to some regions, on the scale from tens to hundreds of microns,
with different submicrometric polymer arrangement. On the other hand, a clear complementarity of the two PL and EQE signals is
observed with low EQE in the high PL regions and vice versa.
42 Fig. PL and EQE maps of the rrP3HT:F8BT blend for a sample region of 600 µm x 600 µm ((a) F8BT PL map, (b) rrP3HT PL map, (c) EQE map))
In conclusion, we fabricated inverted all polymer organic solar cells and we investigated their optical and photoelectric properties by
confocal spectroscopy. We observe a strong non-uniformity of the charge generation due to the existence of large (up to ~100 µm)
scale domains with locally different rrP3HT:F8BT submicrometric order. A clear non-uniformity of the charge collection efficiency
is also observed on a similar scale, indicating that the correlation between the macroscopic device properties and the local properties
of the active material cannot be limited to the sub-micrometric or micrometric scale, as generally reported in literature. Hence, the
presented results point out that a great care should be dedicated to the uniformity of both the active layer and the electrodes on a scale
comparable to that of the whole polymer solar cell.
[1] M. Shin et al., Materials Science and Engineering B, 176, 382-386, 2011 ; [2] Y. Kim et al., Chemistry of Materials, 16, 4812-4818, 2004 ; [3]
MC. McNeill et al., Nano Letters 4, 2503 (2004).
The polymorphism of TPB
Domenico Crocco, Alessia Bacchi, Mauro Carcelli, Alberto Girlando, Matteo Masino.
Dipartimento di Chimica Parma University, Viale delle Scienze 17/A, 43124 Parma
[1] Alessia Bacchi, Ivano Bilotti, Aldo Brillante, Domenico Crocco, Raffaele G. Della Valle, Alberto Girlando, Matteo Masino, Paolo Pelagatti, and
Elisabetta Venuti., Journal of Raman Spectroscopy 2013, 10.1002/jrs 4278.
Epitaxial growth of hexathiophene polymorphs on β-alanine(010) single crystals
Silvia Trabattoni a, Massimo Moreta, Marcello Campioneb, Luisa Raimondoa, Adele Sassellaa
Department of Materials Science, University of Milano-Bicocca, Milano, Italy
b
Department of Earth and Environmental Sciences, University of Milano-Bicocca, Milano, Italy
a
43 Poster Session Organic and hybrid materials TPB (1,1,4,4-tetraphenyl-1,3-butadiene) is a luminescent molecule that displays luminescence in the crystalline state, when
favourably packed by aligning the transition dipoles in the correct orientation. TPB is currently known in four polymorphs α, β,
γ,δ[1], and TPB molecular structure approximately displays C2 point symmetry in the α form, and Ci point symmetry in β and γ.
Among these the β form has proved to be best suited to photoluminescence; unfortunately its crystallization is not reproducible. The
γ form, structurally very similar to the β polymorph, is also rarely obtained. It is therefore advisable to develop new crystal forms of
TPB (polymorphs, co-crystals, solvates) by using the tools of crystal engineering in order to optimize photoluminescence for the
design of light emitting or photovoltaic devices.
We have explored the polymorph landscape of TPB by several techniques, such as crystallization solvent screening, gel
crystallization, temperature controlled precipitation, melt quenching, recrystallization from the melt, sublimation, affording mostly
the commercial α phase and sometimes the less stable γ phase, or a cyclohexane solvate with interesting solid/vapour exchange
properties. Most imporantly, by critical inspection of DSC traces we have discovered that immediately after melting, the commercial
α phase recrystallizes in a new polymorph δ, previously unknown, with Z’=1.5 and comprising both previously known conformers of
TPB. This points to the presence of polymorph impurities in the commercial product, that seed the crystallization of the δ phase.
However, we discovered that after melting of the α phase is possible to obtain two different polymorphs by different cooling rate, in
fact, if the melt is cooled at a cooling rate less than 0.5 C / min we get the α phase, if the cooling rate is more than 0.5 C / min we get
the δ phase, this means that the thermodynamic phase is α, and the kinetic phase is the δ, this experimental result is confirmed by the
calculations. The structural basis of this intriguing polymorph landscape are discussed. Unexpected behaviour of seeding experiments
on the melt will be also discussed and rationalized by means of structural analysis and of PXRD, DSC, Raman, SS-NMR
experiments.
The control of crystal characteristics, such as morphology, size, and polymorphism, is a nodal point because they influence, for
example, solubility, processability, mechanical properties, electrical properties, and bioavailability. Organic materials are prone to
crystallize in different polymorphs, owing to their typical weak intermolecular interactions in the solid state. The formation of several
different polymorphs originates from the rather small difference of the activation energies for nucleation of the various crystal forms
[1]. The crystallization of a metastable polymorph is a consequence of kinetic selectivity during nucleation and growth, being the
differences in the packing energies among polymorphs very small [2]. Single crystals of a well-known amino acid, namely β-alanine
(β-ala) [3], were exploited as a novel substrate for the deposition of thin films of organic molecules suitable for optoelectronic device
applications. The β-ala(010) surface properties were investigated in terms of polymorph selectivity, by depositing thin films of
hexathiophene (6T), one of the most studied organic semiconductors. Although two 6T polymorphs are known [4,5], 6T films grow
as crystalline on organic crystal substrates in the low temperature (LT) polymorph with different contact planes: 6T/LT(100) domains
with molecules upright standing and 6T/LT(010) crystallites with molecules laying almost flat on the substrate. The morphology, the
crystal structure, and the orientation of the films, deposited by organic molecular beam epitaxy (OMBE), were analyzed by atomic
force microscopy, X-ray diffraction, and UV-Vis spectroscopy. The experimental results are compared to computational simulations
of the 6T/β-ala(010) interface, demonstrating that β-ala induces the growth of both the mentioned 6T polymorphs [6]. Moreover, the
6T/LT(010) crystallites grow in large amount thanks to their adhesion energy higher than that of the 6T/LT(100) ones. β-ala, a lowcost, biocompatible, and highly water soluble material, can then be employed to grow metastable polymorph overlayers of
technological interest, that can easily be wet-transferable on other substrates.
[1] Bernstein J. Polymorphism in Molecular Crystals. Oxford University Press, Oxford 2008 ; [2] Carter P. W., Ward M. D. J. Am. Chem. Soc. 1994,
116, 769 ; [3] Papavinasam E., Natarajan S., Shivaprakash N. C. Int. J. Pept. Protein Res. 1986, 28, 525 ; [4] Horowitz G., Bachet B. et al., Chem.
Mater. 1995, 7, 1337 ; [5] Siegrist T., Fleming R. M., et al., J. Mater. Res. 1995, 10, 2170 ; [6] Trabattoni S., Moret M., et al., Cryst. Growth Des.
2013, DOI: 10.1021/cg400481h.
Epitaxial interfaces in pentacene/perfluoropentacene thin film heterojunctions
Luisa Raimondoa, Marcello Campioneb, Katharina Brochc, Frank Schreiberc, Adele Sassellaa
b
c
Universität Tübingen, Institut für Angewandte Physik, Tübingen, Germany
Poster Session Organic and hybrid materials a
π-conjugated organic semiconductors are widely used in thin film form as active components in optical, opto-electronic and electrical
devices. In this respect, a fundamental aspect is to achieve a complete knowledge and control of the growth mode of these materials
depending on the growth method, the substrate, and the temperature used. For those devices where transport properties have to be
optimized (field-effect transistor, photovoltaic cells, etc.), the main issue is to achieve a fine control on morphology, crystalline
structure and quality of the interfaces involved. Using organic crystalline layers as substrates for templating the growth of highly
ordered phases of the overlayer (organic-organic epitaxy [1,2]) is the most proper strategy for fulfilling this condition.
Here, we report a study on heterostructures based on pentacene (PEN, C22H14) and perfluoropentacene (PFP, C22F14), p- and n- type
organic semiconductors, respectively, grown by organic molecular beam epitaxy on an organic single crystal, namely potassium
hydrogen phthalate (KAP). Starting from the single-component films on KAP, we explored the interface properties of the
heteroepitaxial films between PEN and PFP by means of a combined analysis of the morphological, structural and optical properties.
