HEAD: Dr. MIHAIL FLORIN LAZARESCU E

Transcription

NATIONAL INSTITUTE OF MATERIALS PHYSICS* ANNUAL REPORT 2005
Laboratory of Advanced Materials for Special Applications
HEAD: Dr. MIHAIL FLORIN LAZARESCU
E-mail: [email protected]
Tel : (+4021) 493 01 95
Fax :(+4021) 493 02 67
TOTAL EMPLOYEES: 20
A. GROUP OF CRYSTAL GROWTH AND CRYSTAL CHARACTERIZATION
HEAD: Dr. MIHAIL FLORIN LAZARESCU
Tel : (+4021) 493 01 95
Fax :(+4021) 493 02 67
RESEARCH TEAM : 9
1. Dr. Mihail Florin LAZARESCU
2. Dr. Adrian Stefan MANEA
3. Dr. Constantin LOGOFATU
4. Dr. Marin CERNEA
5. Dr. Rodica GHITA
6. Constantin COTARLAN
7. Drd. Constantin NEGRILA
8. Drd. Florica UNGUREANU
9. Doina RADULESCU
senior researcher II
senior researcher III
assistant researcher
engineer
B. GROUP OF PHYSICS OF HIGH FREQUENCY MATERIALS AND DEVICES
HEAD: Dr. ANDREI IOACHIM
Tel: (+4021) 493 01 95
Fax: (+4021) 493 02 67
RESEARCH TEAM: 7
1. Dr. Andrei IOACHIM
2. Dr. Marian Gabriel BANCIU
3. Ph.D.cand. Liviu NEDELCU
4. Dragos GHETU
5. Constantin Augustin DUTU
6. Marian IOSIF
7. Alexandru GAVRILA
researcher
engineer
engineer
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PRESENT RESEARCH INTERESTS:
1. Characterization of surface oxide states on GaAs and other semiconductor intermetallic
compounds by XPS technique;
2. The application of the sol-gel and magnetron plasma deposition methods in the field of
nanometric thin films preparation for the obtaining of semiconductor/semiconductor structures or
based on piezomaterials;
3. Development of a competitive technique for obtaining Schottky barriers devices on semiinsulating GaAs devoted to the fabrication of radiation sensors;
4. Techniques and methods for the synthesis of highly homogeneous magnetic alloys containing a
volatile component (e.g. Magnesium) in “extreme” conditions (under high pressure of inert pure
gases);
5. Development of bulk and thin-film materials with high dielectric constant and low loss in
microwave and millimetre wave range (ZST, BZT);
6. Research on BST ferroelectric materials for electrically controlled microwave devices;
7. Miniaturized temperature-stable devices by using ZST dielectric materials;
8. Investigations on new type of compact planar devices for mobile communications;
MAIN SCIENTIFIC RESULTS OBTAINED IN 2005:
1. Optimization of the technical procedure for the obtaining of Schottky structures based on SIGaAs
An “in situ” procedure has been developed for the obtaining of insulating GaAs-based structures
devoted to the X-Ray detection at the room temperature. The methods of plasma etching cleaning of
surface, and the ohmic and non ohmic (Schottky) metallic contacts deposition by thermal
evaporation were used in this aim.
2. Microwave parameters optimization of ferroelectric solid solutions (Ba,Sr)TiO3 doped with MgO
and MnO2
The investigations on (Ba1−xSrx)TiO3 prepared by solid state reactions shown that the addition of
MgO and MnO2 improved the sintering process and decreased the dielectric loss. The grains exhibit
a cubical shape with dimensions in the 3-4 m range. The materials exhibit a dielectric constant εr
in the 200 ÷ 1000 range and loss tan between 10-3 to 10-2 at microwave frequencies.
3. Low loss Ba(Zn1/3Ta2/3)O3 for millimetre wave and microwave applications
Ba(Zn1/3Ta2/3)O3 ceramics with low loss in microwave domain were obtained by solid state reaction.
The investigations on dielectric properties revealed that the increase of sintering temperature
decrease the dielectric loss especially when an annealing of 10h at 14000C is performed. Qxf product
strongly depends on the BZT crystalline structure parameters, especially the unit cell distortion and
cationic order. Dielectric loss decreases with the increase of ordering degree in the structure and
with the disappearance of secondary phases. Lowest loss is obtained for a Zn and Ta completely
ordered BZT ceramic with a strongly distorted unit cell. Porosity has small effect on dielectric loss
of BZT material. Well-sintered and annealed BZT samples exhibit a dielectric constant around 31
and a Q x f product up to 130.000. Super-high quality factor of BZT materials
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recommends them for microwave and millimetre wave applications as resonators and filters for
wireless communication systems.
4. Microwave devices made of ZST materials
Band-pass filters with dielectric resonators of Ni-doped (Zr0.8, Sn0.2)TiO4 ceramic materials were
developed for X-band applications. The external coupling was performed using microstrip lines on a
substrate of 9.22 dielectric constant and 0.635 mm height. Filters with minimum insertion loss
between 0.46 dB and 1.74 dB, the bandwidth between 40 MHz and 170 MHz and with the central
frequency around 10 GHz were manufactured. Moreover, the resonance frequency temperature
coefficient τf , which takes values in the range –4 to +4ppm/oC offers a very good thermal stability to
the filters.
5. Size-reduced planar devices with improved characteristics for Universal Mobile Telecommunication Systems (UMTS)
Devices with modified stepped –impedance resonators were developed for UMTS base-stations. The
cross-couplings between resonators provide a quasi-elliptic frequency response for an improved
selectivity. The developed devices are cost-effective and offer an easy integration with low noise
amplifiers and other devices of the front-end circuits. The absence of the via-holes and of the
additional lumped components makes the proposed designs attractive for HTS devices and for
devices on high dielectric constant substrates.
INTERNATIONAL COOPERATIONS:
Project title: New RF and microwave devices, Partner: University of New South Wales, Sydney,
Australia
PAPERS PUBLISHED OR ACCEPTED FOR PUBLICATION IN 2005
1.V.Lazarescu, R.Scurtu, M.F.Lazarescu, E.Santos, H.Jones, W.Schmickler, “Field effects and
surface states in SHG at n-GaAs (hkl) electrodes”, Electrochimica Acta, 50, p.4830-4836, 2005
2.R.Ghita, C.Logofatu, C.Negrila, A.S.Manea, M.Cernea, M.F.Lazarescu, “Studies of ohmic
contact and Schottky barriers on Au-Ge/GaAs and Au-Ti/GaAs”, J.Optoelectronics and
Adv.Materials, 7(6), p.3033-3037, 2005
3.V.Lazarescu, M.Gartner, R.Scurtu, M.Anastasescu, A.Ghita, M.F.Lazarescu, W.Schmickler,
“Fermi level pinning at n-GaAs(110) electrodes "in“ passivation of metals and semiconductors and
properties of thin oxide layers", Eds.P.Marcuse and V. Maurice, Elsevier, 2006
4.C.Logofatu, C.Negrila, R.Ghita, F.Ungureanu, A.S.Manea, M.F.Lazarescu, “XPS study on
surface native oxides”, Revista de Tehnologii Neconventionale, Nr.4, p.31-34, 2005
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5.M.Braic, V.Braic, M.Balaceanu, G.Pavelescu, A.Vladescu, I.Tudor, A.Popescu, Z.Borsos,
C.Logofatu, C.Negrila, “Microchemical and mechanical characteristics of arc plasma deposited
TiAlN and TiN/TiAlN coatings”, J.Optoelectron.Adv. Mater, vol. 7, No. 2, p. 671-676, April. 2005
6.A.Ioachim, M.G.Banciu, M.I.Toacsen, L.Nedelcu, D.Ghetu, H.V.Alexandru, G.Stoica,
G.Annino, M.Cassettari, M.Martinelli, “Nickel-doped (Zr0.8, Sn0.2)TiO4 for microwave and
millimeter wave applications”, Materials Science and Engineering B, vol. 118, p. 205-209, 2005
7.H.V.Alexandru, C.Berbecaru, F.Stanculescu, A.Ioachim, M.G.Banciu, M.I.Toacsan, L.Nedelcu,
D.Ghetu, G.Stoica, “Ferroelectric solid solutions (Ba,Sr)TiO3 for microwave applications”,
Materials Science and Engineering B, vol. 118, p. 92-96, 2005
8.M.Nistor, F.Gherendi, M.Magureanu, N.B.Mandache, A.Ioachim, M.G.Banciu, L.Nedelcu,
M.Popescu, F.Sava, H.V.Alexandru, “(Zr, Sn)TiO4 thin films for applications in electronics”,
Applied Surface Science, vol. 247, p. 169-174, 2005
9.A.Ioachim, M.G.Banciu, L.Nedelcu, “Microwave dielectric properties of doped Ba0.5Sr0.5TiO3
ceramics correlated with sintering temperature”, J.Optoelectron.Adv. Mater, vol. 7, p. 3023-3027,
2005
10.M.G.Banciu, G.Lojewski, A.Ioachim, N.Militaru, L.Nedelcu, D.Brinaru, D.Ghetu, T.Petrescu,
”Compact filter design using wavelet processing of the FDTD signal”, Rom. Journ. Phys., vol. 50,
Nos. 9-10, p. 983-988, 2005
11.A.Ioachim, M.G.Banciu, M.I.Toacsen, L.Nedelcu, D.Ghetu, H.V.Alexandru, C.Berbecaru,
A.Dutu, G. Stoica, “High-K Mg-doped ZST for microwave applications”, accepted for publication
in Applied Surface Science
12.A.Ioachim, H.V.Alexandru, C.Berbecaru, S.Antohe, F.Stanculescu, M.G.Banciu, M.I.Toacsen,
L.Nedelcu, D.Ghetu, C.A.Dutu, G.Stoica, “Dopant Influence on BST Ferrolectric Solid Solutions
Family”, accepted for publication in Materials Science and Engineering C
13.H.V.Alexandru, C.Berbecaru, A.Ioachim, L.Nedelcu, C.A.Dutu, “BST Solid Solutions,
Temperature evolution of the Ferroelectric Transitions”, accepted for publication in Applied
Surface Science
14.M.G.Banciu, A.Ioachim, "Design of microwave devices by using artificial neural network
models", accepted for publication in Romanian Journal of Information Science and Technology.