On the basis of the experimental results, we provide a description of the film phases present in the heterostructure as well as the
azimuthal orientation of one layer with respect to the layer underneath.
[1] Sassella A., Campione M., et al., Riv. Nuovo Cimento 2008, 31, 457 ; [2] Hinderhofer A., Schreiber F., ChemPhysChem 2012, 13, 628.
Organic electrochemical transistor on cotton fiber as sensor for application in human sweat
Nicola Coppedè, Giuseppe Tarabella, Marco Villani, Davide Calestani, Roberto Mosca, Salvatore Iannotta, Andrea
Zappettini
Recently the functionalization of cotton yarns (natural cellulose) have been successfully used to realize conductive fibers, which have
been applied as innovative textile-integrated sensing devices. Among the different approaches for the realization of the active layer
on textile yarns, conductive polymeric materials [1], metal nanoparticles, [2] or carbon nanotubes (CNTs) [3], have been successfully
used. In particular the ability to make active polymeric layers based on conductive polymer film of poly(3,4-ethylenedioxythiophene)
doped with poly(styrene sulfonate) (PEDOT:PSS), a p-type organic semiconductor, over cotton treats, with appropriate
morphological and structural characteristics, allowed to produce an innovative class of sensing devices with biomedical, healthcare
and sports applications. Conductance per length unit (up to 10-1 S cm-1) resulted matching the needs to realize Organic
Electrochemical Transistor (OECT), which could be used as sensing device directly integrated on textile structures. The output
characteristics of cotton yarn OECT has been demonstrate for the first time using a gel electrolyte for ionic exchange [2]. In this
44 work we present a simple and direct solution to integrate OECT in textile structure with directly application liquid solutions [1] and
we applied in monitoring the saline concentration in human sweat. The results on textile structures are promising toward important
applications for commercial and industrial solutions, especially considering data acquired in human biological fluids, such as sweat
or saliva, as monitoring information in physiological state and sports performances.
Despite of an adequate sensitivity and a very simple and handily structure, OECT on textile present limitations in the selectivity and
in the recognition of different molecular species. To overcome these limitations a simple approach is developed on cotton OECT,
based on the different materials for gate electrode. In such a way different reaction, depending on the species in the electrolyte, could
be promoted, improving the selectivity of the device. Portable sensing device could be used to control the performances of athletes
during performances or to control workers during high stress situations, improving control and safety with non-invasive systems.
[1] Giuseppe Tarabella, Marco Villani, Davide Calestani, Roberto Mosca, Salvatore Iannotta, Andrea Zappettini and Nicola Coppedè J. Mater.
Chem., 2012, 22, 23830 ; [2] Giorgio Mattana, Piero Cosseddu, Beatrice Fraboni, George G. Malliaras, Juan P. Hinestroza, Annalisa Bonfiglio,
Organic Electronics 2011, 12, 2033–2039 ; [3] Tomàs Guinovart, Marc Parrilla, Gastón A. Crespo, F. Xavier Rius and Francisco J. Andrade Analyst,
2013, 138, 5208-5215
Pentacene thin films growth: optical properties from sub-monolayer up to the bulk
Mattia Marchio1, P. Bettotti2, S. Iannotta1, T. Toccoli1
IMEM-CNR, Istituto Materiali per Elettronica e Magnetismo Via alla Cascata 56/C, Povo Trento, Italy
2
Laboratorio Nanoscienze, Dipartimento di Fisica, Università di Trento Via Sommarive 15 Povo Trento, Italy
1
Antibody functionalized iron oxide nanoparticles loaded to improve drug delivery for tumor care
Luca Dalboscoa, S. Tongb, G. Baob, V. Antoninic, M. Dalla Serrac, R. Morrigld, D. Maniglioa, C. Migliaresia
University of Trento, Trento
b
Georgia Institute of Technology and Emory University, Atlanta, USA
c
FBK-CNR, Trento, Italy
d
LBI-CR, Wien, Austria
a
Nanoparticles synthesized with different methods and from different materials have shown two fundamental characteristics. First,
their properties are size-dependent. Second, the surface-to-volume ratio can reach significant values: the nanoparticle surface is very
reactive and thus can be used as a vector for other types of molecules or biomolecules.
For these applications, magnetic iron oxide nanoparticles (or MNP) showed excellent properties in the therapeutic area as drug
carriers (drug delivery), as vectors to increase the local temperature (hyperthermia) and in the diagnostic area as contrast agent for
45 Poster Session Functional nanostructures The interest towards organic electronics in the lasts years is acquiring great importance, taking to a more accurate research on the
properties and possibilities that those materials offer to us. This success is due to the good intrinsic properties that those materials
have, such as: large flexibility in applications, chemical engineering and bio-compatibility. Those properties can take to the
development of devices with interesting characteristic in the world in which the inorganic electronics based on silicon does not have
enough good functionality such as in the case of the realization of sensors and or in the case of electroluminescent devices (just think
at the realization of AMOLED screen for mobile phones, or the bio-applications typical of organic sensors).
To obtain devices that are able to take advantage of the properties of organic materials, there are some important aspect to know,
overcome and improve; in particular one of the more important aspect is understanding how the semiconductor material grow on the
surface of the device, and how those molecules interact with the surface. So, studying the process of assembling (growth of the
materials on the surface) and the interactions between molecule and surface can take to understand the realization of devices in a
better way.
To this end we grown pentacene on silicon/silicon oxide surface using a technique that permit to achieve the better order in the thin
film growth based on inseminated supersonic beams (SuMBD). The aim of this study was the observation of the optic and electric
properties of thin films made of pentacene and how those properties changes during the growth process. Especially we focus our
attention on the optical properties within the range 1.45 and 4.0 eV with ellipsometric analysis, starting with the formation of the first
layer up to the bulk phase. Ellipsometry allowed us to study how parameters n and k change depending on the thin film thickness.
obtaining important information about the type of interactions that exist between the surface and the molecules from the growing
film.
Results show how the characteristic peaks of the pentacene absorption spectrum moving proportionally with the increase of the
thickness. The firsts layers, the most important for the electrical transport, are strong affected by the interaction with the surface. This
fact is clear in all the optic transitions of Pentacene, not only those are related to the formation of the film.
The study is correlated by morphological (made by AFM - Atomic Force Microscope) and photoluminescent analysis. The
morphological analysis showed a growth nearly layer by layer for the firsts layer which have shown to be extremely ordered in
according to the results of the study of the curves of the characteristic peaks of luminescence.
magnetic resonance imaging (MRI). This work has been focused on the production, characterization and functionalization of iron
oxide nanoparticle and their effectiveness tests in vitro and in vivo. [1][2]
The magnetic core of iron oxide has been synthetized by thermo-decomposition of iron complex in a mixture of oleic acid and
oleylamine, then coated with polyethylene glycol to make nanoparticles stable in water and monodisperse. The NPs have been
characterized using dynamic light scattering (DLS), transmission electron microscope (TEM) and X-ray Photoelectron Spectroscopy
(XPS). [3][4]
The size distribution of NPs resulted to be very narrow with an average diameter of about 25 nm and a core of 6.5 nm. This size is
compatible with the exploitation of the EPR effect (enhanced permeability and retention) of a tumor tissue, where the porosity of
endothelium near the tumor region can reach up to 1000 nm instead of the 10 nm porosity of the healthy tissue.
Different coating procedures have been used to improve stability, functionalization and production.
To improve the tumor targeting and the uptake of MNP by cancer cell, nanoparticles have been functionalized with an antibody
against a specific epidermal growth factor receptor (EGFr) expressed by tumor cells. To verify the effectiveness of targeting and to
compare the uptake of nanoparticles with and without antibody, several cell lines with different EGFr gene expression have been
used. The in vitro and in vivo data showed that the different types of MNP with AB entered more easily the cell with higher gene
expression respect to MNP without AB.
As further step NP has been loaded with doxorubicin (commonly used chemotherapy drug), the effectiveness of the drug has been
tested in vivo and results show that the Doxorubicin-MNPs reduce growth and proliferation of tumor.
[1] Tong S., et al., Nano Lett. 2010, 10, 4607–4613 ; [2] Tong S., et al., Nano Lett. 2011, 11, 3720–3726 ; [3] Speranza G., Dalbosco L., et al.,
Advances in Science and Technology Vol. 76 (2010) pp 165-170 ; [4] Minati L., Dalbosco L., et al., Applied Surface Science 257 (2011) 10863–
10868
Zno nanostructures: electrical and optical properties for gas sensing
Poster Session Functional nanostructures Maria Cristina Carottaa, Ambra Fioravantib, Sandro Gherardib, Cesare Malagùb, Michele Sacerdotib, Stefano Lettieric,
Emanuele Orabonac, and Pasquale Maddalenac
a
CFR, Consorzio Ferrara Ricerche, Ferrara, Italy
b
Università di Ferrara, Dipartimento di Fisica e Scienze della Terra, Ferrara, Italy
c
Università di Napoli “Federico II”, Dipartimento di Fisica, Napoli, Italy
A wide range of technological applications such as photocatalysis, piezoelectricity, optoelectronics, photovoltaic conversion and gas
sensing make ZnO a very attractive material. Moreover, ZnO exhibits high exciton binding energy (60 meV) which causes an
efficient UV emission (~ 380 nm), making it suitable for short wavelength optoelectronic applications. Zinc oxide behaves as n-type
semiconductor (band gap of 3.37 eV) because of stoichiometric defects, in particular oxygen vacancies acting as electronic donor
levels. Zinc oxide also exhibits the feature to be easily synthesized in a large variety of nanostructures such as nanoparticles,
nanowires, nanorods, nanotetrapods, etc., successfully used in gas sensing to detect various gases. In this context, recent works claim
superior performance of mono- and two-dimensional nano-morphologies with respect to traditional round-shaped three-dimensional
nanoparticles [1]. Some of the authors already approached this matter in [2], in which a comparison between round-shaped and twodimensional nanoparticles in form of nanotetrapods (TP) was performed.
This work aims to synthesize zinc oxide nano-powders with different morphologies, using a wet chemical route starting from an
aqueous solution of zinc nitrate hexahydrate for all materials. SEM observations performed onto the synthesized materials
highlighted powders shaped like nano-particles (ZNP), nano-particles assembled in a bipyramidal form (ZBP), nano-needles (ZNN)
and flower-like (ZFL) nanostructures. The powders have been used to deposit thick film layers by means of screen printing
technology onto miniaturized alumina substrates for comparing their functional properties in gas sensing both at operating
temperature typical of chemo-resistive sensors (300 – 600 °C) as well as at room temperature assisted by UV light. The thick films
have also been deposited onto silicon substrates for photoluminescence (PL) characterization. The Arrhenius plots, obtained by
changing the temperature between 100 and 650 °C at the heating rate of 5 °C/min, showed that all films exhibit semiconductor n-type
behavior. Indeed, as for tin dioxide, the inter-grain Schottky barrier formation attributed to a negative surface charge accumulation
(due to surface oxygen adsorption) modulates the film conductivity. Moreover, the two films made up of nanoparticles (ZNP and
ZBP) highlight greater conductivity with respect to the two films constituted by bidimensional structures, ZNN and ZFL, and the
heights of the energy barriers are in agreement with the Schottky barrier model. Indeed, for each couple of samples, a greater
conductivity corresponds to a lower energy barrier. To determine the energy barrier (the difference in energy between the conduction
band bottom at surface and that in the bulk) temperature-stimulated conductance measurements were performed.
Photoluminescence characterizations have been carried out at room temperature in air, exciting the samples through a He-Cd laser at
325 nm and 442 nm of wavelength. All samples exhibit two emissions, one in the UV region and the other in the visible one. In
particular, ZFL and ZNN show the greatest emission intensities in the visible region, a feature that can be related with a higher
cristallinity of the samples. With respect to the UV emission, a variation of the position of the PL peak has been observed for the
different nanostructures, which can be ascribed to a different concentration of native defects [3]. Finally, for all samples the
wavelength of the visible emission is centered in a range from 660 to 680 nm. Differently to PL measurements, ZNP and ZBP (the
films made up of nanoparticles) show the highest responses to the tested gases (acetone, ethanol, acetaldehyde, formaldehyde and
ammonia). Obviously, different factors are bearing on the performances of the optical characterizations with respect to the electrical
ones. Indeed, in the case of the gas responses offered by nanoparticles or nano-bidimensional films, it has been demonstrated that,
when the grain radius reaches dimensions comparable to the depletion region width, the curvature effects lead to the phenomenon of
46 Fermi level unpinning, which improves the sensitivity of the material. The comparison among nanostructures with one, two and three
dimensions showed that the strongest effect is obtained for the 3D case [4] gases
[1] J.G. Lu, P. Chang, Z. Fan, Quasi-one-dimensional metal oxide materials—synthesis, properties and applications, Mater. Sci. Eng. R 52 (2006) 49–
91 ; [2] M.C. Carotta, A. Cervi, V. di Natale, S. Gherardi, A. Giberti, V. Guidi, D. Puzzovio, B. Vendemiati, G. Martinelli, M. Sacerdoti, D.
Calestani, A. Zappettini, M. Zha, L. Zanotti, ZnO gas sensors: a comparison between nanoparticles and nanotetrapods-based thick films, Sensors and
Actuators B, 137 (2009) 164–169 ; [3] A.B. Djurišić, H.H Leung, Optical properties of ZnO nanostructures, Small, 2 (2006) 944 – 961 ; [4] E.
Comini, V. Guidi, C. Malagù, G. Martinelli, Z. Pan, G. Sberveglieri, Z.L. Wang, “Electrical properties of tin dioxide two-dimensional nanostructures”
Journal of Physical Chemistry B 108 (6) (2004) 1882-1887.
Nanostructured Titania: doping, characterization and photocatalytic activity
Fabio Orlandia, Viola Viganòa, Ilaria Alfierib, Andrea Lorenzia,b, Lara Righia,c, Angelo Monteneroa,b
Department of Chemistry, University of Parma, Italy
b
CIPACK, Interdepartmental Center on Packaging, Parma, Italy
c
a
In recent years the attention on nanoscale titanium dioxide is rapidly increased due to its remarkable characteristics, such as
biocompatibility, stability under a wide range of conditions and low costs. Its applications are spreading mainly in the field of
photocatalysis (for the reduction of air and water pollutants) and solar cells (Dye-Sensitized Solar Cells, DSSCs). The main drawback
to the utilization of TiO2 on large scale is its wide band-gap (3.2 eV) that confines its activity only under UV exposure. Aim of last
research is the development of a simple and reproducible way to enhance the activity of titanium dioxide in the visible region [1].
This can be obtained doping the TiO2 nanoparticles with transition metals, anions, dyes and rare earths [2].
In this work a sol-gel synthesis route to titanium dioxide nanoparticles doped with rare earths ions, Nd3+ and Er3+, is shown. XRD
studies indicate the obtaining of nanoscale particles of anatase, in which the lattice parameters distortion seems to be caused by the
presence of, at most, the 2-3 % in mole of Ln3+ ion. Moreover XRD studies show that the doping inhibits, in some extent, the
conversion of anatase to rutile. Diffuse reflectance UV-Visible spectra were used to estimate the new band-gaps of the doped
samples, demonstrating that they are narrow in comparison with the undoped TiO2. In conclusion, colorimetric measurement were
conducted to evaluate the photocatalytic activity in the degradation of methylene blue and rhodamine B. Doped TiO2 demonstrates to
be more efficient than the undoped one, even under the only visible light.
[1] S. Rehman et al., Journal of Hazardous Materials, 170 (2009) 560 ; [2] S. Obregón et al. Journal of Catalysis, 299 (2013) 298
Role of In-Situ Grown SiN Passivation for E-Mode AlGaN/GaN MOSHEMTS on silicon substrate for efficient
power converters
We present enhancement mode (E-mode) Al0.25GaN0.75/GaN metal oxide semiconductor high electron mobility transistors
(MOSHEMTS) with MOCVD-grown (in-Situ) SiN passivation and atomic layer deposited (ALD) gate oxide. By selective removal
of the in-situ passivation below the gate contact, E-mode operation can be achieved [1]. The removal of the 50 nm in-situ SiN
passivation is performed by reactive ion etching with SF6. A thin ZrO2 layer of 10 nm is used as gate dielectric. The oxide is
deposited by ALD at 150 °C using tetrakis(dimethylamido)zirconium(IV) as metal precursor. Schottky barrier (SB) devices are also
used for comparison. Metal insulator semiconductor HEMT (MISHEMT) devices with the gate placed on top of the in-situ SiN were
processed as a reference for the analysis of the as-grown barrier/passivation interface properties.