15.N.Militaru, T.Petrescu, G.Lojewski, M.G.Banciu, A.Ioachim, “The effects of second oprder
cross-couplings in some compact microwave planar band-pass filters”, accepted for publication in
Rev. Roum. Sci. Tech. – Électrotechnique et Energie
16.M.G.Banciu, A.Ioachim, L.Nedelcu, D.Ghetu, G.Lojewski, N.Militaru, D.Brinaru, “Small-size
devices with improved characteristics for mobile communications”, Nonconventional Technologies
Review, No3, p. 79-84, 2005
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17.S.Shen, R.Ramer, MG.Banciu, R.R.Mansour, “Design and realization of star-geometry dualmode bandpass filter”,Optics Express, vol. 13, no. 24, p. 9753-9757, 2005
18.A.Ioachim, M.G.Banciu, M.I.Toacsan, L.Nedelcu, C.A.Dutu, I.Radu, I.Nicolaescu,
“Development of X-band filter with ZST dielectric resonators”, accepted for publication in
Romanian Journal of Information Science and Technology
19.A.Ioachim, M.I.Toacsan, M.G.Banciu, L.Nedelcu, D.Ghetu, C.A.Dutu, F.Vasiliu,
H.V.Alexandru, C.Berbecaru, G.Stoica, P.Nita, “Ferroelectric Ba1-xSrxTiO3 Materials for
Electrically Controlled Microwave Devices”, accepted for publication in Romanian Journal of
Information Science and Technology
CONFERENCES
1.V.Lazarescu, M.Gartner, R.Scurtu, M.Anastasescu, A.Ghita, M.F.Lazarescu, “Fermi level
pinning at n-GaAs(110) electrodes” Conf. Passivity 9, Paris- France, July 2005
2.R.Ghita, C.Logofatu, C.Negrila, A.S.Manea, M.Cernea, V.Ciupina, M.F.Lazarescu, “Aspects
of XPS study on Ti/oxidized GaAs interface”, 6-th International Balkan Workshop on Applied
Physics, July 5-7 2005, Constanta, Romania, Proceedings Abstracts p.79
3.R.Ghita, C.Logofatu, C.Negrila, A.S.Manea, M.Cernea, M.F.Lazarescu, “Studies of ohmic
contact and Schottky barriers on Au-Ge/GaAs and Au-Ti/GaAs”, !4-th National Conference on
Physics, September 13-17, Bucharest, Romania, Proceeedings Abstracts, p.66
4.M.Cernea, M.F.Lazarescu, A.S.Manea, C.Negrila, R.Ghita, G.Ioncea, E.Vasile, R.Trusca,
“Temperature influence on the processes which transform the sol-gel precursor of doped BaTiO3 in
dielectric material” The fourth International Conference on Science, Technology and Applications
of Sintering (SINTERING 05), Grenoble, France, August 29th - September 1st, 2005. Proceeding,
515-517, 2005
5.C.Logofatu, C.Negrila, R.Ghita, F.Ungureanu, A.S.Manea, M.F.Lazarescu, “XPS study on
surface native oxides”, ICNcT 2005-The 12-th International Conference of Nonconventional
Technologies, November 3-4, Bucharest, 2005
6.E.Dimitriu, F.Craciun, M.Cernea, R.Ramer, ”Effect of PZT compositions on dielectric and
piezoelectric properties”, Symposium “Materiais 2005”, Aveiro, Portugal, March 2005
7.A.L.Costa, G.Montanari, S.Albonetti, C.Galassi, M.Cernea, “Nanostructured Nb doped PZT
powders via sol-gel auto-combustion”, IX Conference & Exhibition of the European Ceramic
Society-ECERS, Portorož, Slovenia, 19 - 23 June, 2005
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8.M.G.Banciu, G.Lojewski, A.Ioachim, N.Militaru, L.Nedelcu, D.Ghetu, “Miniaturized planar
cross-coupled filters for UMTS application”, Proceeding of the 36 th International Scientific
Symposium of the Military Equipment and Technologies Research Agency, Bucuresti, Romania, 2627 mai 2005, vol. I, p. 522-527, 2005
9.A.Ioachim, M.I.Toacsan, M.G.Banciu, L.Nedelcu, F.Vasiliu, D.Ghetu, C.A.Dutu, F.Lifei,
H.V.Alexandru, C.Berbecaru, G.Stoica, P.Nita, “BST Ferroelectric Materials for Tunable
Microwave Devices”, Proceeding of the 36 th International Scientific Symposium of the Military
Equipment and Technologies Research Agency, Bucuresti, Romania, 26-27 mai 2005, vol. I, p. 528531, 2005
10.A.Ioachim, H.V.Alexandru, C.Berbecaru, S.Antohe, F.Stanculescu, M.G.Banciu, M.I.Toacsen,
L.Nedelcu, D.Ghetu, C.A.Dutu, G.Stoica, “Dopant influence on BST ferroelectric solid solutions
family”, E-MRS 2005 Spring Meeting, Strasbourg, France
11.A.Ioachim, M.G.Banciu, M.I.Toacsen, L.Nedelcu, D.Ghetu, H.V.Alexandru, C.Berbecaru, A.
Dutu, G.Stoica, “High-K Mg-doped ZST for microwave applications”, E-MRS 2005 Spring
Meeting, Strasbourg, France
12.H.V.Alexandru, C.Berbecaru, A.Ioachim, C.A.Dutu, “BST solid solutions, temperature
evolution of the ferroelectric transitions”, E-MRS 2005 Spring Meeting, Strasbourg, France
13.M.Nistor, A.Brunet-Bruneau, L.Siozade, B.Gallas, J.Perriere, W.Seiler, A.Ioachim, “Properties
of pulsed laser deposited ZrSnTiO thin films”, E-MRS 2005 Spring Meeting, Strasbourg, France
14.L.Nedelcu, A.Ioachim, M.G.Banciu, M.I.Toacsan, D.Ghetu, G.Stoica, G.Annino, M.Cassettari,
M.Martinelli, “Dielectric properties of Ni and Mg doped ZST ceramics for microwave and
millimeter wave applications”, IX Conference & Exhibition of the European Ceramic Society,
ECERS 2005, Portoroz, Slovenia
15.A.Ioachim, M.I.Toacsan, M.G.Banciu, L.Nedelcu, D.Ghetu, H.V.Alexandru, C.Berbecaru,
F.Vasiliu, P.Nita, R.Ramer, “Ferroelectric ceramics based on the BaO–SrO–TiO2 ternary system for
microwave applications”, IX Conference & Exhibition of the European Ceramic Society, ECERS
2005, Portoroz, Slovenia
16.A.Ioachim, M.I.Toacsan, M.G.Banciu, L.Nedelcu, D.Ghetu, M.Feder, C.Plapceanu, C.Ghica,
F.Lifei, P.Nita, “Effect of the sintering temperature on the Ba(Zn1/3Ta2/3)O3 - dielectric properties”,
IX Conference & Exhibition of the European Ceramic Society, ECERS 2005, Portoroz, Slovenia
17.A.Ioachim, “High-K ceramics and thin layers for microwave and millimeter wave devices”, The
6 th International Balcan Workshop on Applied Physics, Constanta, Romania, 2005
18.M.G.Banciu, “Development of compact cross-coupled Filters for Mobile Communications”, The
6 th International Balcan Workshop on Applied Physics, Constanta, Romania, 2005
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19.A.Ioachim, M.G.Banciu, L.Nedelcu, C.A.Dutu, “Filters with dielectric resonators of
(Zr0.8, Sn0.2) TiO4 materials”, The 6 th International Balcan Workshop on Applied Physics,
Constanta, Romania, 2005
20.H.VAlexandru, S.Antohe, C.Berbecaru, A.Ioachim, C.A.Dutu, V.Ciupina, R.C.Radulescu
“Peculiar ferroelectric transitions in barium strontium titanate versus composition”, The 6 th
International Balcan Workshop on Applied Physics, Constanta, Romania, 2005
21.MI.Toacsan, A.Ioachim, L.Nedelcu, H.V.Alexandru, “Accelerate ageing of PZT-type
ceramics”, International Conference on Perovskites – Properties and Potential Applications,
Dubendorf, Elvetia, 2005
22.A.Ioachim, M.I.Toacsan, M.G.Banciu, L.Nedelcu, D.Ghetu, F.Vasiliu, H.V.Alexandru,
C.Berbecaru, G.Stoica, P.Nita, “Barium Strontium Titanate - Based Perovskite Materials for
Microwave Applications”, International Conference on Perovskites – Properties and Potential
Applications, Dubendorf, Elvetia, 2005
23.A.Ioachim, M.G.Banciu, M.I.Toacsan, L.Nedelcu, C.A.Dutu, I.Radu, I.Nicolaescu, “X-band
filters manufactured with ZST dielectric resonators”, Proceedings of the 28 th International
Semiconductor Conference, CAS 2005, Sinaia, Romania, vol. 1, p. 99-102, 2005
24.M.G.Banciu, A.Ioachim, “A neural network approach to the design of the high frequency
devices”, Proceedings of the 28 th International Semiconductor Conference, CAS 2005, Sinaia,
Romania, vol. 1, p. 115-118, 2005
25.A.Ioachim, M.I.Toacsan, M.G.Banciu, L.Nedelcu, D.Ghetu, C.A.Dutu, F.Vasiliu,
H.V.Alexandru, C.Berbecaru, G.Stoica, P.Nita, “Ba1-xSrxTiO3 ceramics for tunable microwave
Romania, Vol. 2, p. 277-280, 2005
26.A.Ioachim, M.I.Toacsăn, M.G.Banciu, L.Nedelcu, H.V.Alexandru, G.Stoica, “Ferroelctric
ceramics based on the BaO – Nd2O3 –TiO2 ternary system for high frequency applications”,
International Conference on Fundamental and Applied Research in Physics, Iasi, Romania, 2005
27.A.Ioachim, M.G.Banciu, L.Nedelcu, C.A.Dutu, “Band-pass filters with (Zr0.8, Sn0.2) TiO4
dielectric resonators”, International Conference on Fundamental and Applied Research in Physics,
Iasi, Romania, 2005
PATENTS
1. Lazarescu Mihail Florin, Ghita Rodica, Manea Stefan Adrian, Logofatu Constantin, Negrila
Constantin Catalin, Ungureanu Florica, “Tight electrochemical cell for optical measurements at
solid-liquid interfaces”, Registred request: A/00827 from 30.09.2005
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Laboratory of Low Temperature Physics and Superconductivity
_____________________________________________________________________________
HEAD: Dr. LUCICA MIU
Tel.: (+4021) 493 01 95
Fax: (+4021) 493 02 67
TOTAL EMPLOYEES: 11
RESEARCH TEAM: 10
1. Dr. Lucica MIU
2. Dr. Mihai VELTER-STEFANESCU
3. Dr. Gheorghe Virgil ALDICA
4. Dr. Viorel Constantin SANDU*
5. Dr. Stelian POPA
6. Dr. Adrian Ioan CRISAN
7. Dr. Petre BADICA**
8. Dr. Valentina MIHALACHE
9. Monica Maria POPA
10. Oana Genoveva DEDIU***
senior researcher I
senior researcher I
senior researcher I
senior researcher I
senior researcher I
senior researcher I
researcher
chemist
Present address:
*
Kent State University, Kent, Ohio, USA
**
IMR, Tohoku University, Sendai, Japan
***
University of Heidelberg, Germany
PRESENT RESEARCH INTEREST:
Superconducting materials
Vortex structures, Vortex dynamics
1. Superconductivity in Li2B(Pd1-xPtx)3
A new pseudo-binary complete solid solution Li2B(Pd1-xPtx)3, x = 0-1, has been synthesized and
superconductivity in the entire x-range was reported [P.Badica, T.Kondo, K.Togano, J. Phys.
Soc. Jap. 74 (3), 1014, 2005]. Our results strongly suggest that superconductivity is of bulk type.
The critical temperature decreases approximately linearly with the amount of Pt, from 7.2-8 K
for Li2BPd3 to 2.2-2.8 K for Li2BPt3. For x = 0-1 a weak fishtail effect on the isothermal
magnetization curves was observed at low and intermediate fields.
2. Anisotropic vortex channeling in YBa2Cu3O7-δ thin films with ordered antidot arrays
Scanning Hall probe microscopy has been used to make a microscopic study of flux structures
and dynamics in YBCO thin-film disks containing a regular 10- µm-period square array of 2.5µm-sized holes (antidots) [A.Crisan, A.Pross, D.Cole, S.J.Bending, R.Wördenweber, P.Lahl,
E.H.Brandt, Phys. Rev. B 71, 144504, 2005]. Images obtained after field cooling the sample to
77 K in very low fields reveal that the holes can trap two flux quanta at this temperature. Scans
obtained after zero-field cooling (ZFC) to 77 K and a subsequent applied field cycle clearly
display preferential flux channeling along chains of antidots in the direction of maximum
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induction gradient. Remarkably, upon reversal of field sweep direction, we observe flux
“streaming” out of the holes towards the sample edges with almost uniform density flux “stripes”
bridging the holes in the exit direction. We estimate that the antidots can preferentially trap about
15 flux quanta in these ZFC experiments. Classical electrodynamics simulations appear to be in
good qualitative agreement with our results, indicating that many of the observed phenomena
may be geometrical effects that depend primarily on the shape and topology of the sample, and
potential applications are discussed.
3. Ordering of the creeping vortex system in in Bi2Sr2CaCu2O8+δ single crystals at low
temperatures
Zero-field-cooling magnetization relaxation measurements performed on Bi2Sr2CaCu2O8+δ single
crystals in the low-temperature domain, with the external magnetic field oriented parallelly to the
c axis, reveal the ordering of the creeping vortex system due to the macroscopic currents induced
in the sample [L.Miu, Phys. Rev. B 72, 132502, 2005, paper selected for the APS Virtual
Journal of Applications of Superconductivity, Vol. 9, Issue 9, November 1, 2005]. This explains
many apparently conflicting results concerning the vortex phase diagram of disordered hightemperature superconductors, which have led to the dichotomy elastic vortex glass − plastic
vortex assembly for the vortex phase at high magnetic fields.