The SB and MOS devices show E-mode behavior and drain current on/off ratios of 106. The Vth are distributed around 0.75 V. The
equivalent MIS samples with 50 nm SiN show a Vth of -7 V. The oxide inclusion in the MOS devices decreases the gate current
leakage by two orders of magnitude for a gate bias of 1.75 V.
[1] J. Derluyn, M VanHove, D. Visalli, A. Lorenz, D. Marcon, P. Srivastava, K. Geens, B. Sijmus, J. Viaene, X. Kang, J. Das, F. Medijdoub, K.
Cheng, S. Degroote, M. Leys, G Borghs and M. Germain, "Low Leakage High Breakdown E-Mode GaN DHFET on Si by Selective Removal of InSitu Grown Si3N4", in IEDM09-157, 2009.
Vapour Phase Growth of PbO Nanowires with Extreme Aspect Ratio
Giacomo Benassia, Davide Calestania, Nicola Zambellia, Andrea Zappettinia
47 Poster Session Functional nanostructures Mattia Capriotti a, A. Alexewicz a, O. Bethge a, D. Visalli b, J. Derluyn b, C. Fleury a, E. Bertagnolli a, D. Pogany a, G.
Strasser a
a
TU Wien, Floragasse 7, A-1040 Vienna, Austria
b
EpiGaN, Kempischesteenweg 293, B-3500 Hasselt, Belgium
a
Although metal-oxide nanostructures are today widely investigated, lead oxide remain a not completely explored case and their
nanostructures are not frequently reported in literature. Lead and oxygen forms several compounds, differing in stoichiometric ratio
and crystalline structures [1]. Lead monoxide (PbO), for example, is a promising high-Z material for radiation detection. In particular
the availability of single-crystal nanostructures could allow better investigations of transport properties, which is a fundamental
parameter for detectors realization but not well defined for this material. Vapor phase growth process resulted to be the best
synthesis process to obtain PbO nanostructures with the right stoichiometry, as for example nanowires (or better, ”nanoribbons”)
with an extreme length-to-thickness aspect ratio.
[1] D. Risold et al., J. Of Phase Equilibria, vol. 19 No. 3 1998
Local current mapping on polycrystalline sexithiophene thin films by conductive atomic force microscopy
Sreejith Embekkata, Adele Sassellaa, Olivier Douhéretb, Roberto Lazzaronib and Alessandro Borghesia
b
Laboratory for Chemistry of Novel materials, University of Mons, Belgium
a
Poster Session Functional nanostructures In the past few decades, great attention has been devoted to π-conjugated molecules for electronic applications. Among small organic
molecules displaying semiconducting properties, thiophene oligomers and related materials are of peculiar interest for device
applications, provided their ability to locally self-organize. High hole mobility [1] and stability in air, together with demonstration of
prototype devices already made with sexithiophene (6T) [2], make it a particularly interesting material. Yet, in order to precisely
determine how the nanoscale self-organization of the 6T impacts on its electrical properties, high resolution characterization methods
such as conductive atomic force microscopy (C-AFM) can be of great interest [3].
6T thin films have been deposited by organic molecular beam epitaxy (OMBE) on patterned glass/ITO substrates and characterized
by C-AFM. Typical morphologies of 6T thin films on glass and ITO substrates and their electrical responses for negative DC sample
bias are shown in Figure 1 for the films grown on glass (upper row) and those grown on ITO (lower row). The surface morphology is
reported in panels (a) and (d) and the current map in panels (b) and (e), while panels (c) and (f) show zoomed images of both
morphology and current signals. These data show the impact of the grain orientation both on the carrier injection at the tip-sample
contact and on the charge transport within the film. Typical I-V curves collected with different bias polarity and tip location (on
6T/ITO and 6T/glass films) show different dominating charge transport mechanisms. Tunneling, resistive and space charge limited
current (SCLC) mechanisms can be observed, depending on the bias polarity. The occurrence of those mechanisms seems to be
related to film thickness, injection barrier at the ITO/6T contact, and spreading effect at the low-dimension tip-sample contact.
Fig. 1: (a) Height image of a 25 x 25 μm2 area of 15 nm 6T thin film on glass substrate showing background grains and dendritic islands. (b) C-AFM
current image of (a) at -2V dc sample bias. (c) Zoomed height image of the background grains showing terraced pyramidal grains and elongated
grains and their current response on glass. (d) Height image of a 25 x 25 μm2 area of 15 nm 6T thin film on ITO showing background grains and
dendritic islands (b) C-AFM current image of (d) at negative 2 V dc sample bias. (c) Zoomed height and current image of the background grains on
ITO.
[1] Torsi, L.; Dodabalapur, A.; Rothberg, L. J.; Fung, A. W. P.; Katz, H. E. Phys. Rev. B 1998, 57, 2271 ; [2] Stallinga, P.; Gomes, H. L.; Biscarini,
F.; Murgia, M.; de Leeuw, D. M. J. Appl. Phys 2004, 96, 5277 ; [3] Moerman M., Lazzaroni R. Douhéret O., Appl. Phys. Lett. 2011, 99, 093303.
48 Synthesis of lithium intercalated fullerene and fullerane for applications in Li-ion batteries
Giovanni Rivaa, Daniele Pontirolia, Matteo Araminia, Mattia Gaboardia, Alessio Gaimarrib, Samuele Sannab, Chiara
Milanesec and Mauro Riccòa
a
Dipartimento di Fisica e Scienze della Terra, Università degli Studi di Parma, Parma, Italy
b
Dipartimento di Fisica, Università degli Studi di Pavia, Pavia, Italy
c
Dipartimento di Chimica-Fisica, Università degli Studi di Pavia, Italy
The employment of renewable sources for the production of energy also requires its storage in an even more efficient and safe way.
Recently, metal intercalated fullerides demonstrated to be quite interesting in the framework of energy storage, either as hydrogen
absorbers [1, 2], or as components of high-performance ion batteries [3, 4].
In particular, Li intercalates easily in C60 (up to 30 Li atoms per C60 molecule), thanks to the favourable C60 redox properties and the
small dimensions of Li+ ions. In LixC60 compounds, at low doping regime (x = 4), polymerization of the C60 units occurs and the
compound behaves as a superionic conductor [4], while at high doping level (x = 6, 12) fullerenes are in monomer form in a fcc
crystal arrangement. Starting from Li6C60 we managed to produce also the intercalated hydrofullerite Li6C60Hy (y = 36 ÷ 40), by
applying high H2 pressure at high temperature and in this case the crystal structure changes from fcc to bcc, depending on the
hydrogenation level.
DC/AC conductivity measurements and 7Li NMR spectroscopy indicated that, either in LixC60 (x = 6, 12) or in LixC60Hy (x = 6), Li+
ions are highly mobile already at room temperature, suggesting possible applications in the field of Li-ion batteries for these
compounds.
[1] J. Teprovich Jr., M. Wellons, et al, Nano Letters 2012, 2, 582 ; [2] P. Mauron, A. Remhof, et al., International Journal of Hydrogen Energy 2012,
19, 14307 ; [3] D. Pontiroli, M. Aramini, et al., Carbon 2013, 1, 143 ; [4] M. Riccò, M. Belli, et al., Phys. Rev. Lett. 2009, 14, 145901.
Synthesis of nickel decorated graphene and study of its interaction with hydrogen
Giacomo Magnania, Mattia Gaboardia, Giovanni Bertonib, Andreas Bliersbachc, Daniele Pontirolia, Matteo Araminia,
Georgia Vlachopouloua, Mauro Riccòa, Giancarlo Salviatib
a
Department of Physics and Earth Science, University of Parma, via G. Usberti 7/A, Parma, Italy
b
c
EMPA, Swiss Federal Laboratories for Materials Science and Technology, Division ‘‘Hydrogen and Energy’’,
Überlandstrasse 129, 8600 Dübendorf, Switzerland.
attached to graphene.