4. Origin of the experimental order-disorder transition line curvature in the La2−xSrxCuO4 single
crystal vortex system at low temperatures
The dc magnetization curves of overdoped La2−xSrxCu2O4 single crystals in the low temperature T
range (down to 2 K) with the external magnetic field H oriented along the c axis were
investigated L.Miu, T.Adachi, Y.Koike, D.Miu, S.Diaz, and G.Chouteau, Phys. Rev. B 72,
052513, 2005]. It was found that the onset field for the second magnetization peak, associated
with the order-disorder transition in the vortex system, increases significantly with decreasing T
in the low-T region, where the superconductor parameters are independent of T. The upward
curvature of the order-disorder transition line determined in standard magnetization
measurements at low T is explained by considering the reduction of the actual pinning energy
due to the macroscopic currents induced in the sample. A simple energy balance equation for the
dynamic conditions generated in the widely performed magnetization studies is proposed.
5. Observation of interacting crossing vortex lattices in Bi2Sr2CaCu2O8+δ thin films
Scanning Hall probe microscopy and magnetometry has been used to study pancake vortices
(PVs) in highly anisotropic Bi2Sr2CaCu2O8+δ thin films A.Crisan, S.J.Bending, S.Popa, Z.Z.Li,
H.Raffy, Phys. Rev. B 72, 214509, 2005]. For small perpendicular applied fields we observe
well-defined PV stacks which are randomly pinned due to a high density of relatively strong
pinning centers in the films. When a strong in-plane magnetic field is added images reveal stripelike flux structures which are quite closely aligned to the in-plane field direction. We conclude
that this is a manifestation of Josephson vortex (JV) 'decoration' by PVs, which was recently
demonstrated in highly ordered BSCCO single crystals in the crossing lattices regime, allowing
independent estimates of the anisotropy parameter to be made. This interpretation is supported by
the observation that the presence of an in-plane field suppresses the irreversible magnetization of
thicker films. Estimates of the JV/PV crossing force and the PV pinning force are found to be
comparable in magnitude and fully consistent with this scenario. The existence of interacting
crossing vortex lattices in thin films with strong pinning could find potential applications in
superconducting devices.
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6. Influence of neutron irradiation on the (B0.65C0.35)Ba1.4Sr0.6Ca2Cu3Oz high-temperature
superconducting phase
Using transport and magnetization measurements the influence of neutron irradiation at a fluence
of 51017 ncm-2 on (B0.65C0.35)Ba1.4Sr0.6Ca2Cu3Oz
has been investigated [V.Mihalache,
A.Totovana, V.Sandu, S.Popa, G.Aldica, A.Iyo, J. of Supercond. 18(4), 461, 2005]. The
neutron irradiation was found to decrease the critical temperature and the bulk critical current
density, to increase the residual and normal-state resistivity, and to improve the intragranular
critical current density by 1.6×105 A/cm2 (at 77.3 K and in applied fields up to 160 kA). These
effects were discussed in terms of Bean-Livingstone surface barriers and geometrical barriers.
- Project title: Preparation of HTS by nonconventional methods, Partner: University of
California, Davis, California, USA
- Project title: Preparation of new HTS, Partner: IMR, Tohoku University, Sendai, Japan
- Project title: Normal state properties of HTS, Partner: Kent State University, Kent, Ohio, USA
- Project title: Self-assembling nanotechnology of pinning centers in HTS films for microwave
applications, Partner: ISG Juelich, Germany (Program THIOX, ESF)
- Project title: Vortex imaging (NATO Fellowship), Partner: Bilkent University, Ankara, Turkey
- Project title: Vortex dynamics in HTS at high magnetic fields, Partner: Johannes Gutenberg
University, Mainz, Germany
PAPERS PUBLISHED OR ACCEPTED FOR PUBLICATIONS IN 2005:
1.A.Crisan, A.Pross, D.Cole, S.J.Bending, R.Wördenweber, P.Lahl, E.H.Brandt, “Anisotropic
vortex channeling in YBa2Cu3O7-δ thin films with ordered antidot arrays”, Phys. Rev. B 71,
144504, 2005
2.L.Miu, T.Adachi, Y.Koike, D.Miu, S.Diaz, G.Chouteau, “Origin of the experimental orderdisorder transition line curvature in the La2−xSrxCuO4 single crystal vortex system at low
temperatures”, Phys. Rev. B 72, 052513, 2005
3.L.Miu, “Ordering of the creeping vortex system in in Bi2Sr2CaCu2O8 + δ single crystals at low
temperatures”, Phys. Rev. B 72, 132502, 2005 [Paper selected for the APS Virtual Journal of
Applications of Superconductivity, Vol. 9, Issue 9, November 1, 2005]
4.T.Katuwal, V.Sandu, C.C.Almasan, B.J.Taylor, M.B.Maple, “Vortex dissipation in
Y1−xPrxBa2Cu3O7−d superconductors above and below the zero-field critical temperature”, Phys.
Rev. B 72, 174501, 2005
5.A.Crisan, S.J.Bending, S.Popa, Z.Z.Li, H.Raffy, “Observation of interacting crossing vortex
lattices in Bi2Sr2CaCu2O8+δ thin films”, Phys. Rev. B 72, 214509, 2005
10
_____________________________________________________________________________
6.P.Badica, T.Kondo, K.Togano, “Superconductivity in a new pseudo-binary Li2B(Pd1-xPtx)3 (x =
0-1) boride system”, J. Phys. Soc. Jap. 74 (3), 1014, 2005
7.A.Crisan, S.J.Bending, A.Pross, A.Aziz, A.N.Grigorenko, R.G.Humphreys, “Flux structures
in mesoscopic YBa2Cu3O7-δ disks”, Supercond. Sci. Technol. 18, 207 (2005)
8.P.Badica, K.Togano, “Growth of superconducting and non-superconducting whiskers in the
Bi-Sr-Ca-Cu-O system”, J. Mater. Res. 20 (12), 3358, 2005
9.P.Badica, V.Sandu, G.Aldica, A.Iyo, H.Kito, M.Hirai, Y.Tanaka, “Fish-tail effect and
irreversibility field of (Cu,C)Ba2Ca3Cu4Ox-(LiF)y superconductor”, J. Supercond: 18 (4), 489,
2005
10.T.Kondo, P.Badica, Y.Nakamori, S.Orimo, K.Togano, G.Nishijima, K.Watanabe, “MgB2/Fe
superconducting tapes made using mechanically milled powders in Ar and H2 atmospheres”,
Physica C 426, 1231, Part 2, 2005
11.T.Kudo, Y.Nakamori, S.Orimo, P.Badica, K.Togano, “Hydrogen effects on synthesis
processes and electrical resistivities of LiBC”, J. Jap. Inst. Metals 69 (5), 433, 2005
12.K.Endo, P.Badica, “Preparation of stacked structures based on HTS by MOCVD: growth
problems of c-axis and non c-axis BiSrCaCuO/Bi4Ti3O12 heterostructures”, IEEE Trans. Appl.
Supercond. 15 (2), 3066, Part 3, 2005
13.V.Mihalache, A.Totovana, V.Sandu, S.Popa, G.Aldica, A.Iyo, “The influence of neutron
irradiation on (B0.65C0.35)Ba1.4Sr0.6Ca2Cu3Oz superconducting phase: the role of the grain edge”,
J. Supercond. 18(4), 461, 2005
14.V.Mihalache, “Anomalous splitting of the first penetration peak in the local magnetization
of Bi2Sr2CaCu2O8+y single crystals”, J.Optoelectron.Adv.Mater. 7, 3029, 2005
15.M.Velter-Stefanescu, O.G. Duliu, V.Sandu, “YBa2Cu3O7-d:Li superconductor system
investigated by direct microwave absorption method”, J.Optoelectron.Adv.Mater. 7, 973, 2005
16.M.Velter-Stefanescu, O.G.Duliu, N.Preda, “On the relaxation mechanisms of some radiation
induced free radicals in polymers”, J.Optoelectron.Adv.Mater. 7, 985, 2005
17.M.Velter-Stefanescu, O.G.Duliu, V.Mihalache, “Magnetically modulated microwave
absorption investigation of Bi1.8Pb0.4Sr1.8Ba0.2Ca2Cu3Ox/(LiF)y superconducting system”, J.
Optoelectron.Adv.Mater. 7, 1557, 2005
18.S.Polosan, E.Apostol, M.Secu, G.V.Aldica, “BGO glasses: structural and optical
characterization”, Physica Status Solidi C: Conferences and Critical Reviews 2(1), 93, 2005
19.V.Mihalache, S.Popa, D.DiGioacchino, P.Tripodi, J.D.Vinko, “Experimental evidence for a
dimensional crossover of the vortex ensemble in BSCCO (Bi1.8Pb0.4Sr1.8Ba0.2Ca2Cu3Ox) by multiharmonic AC susceptibility measurements”, Physica C (accepted)
11
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20.V.Sandu, S.Popa, D.DiGioacchino, P.Tripodi, “Evidence for irradiation triggered
nonuniform defect distribution in multiharmonic magnetic susceptibility of neutron irradiated
YBa2Cu3O7-d”, J. Supercond. (accepted)
CONFERENCES:
1.V.Sandu, T.Katuwal, C.C.Almasan, B.J.Taylor, M.B.Maple, “Scaling of conductivity through
the critical temperature in Y0.54Pr0.46Ba2Cu3O7”, 24th Int. Conf. on Low Temperature Physics, 1017 August 2005, Orlando, USA
2.V.Sandu, P.Gyawali, T.Katuwal, C.C.Almasan, B.J.Taylor, M.B.Maple, “Reentrant
irreversibility and magnetic transition in strongly underdoped Y0.47Pr0.53Ba2Cu3O7”, 24th Int.
Conf. on Low Temperature Physics, 10-17 August 2005, Orlando, USA
3.A.Crisan, P.Badica, S.Popa, L.Miu, “Self assembling nanotechnology of pinning centres in
superconducting films and devices”, 12th International Conference of Nonconventional
Technologies, ICNcT 2005, November 3-4, 2005, Bucharest, Romania, National Technologies
Review, no. 3, 121 (2005)
4.V.Sandu, S.Popa, E.Sandu, “Neutron-irradiated superconducting YBa2Cu3(Li)O7-δ with
improved irreversibility”, Proceedings of The 4th National Conference „New Research Trends in
Materials Science” Constanta, September 4-6, 2005, ARM-4, vol. I, 241, 2005
5.G.Aldica, C. Plapcianu, P.Badica, C. Valsangiacom, B. Popescu, „The magnetic effects in
Sr2FeMoO6 perovskite type compound obtained by soft chemistry”, Proceedings of The 4th
National Conference „New Research Trends in Materials Science” Constanta, September 4-6
2005, ARM-4, vol. II, 490, 2005
6.M.Chipara, J.Sankar, P.Notinger, D.Panaitescu, D.Hui, G.V.Aldica, M.D.Chipara, K.-T.Lau,
“Conducting and antistatic composites for space applications”, Materials Research Society
Symposium Proceedings 851 (Materials for Space Applications), 381, 2005
BOOKS:
1. Vortex Physics and Flux Pinning (Studies of High Temperatures Superconductors, Volume 48,
ISBN: 1-59454-304-6), Nova Science Publishers, NY, Ed. A. V. Narlikar, Chapter 2 “Effects of
the driving force born in magnetization measurements on the experimentally determined vortex
phase diagram of disordered HTS”, L. Miu, 2005
12
Laboratory of Semiconductor Physics
HEAD: Dr. IOANA PINTILIE
Tel.: (+4021) 493 01 95
Fax: (+4021) 493 02 67
TOTAL EMPLOYEES : 19
RESEARCH TEAM: 15
The laboratory contains 2 distinct groups.
A. GROUP OF SEMICONDUCTOR AND DIELECTRIC THIN FILMS
HEAD: Dr. IOANA PINTILIE
Tel.: (+4021) 493 01 95
Fax: (+4021) 493 02 67
RESEARCH TEAM: 13
1. Dr. Ioana PINTILIE
2. Dr. Toni BOTILA1
3. Dr. Lucian PINTILIE2
4. Dr. Eugenia PENTIA
5. Dr. Manuela BUDA
6. Dr. Bogdan MEREU4
7. Dr. Alfred GOLDENBLUM6
8. Dr. Iulian BOERASU9
9. Ion MATEI3
10. George SARAU5
11. Viorica DRAGHICI
12. Marian LISCA8
13. Andreia POPA7
senior researcher I
senior researcher I
senior researcher I
senior researcher I
1
Retired, only consultant, no formal employment
Actual address: MPI-Halle, Germany
3
Actual address: MPI-Stutgart, Germany
4
Actual address: IBM-Zürich, Elvetia
5
Actual address: Research Center, Jülich, Germany.
6
Retired, only consultant, no formal employment
7
Actual address: International Max Planck Research School, Dresden, Germany
8
Actual address: Friedrich-Schiller University, Jena, Germany
9
Actual address: Josef Stefan Institute, Slovenia
2
13
Photoelectric phenomena and field effect in complex dielectric(ferroelectric)-semiconductor
structures; photoelectric phenomena in A4B6 , A2B6, oxidic thin films, ternary semiconductor
compounds and semiconductor nano-crystals or nano-structured thin films; electric properties of
MIS structures.
Properties of ferroelectric crystals, ceramics, thin films and graded ferroelectric structures.
Trap investigation in semiconducting materials and structures; irradiation induced damages in Si
detectors.
Semiconductor detectors and optoelectronic components.
Conduction mechanisms in high-k dielectrics
1.Polar and transport phenomena in micro- and nanostructured ferroelectric layers
The CERES project 4-66/2004: The properties of PZT thin layers deposited on Pt-coated Si
using the sol-gel method were compared with properties of thin layers deposited epitaxially by
Pulsed Laser Deposition (PLD). The analysis shows a clear dependence of the electrical
characteristics on the thin film microstructure. A model explaining the observed behaviors was
proposed. The presence of deep trapping centers was evidenced by photocurrent measurements.
2.Nano-porous ferroelectric and nano-composites ferroelectric-semiconductor structures
The CERES project 4-252/2004: Porous thin films PZT 20/80 were obtained using the sol-gel
deposition method by initial hydrolysis and incorporation of different polymers in the precursor
solution up to 25 % porosity. Good ferroelectric properties were demonstrated. The strong
decrease of the dielectric constant associated with increasing porosity is very interesting for
pyroelectric applications. PbS nanocrystals was obtained by the Chemical Deposition Method
and characterized using optical absorption and photoelectric measurements. The significant
influence of the chemical bath’s temperature during the deposition process on the nanocrystal
properties was evidenced.
3.Defect engineering in Si: the role of oxygen on the resistance to radiation of Si based devices
The CERES project 4-144/2004: It was shown that the differences in the changes observed in the
effective doping concentration after irradiation of Epi Silicon with 2 x 1014 cm-2 24 GeV protons
can be explained by the balance between the formation of two types of defects: a deep acceptor
(the I center) and a shallow donor (the BD complex). It was also demonstrated that oxygen
enriched silicon and especially Cz and EPI silicon offer an unprecedented radiation tolerance,
opening new prospects in producing cost-effective radiation tolerant p-in-n detectors.
4.Insulators with high values of the dielectric constant
High-k dielectric materials are presently intensive investigated for replacing the silicon dioxide
layers in the next MOS transistor generation. In the frame of the FP5- INVEST project, ended in
October 2004, we performed electrical and photoelectrical characterization of Al/LaAlO3/Si and
Al/La2Hf2O7/Si structures. We have shown that SCL currents in thin insulator films can be
explained only by the presence of impurity channels situated near the Fermi level of the injecting
contact. We have also developed a new model to explain the parallel shift of the C-V
characteristics with frequency for samples having a high density of trapping centers.