[1] M. Choucair et al., Nature nanotechnology 7 (2008) 1-4 ; [2] A.K. Singh et al., ACS Nano 3 (2009) 1657-1662.
Sythesis and structural characterization of Li12C60
Fabio Giglioa, Daniele Pontirolia, Mattia Gaboardia, Matteo Araminia, Chiara Cavallarib, Michela Brunellib, Mauro
Riccòa
a
Department of Physics and Earth Sciences, University of Parma, Via G. P. Usberti 7/a, 43124 Parma, Italy
b
Institut Laue Langevin, BP 156, 6, rue Jules Horowitz, 38042 Grenoble Cedex 9, France
49 Poster Session Functional nanostructures Carbon based materials are widely studied systems in the field of gas storage mainly for their light weight and high porosity. The
gram scale production of graphene [1] has expanded the interest in this material for these applications, due to its large effective
surface area (2630 m2/g). However, graphene has weak tendency toward adsorption of H2 and only at extreme conditions the fully
hydrogenated graphene (in which the hydrogen is strongly chemisorbed), can be obtained. A possibility to increase the interaction
between hydrogen and the carbon surface is the decoration of the latter with metal atoms, which promotes catalytic properties
towards H2 molecule dissociation and reversibility of atomic hydrogen binding to the graphene-receptor (spill-over effect) [2].
We developed a novel 2-steps method for the bulk synthesis of Ni nanoparticles decorated graphene (avoiding the exposition to air).
The morphological, magnetic, spectroscopic and hydrogen interaction properties of the samples were investigated by means of high
resolution transmission electron microscopy (HRTEM, HAADF-STEM), SQuID magnetometry, XPS, Raman and Muon Spin
Rotation (μSR) techniques. The formation of 5-17 nm (depending on the synthesis) super-paramagnetic monodispersed fcc-Ni NPs
decorating single layer graphenes (often folded) was observed. The size and the distribution of NPs can be optimized varying the
thermal rate and the concentration of metal precursor. Absorption measurements highlighted a 51% increased hydrogen adsorption
than in common carbon based materials. The μSR experiment showed a sizeable fraction of Muonium (light isotope of H)
In the last years carbon-based nanostructures are widely studied systems due to their promising properties in the fields of
superconductivity and energy storage. [1][2] One of the more challenging class concerns the intercalated compounds of the C60
fullerene with metals. Alkali metal intercalated fullerides are potential candidates as hydrogen storage materials due to the low
weight and enhanced hydrogen chemisorption at low temperature. [3]
As a π–rich system the C60 fullerene supports a charge transfer interaction which influences its electronic properties: it’s a matter of
fact that C60 can accommodate a high number of electrons donated by intercalated metal cations. Li12C60 is predicted theoretically to
form a so called superfulleroid showing a very high capacity to store hydrogen (13% wt). [4] It is still an unresolved question
whether it is possible or not to attain a superfulleroid arrangement in the solid state and the high stoichiometry intercalated fullerides
represent a relatively unexplored area. Usual synthetic approach based on azide method decomposition or on direct synthesis via
metal evaporation leads to issues for the lithium compounds case.
We investigated a new approach to produce lithium intercalated fulleride compounds with a definite stoichiometric control. The
synthesis method consist in a ball-milling technique in order to uniformly mixing the alkali metal with the fullerene powder and a
following thermal annealing to promote the solid-state reaction.
In this work synthesis and characterization of Li12C60 as a single polycrystallinic phase is reported. A crystallographic
characterization by powder neutron diffraction at low temperature was carried out. Simulated annealing calculations and Rietveld
refinement suggest the C60 structure, which usually exhibits a face-centered cubic cell, undergoes a symmetry loss related to the
intercalant clustering in the tetrahedral and octahedral interstices. This results in a distortion of the original C60 cubic cell and in a
two-layers alternate orientation for the C60 fullerenes (see Figure). Low symmetry constrains the structural description of the Li12C60
system to a P21/n cell.
[1] Iwasa Y., Takenobu T., Journal of Physics: Condensed Matter, vol. 15, no. 13, pp. R495–R519, Apr. 2003 ; [2] Riccò M., Belli M., et al., Physical
Review Letters, vol. 102, no. 14, p. 145901, Apr. 2009 ; [3] Mauron P., Remhof A., et al., International Journal of Hydrogen Energy, vol. 37, no. 19,
pp. 14307–14314, Oct. 2012 ; [4] Sun Q., Jena P., et al., Journal of the American Chemical Society, vol. 128, no. 30, pp. 9741–5, Aug. 2006.
Synthesis and characterization of the Mg2C60 ionic conductor
Poster Session Functional nanostructures Silvia Virdisa, Daniele Pontirolia, Matteo Araminia, Mattia Gaboardia, Fabio Orlandib, Lara Righib, Gianluca Calestanib
and Mauro Riccòa
a
Dipartimento di Fisica e Scienze della Terra, Università degli Studi di Parma, Parma, Italy
b
Dipartimento di Chimica, Università degli Studi di Parma, Parma, Italy
Fullerite C60 is known to easily reacts with atoms and molecules able to donate their electrons forming charge transfer salts. Alkali
and alkali-earth intercalated fullerides are a wide studied class of materials with applications in hydrogen storage[1] and as solid state
electrolytes [2,3]. Recently we managed to produce a new Mg intercalated fullerene crystal, namely Mg2C60, where C60 units
arrange in a quite unusual polymer structure, isostructural with the superionic compound Li4C60[4]. Mg2C60 displays relatively
high ionic conductivity, with the onset of Mg2+ diffusion observed already at 120 K,
following the ideal Debye model of diffusion. Rietveld refinement of X-ray diffraction
patterns reveal the formation of a monoclinic structure in which Mg2+ ions are holded in
the pseudo-tetrahedral voids. The charge transfer from the metal to the fullerene molecule
stabilizes a peculiar 2D polymeric structure in which different C60 molecules are
connected via sp3 hybridization of carbon and form planes through which Mg2+ ions can
diffuse [2]. In this work we investigate different types of solid state synthesis of MgxC60
using metallic magnesium and magnesium hydride (MgH2) as precursors. The synthesis
was carried out either by letting directly react Mg fine powder mixed to C60 in a closed
Ta tube at high temperature under vacuum, or by mixing MgH2 and C60 and thermally
decomposing the hydride under dynamic vacuum. In the former case, we were able also
to grow sufficiently large single-crystals of Mg2C60, which, to our knowledge, represent
a unique case in the framework of metal intercalated fullerene polymers. Physical vapour
phase deposition was besides investigated by making use of dendritic Mg and C60
powder. The structures were analysed by means of single crystal and powder XRD
technique and Pair Distribution Function (PDF) analysis.
[1] P. Mauron, et al., “Reversible hydrogen absorption in sodium intercalated fullerenes”, Int. J. Hydrogen Energy 2012, 37, 14307-14314 ; [2] D.
Pontiroli et al., “Ionic conductivity in Mg intercalated fullerene polymer Mg2C60”, Carbon 2012, 51, 143-147. [3] Orit Chusid et al., “Solid-State
Rechargeable Magnesium Batteries”, Adv. Mater. 2003, 15, 627-30 ; [4] M. Riccò, M. Belli, M. Mazzani, D. Pontiroli, D. Quintavalle, A. Jánossy
and G. Csányi, "Superionic conductivity in the Li4C60 fullerene polymer", Phys. Rev. Lett. 102, (2009), 45901.
Silylation route toward novel multifunctional (nano)composites
Margherita Dursoa, Tamara Posatib, Anna Sagnellaa, Valentina Benfenatia, Giampiero Ruanic, Vincenzo Palermoa,
Roberto Zambonia, Manuela Meluccia
50 a
ISOF-CNR, Bologna, Italy
Laboratory MIST E-R, Bologna, Italy
c
ISMN-CNR, Bologna, Italy
b
The development of new functional composites is a field of increasing interest for both academic and industrial purposes. In this
communication, we introduce the direct silylation as a chemical strategy to covalently modify selected nanomaterials. In particular,
three different substrates are considered and used as model platforms to check the valuability of the method and to realize new
fluorescent nanocomposites of potential interest in organic electronics as well as biomedicine and diagnostics:
i) inorganic hydrotalcite nanoparticles (HTlc-NPs), i.e. biocompatible layered double hydroxides characterized by positively charges
in their surface balanced with interlayer anions,[1] ii) silk fibroin (SF), natural biocompatible biomaterial extracted from Bombyx
mori cocoon,[2] and iii) graphene oxide (GO) nanosheets, two-dimensional nanostructures derived from exfoliation of graphite
oxide.[3] Such different materials have in common a huge presence of hydroxyl groups on their surfaces, that makes possible the
grafting of silylated -conjugated molecules to realize new fluorescent covalently-functionalized composites.[4]
We show that this method is a powerful chemical approach for the fine tuning of the chemo-physical surface properties of
(bio)materials, thus it represents a promising and easy tool to enhance their field of applications.