14
Ongoing project:
RD50 – CERN “Radiation hard semiconductor devices for very high luminosity colliders”
Bilateral cooperation C18002 / 09.01.2006 “Bistable Donors in Si: identification and role in
terms of radiation hardness” between NIMP and Dipartimento di Energetica, Universita di
Firenze, Firenze, Italy
Other cooperations:
Josef Stefan Institute, Slovenia (ferroelectric thin films)
MPI, Halle, Germany (SEM, ferroelectric thin films)
Workshop COST Action 528, Final Meeting, Chemical solution deposition of thin films
TECHNOLOGIES AND SERVICES:
- trap investigation in semiconducting materials and structures using TSC and OCS methods
- low temperatures electric and photoelectric measurements
- optical and electrical characterization of visible and IR detectors
PAPERS PUBLISHED OR ACCEPTED FOR PUBLICATION IN 2005:
1.M.Lisca, L.Pintilie, M.Alexe, C.M.Teodorescu, “Thickness effect in Pb(Zr0.20Ti0.80)O3
ferroelectric thin films grown by pulsed laser deposition”, Applied Surface Science, p. 1335514, 2005
2.L.Pintilie, M.Alexe, "Ferroelectric-like hysteresis loop in nonferroelectric systems", Applied
Physics Letters, 87, 112903, 2005
3.L.Pintilie, M.Alexe, “Metal-Ferroelectric-Metal heterostructures with Schottky contacts: I
Influence of the ferroelectric properties”, J. Appl. Phys. 98, 124103-8, 2005
4.L.Pintilie, I.Boerasu, M.J.M.Gomes, T.Zhao, R.Ramesh, M.Alexe, “Metal-ferroelectric metal
heterostructures with Schottky contacts: II Analysis of the experimental current-voltage and
capacitive-voltage characteristics of Pb(Zr,Ti)O3 thin films”, J. Appl. Phys. 98, 124104-9, 2005
5.L.Pintilie, M.Lisca, M.Alexe, "Polarization reversal and capacitance-voltage characteristic
of epitaxial Pb(Zr, Ti)O3 layers", Applied Physics Letters, 86, 192902, 2005
6.Q.Gao, M.Buda, H.H.Tan, C.Jagadish, “Room-temperature operation of InGaAsN quantum
dot lasers grown by metalorganic chemical vapor deposition”, Electrochemical and Solid-State
Letters 8, no. 2, G57-G59, 2005
7.M.Buda, C.Jagadish,“Computation of the modal reflectivity for a partially etched mirror:
application for integration of a laser diode and a waveguide”, Applied Optics vol. 44, no. 6, p.
1039-1050, 2005
15
8.A.Goldenblum, I.Pintilie, M.Buda, A.Popa, T.Botila, A.Dimoulas, G.Vellianitis, “Space
charge limited current involving carrier injection into impurity bands of high-k insulators”,
Appl. Phys. Lett., vol. 86, pp. 203506, 2005
9.M.Bruzzi, ….., I.Pintilie, “Radiation-hard semiconductor detectors for Super LHC”,Nucl.
Instr. and Methods in Physics Research A vol. A541, p.189-201, 2005
10.M.Moll, … I.Pintilie, “Development of radiation tolerant semiconductor detectors for the
Super LHC”, accepted for publication in Nucl. Instr. and Methods in Physics Research A,vol.
A546, p. 99-107, 2005
11.I.Pintilie, M.Buda, E.Fretwurst, F.Honniger, G.Lindstrom, J.Stahl,“Radiation-induced
donor generation in epitaxial and Cz diodes”, Nucl. Instr. and Methods in Physics Research A
vol. A552, p. 56-60, 2005
12.E.Fretwurst, …., I.Pintilie, “Recent advancements in the development of radiation hard
semiconductor detectors for S-LHC”, Nucl. Instr. and Methods in Physics Research A vol. A552,
p. 7-19, 2005
13.A.Popa, M.Lisca, V.Stancu, M.Buda, E.Pentia, T.Botila, “Crystalline effects in PbS thin
films grown on glass substrates by Chemical Bath Deposition”, J.Optoelectron.Adv.Mater., in
press
14.A.Goldenblum, I.Pintilie, M.Buda, A.Popa, M.Lisca, T.Botila, V.Teodorescu,A.Dimoulas,
G.Vellianitis, “Electrical properties of as-grown Molecular Beam Epitaxy high-k gate
dielectrics deposited on Silicon” accepted for publication in Journal of Applied Physics
15.C.Berbecaru, H.V.Alexandru, L.Pintilie, A.Dutu, B.Logofatu, R.C. Radulescu, "Doped versus
pure TGS crystals", Materials Science and Engineering B 118(1-3), 141-146, 2005
16.L.Pintilie, I.Vrejoiu , D.Hesse, M.Alexe, "Polarization fatigue and frequency-dependent
recovery in Pb(Zr,Ti)O3 epitaxial thin films with SrRuO3 electrodes", Appl. Phys. Lett. accepted
for publication
17.I.Boerasu, B.E.Watts, F.Leccabue, “Morphological and optical investigation of lead
zirconate titanate (20/80) ultra-thin films” Journal of Microelectronics, Electronic Components
and Materials, 35, 109, 2005
CONFERENCES
1.L.Pintilie, M.Lisca, M.Alexe, “Epitaxial ferroelectric of PZT type: insulators or
semiconductors?”, 17th International Symposium on Integrated Ferroelectrics. ISIF'2005, 17-20
April, Shanghai, China
2.L.Pintilie, M.Lisca, M.Alexe, “Epitaxial-quality PZT: insulator or semiconductor?”,6th
International Balkan Workshop on Applied Physics, IBWAP'2005, 5-7 July, Constanta, Romania
3.L.Pintilie, M.Lisca, M.Alexe, “Analysis of the electric properties of epitaxial Pb(Zr,Ti)O3
films”, European Congress on Advanced Materials and Processes, EUROMAT'2005, 5-8
September 2005, Prague, Czech Republic, (oral)
16
4.M.Lisca, L.Pintilie, M.Alexe, “Thickness effect in Pb(Zr0.2Ti0.8)O3 ferroelectric thin films
grown by pulsed laser deposition”, E-MRS'2005 Spring Meeting, 31 May-3 June, Strasbourg,
France, (poster)
5.A.Popa, M.Lisca, V.Stancu, E.Pentia, M.Buda, T.Botila, “Crystallite size reduction effect
in PbS thin films grown on glass substrates by chemical bath deposition”, 6th International
Balkan Workshop on Applied Physics, IBWAP'2005, 5-7 July, Constanta, Romania, (poster)
6.A.Goldenblum, I.Pintilie, M.Buda, A.Popa, M.Lisca, T.Botila, A.Dimoulas, G.Vellianitis ,
“Conduction mechanisms in MIS structures with high-k insulator layers”, Nonconventional
Technologies Review vol. 3, p. 69-72, November 2005, Bucharest, Romania
7.V.Stancu, I.Boerasu, E.Pentia, M.Lisca, M.Buda, E.Ion, B.Malic, M.Kosec, “Effect of
porosity on ferroelectric properties of PZT 20/80 films”, Workshop COST action 528, section
Chemical Solution Deposition of thin films 13-15 Noiembrie 2005, Prague, Czech Republic
8.I.Boerasu, B.Malic, M.Mandeljc, M.Kosec, V.Bobnar, V.Sherman, T.Yamada, N.Setter,
“Structural and physical characterization of Ba0.3Sr0.7TiO3 thin films prepared by chemical
solution deposition”, Proceedings of 41th International Conference on Microelectronics, Devices
and Materials, P.107, 14-16 September 2005, Ribno at Bled, Slovenia
9.I.Boerasu, B.Malic, M.Mandeljc, M.Kosec, V.Sherman, T.Yamada, N.Setter, “Investigation
of low frequency dielectric response of polycrystalline Ba0.30Sr0.70TiO3 thin films prepared by
chemical solution deposition”, Workshop COST action 528, section Chemical Solution
Deposition of thin films 13-15 Noiembrie 2005, Prague, Czech Republic.
10.E.J.Danicki, F.S.Hickernell, I.Mateescu, “Closed-form solution for SPUDTs“, Proceedings
of IEEE Int. Frequency Control Symposium, Vancouver, Canada, p.152-155, 2005
11.I.Mateescu, B.Capelle, J.Detaint, G.Johnson, C.Bran, “Investigations by X-ray topography
of quartz and langasite resonators “, Journal de Physique IV, 126, p.3-6, 2005
12.I.Mateescu, C.Bran, S.Georgescu, “The influence of material constants on langasite
devices“, Proceedings of European Time and Frequency Forum, Besancon, France, p.188-192,
2005
EDUCATIONAL ACTIVITIES :
3 Ph.D. Theses in different phases of elaboration
B. GROUP OF RESONANT PIEZOELECTRIC STRUCTURES
HEAD: Dr. IRINA MATEESCU
17
Tel. : (+4021) 493 01 95
Fax : (+4021) 493 02 67
RESEARCH TEAM: 2
1. Dr. Irina Mateescu
2. Drd. Cristina Bran
- Vibration mode analysis by X-ray topography in quartz and langasite resonators
- Growth and characterization of langatate-a new piezoelectric crystal
- Mass-loading effects on electrical characteristics of GaPO4
- Characterization of langatate crystals by electron microscopy
1.The comparative study of the mass-loading influence on resonant structures characteristics
realized on various piezoelectric crystals.
Experimental results obtained by comparative analysis of quartz and langasite resonators allow
us to say that the influence of mass-loading on electrical characteristics of langasite crystal is
lower than in the case of quartz resonators. The behavior of resonator characteristics was
ascribed, depending on electrodes geometry, to the coupling of the thickness-shear with
thickness-twist modes of vibrations and to the stress at interface electrode-piezoelectric structure.
Due to this property of langasite crystal, that is an important advantage over quartz crystal, it is
possible to obtain high quality devices.
2.Characterization by electronic microscopy of langatate (LGT) crystal
By means of the transmission electron microscopy (TEM) and electron diffraction, some
structural properties of the LGT crystal have been evaluated at microscopic scale. In order to
identify the dislocation density from the crystal, etching experiments were performed whereas
the surface was consequently observed by optical or scanning electron microscopy (SEM). The
surface density and morphology of etch pits were correlated to dislocation density.
3.Mass-loading influence on characteristics of GaPO4 resonators
Four groups of plan-parallel AT-cut GaPO4 blanks of 14mm diameter and 5MHz fundamental
frequency have been used in experiments:1) lapped; 2) polished; 3) polished and thermally
treated; 4) lapped and thermally treated. On these blanks have been deposited by vacuum
evaporation Ag electrodes with 7mm diameter and 80, 150, 200nm thickness.
Using the relations for transmission-line equivalent electrical circuit, the effective mass-loading,
piezoelectric coupling coefficient, motional inductance, motional capacitance and quality factor
have been calculated. We used in our study the most important parameters: effective massloading, motional inductance and quality factor.
The experimental results revealed that the maximum variations of the effective mass-loading,
motional inductance and quality factor with harmonics, for various electrode thicknesses, are
influenced by the thermal treatment and by the finishing degree of the plates.
18
Agreement on Scientific Cooperation between:
- IMEL- Institute of Microelectronics, National Center for Scientific Research „Demokritos”
- Piezocryst Advanced Sensorics GmbH, Graz, Austria
and
- Group of Resonant Piezoelectric Structures from National Institute of Materials Physics
1. E.J.Danicki, F.S.Hickernell, I.Mateescu, “Closed-form solution for SPUDTs”, Proc. IEEE
Int. Frequency Control Symposium, p. 152-155, 2005
2.I.Mateescu, B.C.J.Detaint, G.Johnson, C.Bran, „Investigations by X-ray topography of quartz
and langasite resonators”, Journal de Physique IV, 126, p.3-6, 2005
3.I.Mateescu, C.Bran, S.Georgescu, ”The influence of material constants on langasite
devices”, Proc. of European Time and Frequency Forum, Besancon, France, p. 188-192, 2005
4.I.Mateescu, F.Krispel, C.Bran, “The investigation of the mass-loading influence on electrical
parameters of AT-cut GaPO4 resonators”, abstract submitted to European Time and Frequency
Forum 2006, Braunschweig, Germany
1 Ph.D. thesis in phase of elaboration
19
Laboratory of Solid State Magnetism
____________________________________________________________________________________________
_
HEAD: Dr. MIHAELA VALEANU
Tel : (+4021) 493 01 95
Fax: (+4021) 493 02 67
TOTAL EMPLOYEES : 28
RESEARCH TEAM : 21
A. GROUP OF ELECTRONIC PROCESSES VIA NUCLEAR
GAMMA RESONANCE
HEAD: Dr. GEORGE FILOTI
Tel: (+4021) 493 01 95
Fax: (+4021) 493 02 67
RESEARCH TEAM : 6
Dr. George FILOTI
Dr. Victor KUNCSER
Dr. Ovidiu CRISAN
Dr. Petru PALADE
Dr. Daniela PREDOI
Gabriel SCHINTEIE
senior researcher I
senior researcher I
1. Nano-particles and nano–phases, including composites, in various matrices (intermetallics,
polymers, oxides and vitreous media). Low dimensionality effects, including relaxation processes
and surface / interface mechanisms;
2. Molecular magnetism in metal-organic and co-ordination compounds. The electron hopping
processes, high spinlow spin transition, spin frustration, local structure versus thermal or
irradiation “annealing” behavior;
3. Magnetic and electric interactions in materials with various structures;
4. Polymers doped with multiple valence transitional metals for integrated optics (storage and
transmission media, real time holography) and gas sensors;
5. Spin structure at surface and interface. Exchange-bias and exchange spring phenomena in
binary and ternary systems. Spin structures and GMR effects in thin films and nanocomposites;
6. Computer simulations of electronic and magnetic properties in intermetallics and nanomaterials;
20
____________________________________________________________________________________________
_
7. Hydrogen storage in Mg-TM (transitional metal) intermetallics and complex hydrides. Corelation between microscopic structure and hydrogen storage properties ( absorption / de-sorption
kinetics and pressure-composition-isotherm (PCI) behaviour;
MAIN SCIENTIFIC RESULTS OBTAINED IN 2005 :
1. Nano-particles and nano –phases, including composites, in various matrices intermetallics,
polymers, oxides and vitreous media
Nano-composites of Fe oxides dispersed in silica matrix or aluminophosphate glasses doped with 3dtransition metal ions were prepared and analyzed by different methods. The influence of the thermal
annealing on the phase composition and grain size of the final products were studied via Mossbauer
spectroscopy and microscopic techniques. The microscopic parameters were correlated to the
magnetic ones. The optical and the electronic properties of the doped aluminophosphate glasses were
studied by optical and Mössbauer measurements for various transition metal doping ions. Local
magnetic phenomena and interparticle interactions were also studied in ferrofluids.
2. Molecular magnetism. Metal - organic and coordination compounds: electron hopping, high spinlow spin transition, spin frustration, local structure
Metal organic and coordination compounds assembled by carboxylate ligands and presenting
magnetic order at low temperature (below 80 K) were synthesized and studied by Mossbauer
spectroscopy and magnetometry.
3. Magnetic and electric interactions in materials with various structures
Structural phase transitions induced by high pressure were studied “in situ” by EDX using
Synchrotron facilities. Local interactions and coordination, valence state and oxygen deficiency
were studied in perovskites and double perovskites in connection with their catalytic and
magnetoresistive properties.
4. Iron doped polymers: local interactions and optical properties
The refractive index, the film thickness and the surface morphology of metal doped polymers
(from different sources, as salts and/or oxides) were analysed in function on the preparation
conditions and UV exposure characteristics. Atomic force microscopy experiments were used for
the study of the film thickness and morphology and optical interferometry for the evaluation of
the refractive index. The optical properties were related to electronic mechanisms studied by
Mössbauer spectroscopy.
5. Spin structure at surface and interface. Exchange-bias and exchange spring phenomena in bilayer systems
Thin magnetic films made of a soft magnetic Fe layer coupled to a hard magnetic FePt one,
separated by a non-magnetic spacer layer like Cu have been synthesised by dc magnetron
sputtering. If exposed to a non-collinear external field, the moments of the system form a
magnetic spiral in the soft magnetic layer. By the integration of a 57Fe probe layer in different
depths within the Fe layer and the use of coherent nuclear resonant scattering of synchrotron
radiation (at the European Synchrotron Radiation Facility (ESRF) Grenoble), the spin structure
and the coupling angle between the moments of successive layers have been adequately
21
____________________________________________________________________________________________
_
analysed. The interfacial spin structure in ferromagnetic/antiferomagnetic and soft magnetic/hard
magnetic nanocomposites was analysed mainly by Conversion Electron Mössbauer Spectroscopy
within the tracer layer technique. New systems presenting exchange bias phenomena were
prepared (e.g. Fe/FeSn2 and Fe/FeGdB). Thin films of Fe-Cu nanocomposites (Fe clusters in Cu
matrix) with various Fe content were prepared via thermo-ionic vacuum arc. The electric transport
properties are studied by four points methods and the structure, morphology and the magnetic
behaviour of the Fe clusters, by X-Ray Diffraction, Atomic Force Microscopy, Transmission Electron
Microscopy and Temperature Dependent Mössbauer Spectroscopy.