[1] Khan A.I., O'Hare D., J. Mater. Chem. 2002, 12, 3191 ; [2] Rockwood D.N., Preda R.C., Yücel T., Wang X., Lovett M. L., Kaplan D. L., Nat.
Protoc. 2011, 6, 1612 ; [3] Park S., Ruoff R. S., Nat. Nanotechnol. 2009, 4, 21 ; [4] Melucci M., Treossi E., Ortolani L., Giambastiani G., Morandi V.,
Klar P., Casiraghi C., Samorı` P., Palermo V., J. Mater. Chem. 2010, 20, 9052.
Hierarchical assembly of CuO nanostructures for photocatalytic application
Marco Villania, Aderemi Babatunde Alabib, Nicola Coppedèa, Laura Lazzarinia, Davide Calestania and Andrea
Zappettinia
a
b
Department of Physics, University of Ilorin, Ilorin, Nigeria
[1] Bao Q.L., Li C.M., Liao L., Yang H. B., Wang W., Ke C., Song Q. L., Bao H. F., Yu T., Loh K.P., Nanotechnology, 2009, 20, 065203 ; [2]
Anandan S., Wen X.G., Yang S.H., Mater. Chem. Phys., 2005, 93, 35 ; [3] Switzer J.A., Kothari H.M., Poizot P., Nakanishi S., Bohannan E.W.,
Nature, 2003, 425, 490 ; [4] Chowdhuri A., Gupta V., Sreenivas K., Kumar R., Mozumdar S., Patanjali P.K., Appl. Phys. Lett., 2004, 84, 118021 ; [5]
Zhang J.T., Liu J.F., Peng Q., Wang X., Li Y.D., Chem. Mater., 2006, 18, 867 ; [6] Lim Y.F., Choi J.J., Hanrath T., Journal of Nanomaterials, 2012,
1, 1 ; [7] Vaseem M., Umar A., Hahn Y.B., Kim D.H., Lee K.S., Jang J.S., Lee J. S., Catal. Commun., 2008, 10, 11 ; [8] Barreca D., Fornasiero P.,
Gasparotto A., Gombac V., Maccato C., Motini T., Tondello E., Chem Sus Chem, 2009, 2(3), 230 ; [9] Vaseem M., Umar A., Hahn Y.B., Kim D.H.,
Lee K.S., Jang J.S., Lee J.S., Catalysis Communications, 2008, 10, 11 ; [10] Liu J., Jin J., Deng Z., Huang S.Z., Hua Z.Y., Wang L., Wang C., Chen
L.H., Li Y., Van Tendeloo G., Su B., J. Colloid Interf. Sci., 2012, 384, 1
Ethanol gas sensing mechanism for ZnO nanowires
Kiptiemoi K. Korir a,b, G. Ciceroa,b and A. Catellanib,c1
a
Dipartimento scienze applicata e Tecnologia, Politecnico of Torino, Torino, Italy.
b
CNR-IMEM, Parco Area delle Scienze 37A, 1-431100 Parma, Italy
c
CNR-NANO, Istituto Nanoscienze, Centro S3 I-41125 Modena, Italy
51 Poster Session Functional nanostructures Semiconducting cuprous (Cu2O) and cupric oxide (CuO) has been widely investigated for technological application such as electrical
and photovoltaic devices [1,2], heterogeneous catalysis [3] and gas sensor [4,5].
In particular, copper (II) oxide is a p-type semiconductor with a narrow band gap and has gained attention as absorbing material in
light harvesting applications [6] such as excitonic solar cells and photocatalytic systems [7,8]. In either applicative fields to gain
control over dimensions, morphology and crystallinity is crucial: on the one hand in order to promote an efficient charge transfer
across the active heterojunction of the solar cell, on the other hand photocatalytic activity is highly dependent on the semiconductor
surface area and defect states concentration.
Herein we present a simple solution-based protocol to produce a highly efficient photocatalyst consisting of a 3D assembly of 2D
nanostructures via one-pot synthesis. Such hierarchical assembly allow a very high surface/volume ratio and facing of active
photocatalytic surface. Morphological and structural investigations of the as-grown CuO nanostructures have been performed by
FESEM, STEM, HRTEM, SAED and XRD analyses. A detailed study of the photocatalytic activity has been carried out, comparing
CuO with reference TiO2 nanoparticles: a very high photocatalytic activity has been measured, higher than that of commercial TiO2
and among the best reported in literature for CuO [9,10]. This can be tentatively ascribed to the synthetic procedure: on the one hand
the hierarchical assembly exhibit a very high surface to volume ratio; on the other, the surfactant-free approach allows the whole
surface of the nanostructure to be exposed to the chemical environment and hence maximize the photo-degradation of organic
pollutants.
Solid-state gas sensors play an important role in environmental monitoring, chemical process control, and personal safety. ZnO
nanowires are expected to offer better sensitivity to gas molecules due to their large surface area to volume ratio. A clear idea on the
gas sensing mechanism of this material is still lacking; yet its knowledge would possibly lead to the engineering of sensing elements
with enhanced sensitivities. In our work, we perform ab initio calculations based on the density functional theory (DFT) to show that
the ZnO sensing mechanism is based on the competitive adsorption at the surface of the device, that is between the oxygen molecules
present in the atmosphere and the gas to be detected. In particular, we show that, in the case of ethanol, its larger binding energy to
the ZnO surface if compared to O2, induces a switching in surface conductance i.e. between semiconducting and conducting that can
be detected electronically and related to the ethanol concentration.
Piezoelectric properties of zinc oxide nanowires: An ab-initio study
Kiptiemoi K. Korir a,b, G. Ciceroa,b and A. Catellanib,c
a
Dipartimento scienze applicata e Tecnologia, Politecnico of Torino, Torino, Italy
b
CNR-IMEM, Parco Area delle Scienze 37A, 1-431100 Parma, Italy
c
CNR-NANO, Istituto Nanoscienze, Centro S3 I-41125 Modena, Italy
Nanowires made of materials with non-centrosymmetric crystal structure are expected to be ideal building blocks for self-powered
nanodevices due to their piezoelectric properties, yet a controversial explanation on the effective operational mechanisms and size
effects still delay their real exploitation. To solve this controversy, we propose a methodology based on DFT calculations of the
response of nanostructures to external deformations that allows to distinguish between the different (bulk and surface) contributions:
we apply this scheme to evaluate the piezoelectric properties of ZnO [0001] nanowires, with a diameter up to 2.3 nm. Our results
reveal that, while surface and confinement effects are negligible, effective strain energies, thus the nanowire mechanical response,
are dependent on size. Our unified approach allows for a proper definition of piezoelectric coefficients for nanostructures, and
explains in a rigorous way the reason why nanowires are found to be more sensitive to mechanical deformation than the
corresponding bulk material.
Functionalization of SiC/SiO2 NWs with MNPs or porphyrins via ‘click’ chemistry
Poster Session Functional nanostructures Elena Bedognia, A. Secchia, M. Campaninib, L. Nasib, F. Rossib, V. Chiesib, F. Casolib, F. Albertinib, T. Rimoldib, L.
Cristofolinib, G. Attolinib, M. Negrib, G. Salviatib and F. Bigi a
a
Dipartimento di Chimica dell'Università,,Parma,Italy
b
In recent years, increasing attention has been devoting in the literature to the preparation of nanosystems for biomedical applications,
such as drug delivery, bio-separation, immunoassays, MRI contrast enhancement, and in particular for alternative approaches in
cancer treatment, such as photodynamic therapy and hyperthermia.
In this communication we report the preparation of two novel nanosystems obtained by functionalization of the core-shell SiC@SiO2
nanowires with magnetite nanoparticles or with porphyrins for application in nanomedicine, employing the same synthetic strategy.
Indeed, in both the cases the Huisgen 1,3-dipolar cycloaddition reaction (click-chemistry reaction) allowed to obtain their efficient
grafting to the nanowire surface. To this purpose azide groups were introduced on the surface of the silica shell of the NWs and C-C
triple bonds were introduced in the porphyrin structure or in the stabilizing agents of the magnetite nanoparticles. Magnetite (Fe3O4)
nanoparticles (MNPs) are suitable materials for hyperthermia, provided their size is carefully tailored (< 20 nm), to the applied
alternating magnetic field frequency. Due to its high biocompatibility, cubic SiC is a promising material for biomedical application
[1] and, in particular, theoretical studies predict cubic (100) SiC nanowires have
the highest thermal conductivity. This property can maximize and optimize the
heat distribution along the NWs and in turn inside the cancer cell. Moreover, the
NWs can easily penetrate the cell membrane remaining included inside.
Magnetite nanoparticles of 4 and 8 nm were obtained by thermal decomposition
of Fe(acac)3 in 1,2-hexadecandiol using oleic acid and oleylamine as stabilizers
at different temperature.[2] The black-brown mixture obtained was precipitated
with EtOH and dispersed in hexane, giving a colloidal solution. Then, 10undecynoic acid was added to introduce the alkyne groups. The MNPs were
well characterized using different techniques. Analysis of conventional TEM
images showed that the obtained samples consist of well stabilized nanoparticles
of nearly spherical shape, with homogeneous size distributions centered around
8 and 4 nm, respectively. The high resolution studies confirmed that the
N
N
N
nanoparticles are single crystalline. Electron diffraction from a large area of the Si
sample was used to analyze the MNP structure. The positions and the relative
intensity of diffraction rings match well with those typical of magnetite powder.
The nanoparticles show a superparamagnetic behavior at room temperature.
52 The MNP activity as hyperthermic agents has been tested by magnetic hyperthermia experiments. The nanowires were then
decorated with magnetite nanoparticles via click-chemistry reaction. The Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) is a
well known click reaction leading to the easy stereoselective formation of 1,4-substituted triazole. Thus, the reaction at room
temperature of the alkyne group on the MNPs and the azide on the NWs afforded the new nanosystem, where the nanowire was
covered by Fe3O4 MNPs through stable chemical bonds. The TEM analysis of the hybrid material obtained clearly demonstrated the
successful functionalization. Phorphyrins are an important class of photosensitizers largely employed in PDT and we decided to
conjugate porphyrins to the NWs. Also in this case the attachment of the photosensitizer to SiC/SiO2 nanowires was accomplished
on the basis of reactive group-matching. We selected to prepare variously substituted tetraarylporphyrins bearing at least one
carboxylic group. The carboxylic group was activated and reacted with propargylamine, affording the corresponding porphyrin with
an alkyne terminal group. In this case the azide-alkyne cycloaddition was carried out under termal conditions at 100 °C to avoid the
Cu metal insertion into the porphyrin core. The hybrid nanosystem was characterized by fluorescence spectroscopy, that confirmed
the successful porphyrin conjugation. Studies on the preparation of the three component nanosytem, SiC@SiO2 / MNP/porphyrin, are
in progress.
[1] Frewin C.L ., Jaroszeski M., et al., J. Mol. Recognit. 2009, 22, 380 ; [2] Sun S., Zeng H.,et al., J. Am. Chem. Soc. 2004, 126, 273.
Study of nanostructures based on SiC/SiO2 for the realization of a prototypal microdevice as subretinal implant:
Cytotoxicity tests
Paola Lagonegro1, F. Rossi1, G. Attolini1, M. Bosi1 , F. Boschi1, M. Negri1, T. Rimoldi2, L. Cristofolini2, R. Alinovi3,
S. Pinelli3, A. Mutti3 , C. Macaluso3 and G. Salviati1
1
IMEM-CNR, Parco Area delle Scienze 37/A 43124 Parma
2
Dipartimento di Fisica, Università di Parma, Parco Area delle Scienze 17/A, 43124 Parma
3
Dipartimento di Medicina Clinica e Sperimentale, Università di Parma, Via Gramsci, 14, 43126 Parma
53 Poster Session Functional nanostructures Nanowires (NWs) open promising near-future perspectives for the design and fabrication of nano-scale devices. NWs as
biocompatible nano-probes for biological systems. Also, due to its high biocompatibility, cubic SiC is a promising material for
biomedical applications and biomedical devices.
The retina is composed of brain tissue with cells (rods and cones) in the subretinal part that work as photoreceptors (Fig1). They
convert photons in signals, processed by the neural tissues (bipolar cells/ganglion/neuron) in the epiretinal part, then transmitted to
the brain. If photoreceptors are damaged, visual loss occurs but the neuronal circuitries for signal transmission are still efficient. The
stimulation of the neuronal tissues with electrical impulses originating from subretinal visual prosthesis, like electronic chips cellular
connections of retinal neurons implant.
The goal is to realize a subretinal implantable prototype based on a nano-on-micro technology developed on flexible polymers
(Fig1). The final device has overall micrometric dimensions, but with spatial resolution given by nanostructured photoreceptors and a
signal transmission based on charge accumulation mechanisms typical of inorganic MOS (metal-oxide-semiconductor) architecture.
The light is harvested by each single SiC nanowires while the impulse is transmitted to the neuronal network once a critical voltage
threshold is reached. Arrays of NWs are arranged on a flexible substrate. Here we propose the first step in biocompatibility
evaluation of biomedical devices, the cytotoxicity test, according to iso 10993-5. SiC/SiO2 core/shell NWs were grown by a
Chemical Vapour Deposition (CVD) process on n-type Si (001) substrate , using carbon monoxide (CO) as the carbon source and
iron nitrate as catalyst. The synthesis, performed at temperatures between 1050-1100°C in open-tube configuration, is based on the
carbothermal reduction of silica present as native oxide on the substrate surface, where the reaction is catalyzed by Fe. The NWs
have a diameter about 60 nm with a core (SiC) of approximately 20 nm(Fig 3). Nanowires were characterized by scanning electron
microscopy (SEM), High-Resolution transmission electron microscopy (HR-TEM) and High Angle Annular Dark Field imaging in
Scanning mode (HAADF-STEM).
Since the NWs surface isn’t a conventional substrate for cell seeding, it is important to examine the cytotoxicity separately from the
attachment of cells to the material. According to ISO 10993-5, the cells were seeded on substrate following direct method contact.
Fluorescence microscopy gave a qualitative evaluation of cells vitality and attachment, while quantitative measurement and
cytotoxicity were assessed through MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. For both
experiments SK-N-MC neuroepithelioma cell line (ATCC, Rockville, MD,USA) and A549 cells are adenocarcinomic human
alveolar basal epithelial cell line were used. We seeded 10^5 cells/ml on NWs core-shell samples of 1x1 cm. SK-NMC and A549
cells were cultured in Dulbecco's Modified Eagle Medium (DMEM). Plates were maintained at 37°C and 5% CO2 in a humidified
atmosphere for 24h and 48h. After 24h and 48h all samples were washed with abundant DMEM and phosphate buffer solution
(PBS). Some cultures were marked with calcein, a fluorescent dye with an excitation and emission wavelengths of 495/515 nm, and
after 30 min fluorescence microscopy observations were performed (Fig 2) .Others underwent enzymatic process with trypsin and
the cells vitality was measured with MTT assay. Both tests show that cells adhere on substrate after 24 h, while growth and
multiplication are observed after 48h, thus opening promising near-future perspectives on biocompatibility studies of core-shell
nanowires.
ig.1. The eye structure, with section of the retina (top left). MD
scheme, with indication of different materials and coating layers
(bottom). SiC/SiO2 NW TEM cross section, sketching the Au
external layer mimicking the MOS NW (top right).
ZnO nanotetrapods as advanced tools for nanomedicine and water remediation
Poster Session Functional nanostructures Marco Villania, Davide Calestania, Nicola Coppedèa, Laura Lazzarinia, Francesca Casolia, Valentina Chiesia, Franca
Albertinia, Tiziano Rimoldib, Nicola Castagnettib, and Andrea Zappettinia
a
b
Dipartimento di Fisica, Università degli Studi di Parma
Zinc oxide tetrapods (ZnO TP) gain more and more attention in material science as their exotic morphology is combined with a large
number of application fields (optoelectronic, photovoltaic, gas- and biosensing, nanomedicine, photocatalysis, etc.). This versatility
can be further expanded through the tailoring of material properties by surface functionalization with different materials including
semiconductors, magnetic materials and noble metal nanoparticles. Two meaningful ZnO TP functionalization are herein reported,
using gold (Au) and magnetite (Fe3O4) nanoparticles. On the one hand, coupling with Au nanoparticles results in an advanced tool in
biological applications ranging from detection of pathogens, detection of proteins, probing of DNA structure, tissue engineering,
separation and purification of biological molecules and cells, enhancement of MRI contrast [1,2]. Taking advance of the metal
plasmon, SERS (Surface Enhanced Raman Spectroscopy) analysis can be performed using ZnO TP as a carrier, supporting Au
nanoparticles, thus avoiding the internalization of the biosensor inside the cellular environment. On the other hand, ZnO TP surface
has been decorated with Fe3O4 nanoparticles creating a multifunctional material which retains the attractive features of ZnO (e.g.
surface reactivity, strong UV emission, piezoelectricity) together with added magnetism [3]. Structural, morphological, optical,
magnetic and functional characterization are performed. In particular, the high saturation magnetization of Fe3O4 NP (above 50 A m2
kg-1), the strong UV luminescence and the enhanced photocatalytic activity of coupled nanostructures are discussed. Thus the
nanocomposite turns out to be suitable for applications in energy harvesting and conversion, gas- and bio-sensing, bio-medicine and
filter-free photocatalysis.
[1] Y. Wei, Y. Li, X. Liu, Y. Xian, G. Shi, L. Jin, Biosens. Bioelectron., 2010, 26, 275 ; [2] Y. Liu, M. Zhong, G. Shan, Y. Li, B. Huang, G. Yang, J.
Phys. Chem. B, 2008, 112, 6484 ; [3] M. Villani, T. Rimoldi, D. Calestani, L. Lazzarini, V. Chiesi, F. Casoli, F. Albertini, A. Zappettini,
Nanotechnology, 2013, 24, 135601
Properties of ZnO nanorods grown by hydrothermal synthesis on conductive layers
L.V. Podrezovaa, V. Caudab, S. Stassib,c, Giancarlo Ciceroc, Kh.A. Abdullind, B.E. Alpysbaevad
a
Det. of General and Theoretical Physics, Kazakh National Technical Univ., 050013, Almaty, Kazakhstan.
b
Center for Space Human Robotics, Istituto Italiano di Tecnologia, Corso Trento 21, 10129 Turin, Italy.
c
Dept. of Applied Science and Technology, Politecnico di Torino, Corso Duca degli Abruzzi, 24, 10129 Turin, Italy
d
National Nanotec Open Lab., Kazakh National University, 71 Al-Farabi Ave., Аlmaty, 050000, Republic of Kazakhstan
Zinc oxide nanorods (ZnO NRs), grown in water solution [1-2], were obtained on the different substrates covered by conductive
materials, deposited as a bottom layers. The influence of different metal layers, such as Cu, Ni, Pt, Ag,Au, sputtered on silicon
substrates and F-doped SnO2 (FTO) coated-glass wafers on the properties of the synthesized ZnO nanorods were investidated. The
samples were studied by scanning electron microscopy, X-ray diffraction, atomic force microscopy, current - voltage (I – V)
measurements and photoluminescence. We obtained vertically aligned ZnO nanorod arrays on all the used substrates, proving how
ease and reproducible is the growth of ZnO nanorods on different metal layers. Depending on the deposited conductive material as
bottom layer, we obtained different morphologies, optical and electrical features. The obtained ZnO NRs on conductive layers are
promising for several applications, including opto-electronic and gas sensing nanodevice applications.
54 [1] Chin-Hsien Hung, Wha-Tzong Whang, Materials Chemistry and Physics, 82, 2003, pp. 705–710 ; [2] Zhong Lin Wang, Materials Science and
Engineering R, 64, 2009, pp. 33–71.
Deposition via spray deposition of Cu2S efficient counter electrodes for quantum dot sensitized solar cells
Isabella Concina
SENSOR Lab CNR INO, Brescia, Italy
SENSOR Lab, University of Brescia, Brescia, Italy
Although quantum dot sensitized solar cells (QDSSCs) are very promising devices in the field of solar energy conversion [1], there
still are open issues limiting the systematic fabrication of performant devices. Among them, the lack of reproducible, stable and
efficient counter electrodes (CEs) is particularly troublesome. Herein, we present the preparation of copper sulphide CEs by spray
deposition [3] to be applied as cathodes in QDSSCs. Spray deposition of Cu(NO3)2 x 3 H2O and CS(NH2)2 resulted in homogeneous
amorphous nanosized thin film and subsequent reaction with polysulfide electrolyte delivers Cu2S hierarchical structures, suitable to
be applied as CEs. Proposed procedure is very fast as compared with currently adopted strategies (such for instance treatment of
brass foils/wires), straightforward, being able to produce several CEs at once, and highly reproducible. Cu2S hierarchical CEs were
applied as cathodes in QDSSCs [4],[5], whose sensitization layer consisted of SILAR-deposited semiconductor quantum dots, in
particular CdS, PbS, CdS/PbS, CdS/CdSe, PbS/CdS/CdSe. For each applied sensitization system, excellent performances were
recorded, especially related to improved photocurrent densities (higher than 15 mA/cm2) and fill factors, this latter testifying the good
catalytic activity of the spray-deposited CE. Photoconversion efficiencies as high as 2.98% and 3.75%, with associated incident
photo-to-current efficiencies of 80% and 90%, were obtained with mixed networks of PbS/CdS and CdS/CdSe, respectively.
[1] Rühle, S.; Shalom, M.; Zaban, A. Quantum-Dot-Sensitized Solar Cells. Chem. Phys. Chem. 2010, 11, 2290-2304 ; [2] Lee, Y.-L.; Lo, Y.-S.
Highly Efficient Quantum-Dot-Sensitized Solar Cell Based on Co-Sensitization of CdS/CdSe. Adv. Func. Mat. 2009, 19, 604-609 ; [3] Lee, H.;
Wang, M.; Chen, P.; Gamelin, D.R.; Zakeeruddin, S.M.; Gratzel, M.; Nazeeruddin Md K., Efficient CdSe Quantum Dot-Sensitized Solar Cells
Prepared by an Improved Successive Ionic Layer Adsorption and Reaction Process. Nano Lett. 2009, 9, 4221-4227.
Scale-up of an electrochemical anodization process for the production of nanostructured WO3 photoanodes
Giuseppe M. Guadalupia, Marcello Marellaa, Marco Guidolina, Fabio Gerolina, Marino Battagliarina, Laura Medab,
Alessandra Taccab, Fabio Oldani
a
Venezia Tecnologie S.p.A, Porto Marghera, Italy
b
Istituto ENI-Donegani, Novara, Italy
55 Poster Session Functional nanostructures Semiconductor metal oxides are nowadays attractive materials to be employed as photoanodes in photoelectrochemical (PEC)
devices. The most important applications are i) water splitting for the production of H2 and O2, ii) waste treatment through the
photodegradation of organic pollutants with simultaneous H2 evolution. Tungsten trioxide is an interesting material since it is stable
under acidic conditions (pH < 4) and helds an appropriate indirect band gap (Eg ≈ 2.6 eV) to absorb the visible light up to ca. 470
nm. Furthermore, the relatively high absorption depth (≈ 10 μm) and the nanostructured morphology allow to avoid the
recombination processes. Among the methodologies for the preparation of nanostructured WO3, the electrochemical anodization of
tungsten sheets is one of the most versatile in terms of process scalability. Aim of this work is the scale-up of a proprietary
electrochemical anodization process for the preparation of nanostructured and crystalline WO3 photoanodes with photocatalytic
activity towards water oxidation.

ICG2013 - Final Program, List of Abstracts and - Imem-Cnr

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