INTERNATIONAL COOPERATION & PROJECTS:
1. Network of Excellence, within the European Commission Frame Programme 6
Project Title: Molecular Approach to Nanomagnets and Multifunctional Materials, MAGMANet,
Romania , promoter Dr. George Filoti
2. NATO- Collaborative Linkage Grant in cooperation with University of Le Mans, France and
University of Thessaloniki, Greece.
Project title: “Novel magnetic nanostructures for sensor fabrication” 2004 –2006 Romanian
Investigators: Dr. George Filoti, Dr. Ovidiu Crisan
3. Bilateral co-operation, via CNRS-Romanian Academy agreement with University du Maine,
Le Mans (CNRS), France
Project title: “Conception de nouveaux matériaux à fort effet de surface” 2004- 2005, Promoter:
Dr. George Filoti, Romanian Co-director : Dr. Ovidiu Crisan
4. Bilateral agreement with University of Duisburg, Germany
Project title: Local structure and magnetic intéractions in composite materials with surface
properties (2002-2006), Promoter: Dr. Victor Kuncser
5. Bilateral cooperation agreement with Rostock University, Germany, Two laboratories
involved: “Solid State Magnetism” and “Structure and Dynamics of Solids”
Project title: “Synthesis and characterization of nanostructured materials with advanced
functionalities” (2004- 2008) Promoter Dr. Florin Vasiliu,
PAPERS PUBLISHED OR ACCEPTED FOR PUBLICATION IN 2005 :
1.V.Kuncser, R.Nicula, U.Ponkratz, A.Jianu, M.Stir, E.Burkel, G.Filoti, “Structural phase
transitioninduced in Fe50Rh50 alloys by high pressure” Journal. of Alloys and Comp., 386 (1-2) 8,
2005
2.V.Kuncser, M.Valeanu, F.Lifei, D.Predoi, A.Jianu, W.Kappel, M.Codescu, E.Patroi, I.Pasuk,
M.Bulinski, G.Filoti, „Micro-structure and magnetic properties of Fe-Cu nanocomposites for
anisotropic permanent magnets” Journal. of Alloys and Comp., 395(1-2) 1 2005
3.V.Kuncser, F.Stromberg, M.Acet, W.Keune, „Mossbauer effect study of correlation between
structure and exchange bias effect in ferromagnetic Fe/antiferromagnetic FeSn2 bilayers”,
J.Appl. Phys., 97(6) 063513, 2005
4.P.Palade, G.Principi, T.Spataru, P.Blaha, K.Schwarz, V.Kuncser, S.Lo Russo, S. Dal Toe,
V.A.Yartys, “Mössbauer study of LaNiSn and NdNiSn compounds and their deuterides”, in
print, J. Radioanal. Nucl. Chem.
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5.T.Spataru, P.Palade, G.Principi, P.Blaha, K.Schwarz, V.Kuncser, S. Lo Russo, S. Dal Toé,
V.A. Yartys, “The nature of the hydrogen bond in the LaNiSnH2 and NdNiSnH hydrides”,
J.Chem.Phys.122 (12) 124703, 2005
6.M.Raileanu, M.Crisan, C.Petrache, D.Crisan, A.Jitianu, M.Zaharescu, D.Predoi, V.Kuncser,
G.Filoti, „Sol-gel FexOy-SiO2 nanocomposites”, Rom.J.Phys., 5-6 (50), 2005
7.M.Elisa, C.E.A.Grigorescu, C.Vasiliu, M.Bulinski, V.Kuncser, D.Predoi, G.Filoti, A.Meghea,
N.Iftimie, M.Giurginca, „Optical and electronic properties of the aluminophosphate glasses
doped with 3d-transition metal ions”, Reviews on Advanced Materials Science, 366-367, 10 (4),
2005
8.C.P.Lungu, I.Mustata, A.M.Lungu, O.Branza, V.Zoroschi, V.Kuncser, G.Filoti, L.Ion, „Giant
magnetoresistence effects in correelation with local magnetic interaction in Fe-Cu and Co_cu
granular thin films prepared by thermionic vacuum arc method”, J.Optoelectron.Adv.Mater.,
2507-2512 (7(5), 2005
9.V.Kuncser, I.Mustata, C.P.Lungu, A.M.Lungu, V.Zoroschi, W.Keune, B.Sahoo, F.Stromberg,
M.Walterfang, L.Ion, G.Filoti, „Fe-Cu granular thin films with giant magnetoresistence by
thermionic vacuum arc method: Preparation and structural characterization”, Surface and
Coating Technology, 980-983 (1-4) 2005
10.P.Palade, G.Principi, T.Spataru, P.Blaha, K.Schwarz, V.Kuncser, S.Russo, S. Dal Toe, V.A.
Yartis, „Mossbauer study of LaNiSn and Nd Ni Sn componds and their deuterides”,
J.Optoelectron.Adv.Mater., 553-556, 266(3), 2005
11.F.Stromberg, W.Keune, V.Kuncser, K.Westerholt, „Fe-coverage-induced out-of – plane spin
components of the antiferromagnetic spin structure in exchange-biased Fe/FeSn2 bilayers”,
Physical Review 72 (6), 064440, 2005
12.U.Russo, L.Nodari, M.Faticanti, V.Kuncser, G.Filoti, „Local interactions and phenomena in
substituded LaFeO3 perovskites”, Solid State Ionics, 97-102, 176 (1-2), 2005
13.E.E.Tornau, V.Petrauskas, O.Crisan, „Effect of surface anisotropy in core-shell bimetallic
nanoparticles”, Acta Physica Polonica, 425-428, 107(2), 2005
14.D.Predoi, V.Kuncser, M.Zaharescu, A.Jitianu, M.Crisan, W.Keune, B.Sahoo, G.Filoti,
„FexOYSiO2
nanocomposites
studied
by
Mössbauer
spectroscopy”,
in
print
J.Optoelectron.Adv.Mater.
15.V.Kuncser, W.Keune, F.Stromberg, G.Schinteie, G. Filoti, „Spin configuration in exchange
coupled magnetic phases studied by Mössbauer spectroscopy”, in print J.Optoelectron.
Adv.Mater.
16.P.Palade, G.Princcipi, S.Sartori, A.Maddalena, S. Lo Russo, G.Schinteie, V.Kuncser,
G.Filoti, „Mossbauer study of Mg-Ni(Fe) alloys processed as materials for solid state hydrogen
storage”, in print Hyperfine Interaction
23
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_
17.B.Sahoo, V.Kuncser, W.Keune, J.Pieper, „Mossbauer spectroscopical investigation of
amorphous Fe0.3Y0.7 alloy ribons prepared by melt spinning”, in print Hyperfine Interaction
18.O.Crisan, A.D.Crisan, R.Nicula, E.Burkel, „Thermally and pressure activated phase
evolution in Fe-Pt-Nb-B melt spun ribbons”, Hasylab-Desy Annual Report 2005, in print
19.O.Crisan, M.Angelakeris, Th.Kehagias, Ph.Komninou, E.Papaioannou, N.Sobal, M.Giersig,
N.K.Flevaris, “Ag/Co bimetallic nanoparticles: morphology, structure and anomalous magnetic
behavior”, Acta Materialia, in print
20.O.Crisan, J.M. Le Breton, A.D.Crisan, G.Filoti, “Study of crystallization processes in Gdsubstituted Finemet alloys", J. Alloys & Comp. in print
21.T.Klein, O.Crisan, K.Schlage, R.Röhlsberger, E.Burkel, “Magnetic structure and exchange
coupling of spring magnets - using nuclear resonant scattering”, Thin Solid Films, in print
CONFERENCES :
1.D.Predoi, V.Kuncser, M.Zaharescu, A.Jitianu, M.Crisan, W.Keune, B.Sahoo, G.Filoti,
„FexOY –SiO2 nanocomposites studied by Mössbauer spectroscopy”, A 4–a Conferinta Nationala
"Directii noi de cercetare in stiinta materialelor”, ARM–4, Constanta, septembrie, 2005,
Romania
2.V.Kuncser, W.Keune, F.Stromberg, G.Schinteie, G.Filoti, „Spin configuration in exange
coupled magnetic phases studied by Mössbauer spectroscopy”, A 4–a Conferinta Nationala
"Directii noi de cercetare in stiinta materialelor” , ARM – 4, Constanta, septembrie, 2005,
Romania
3.P.Palade, G.Princcipi, S.Sartori, A.Maddalena, S. Lo Russo, G.Schinteie, V.Kuncser,
G.Filoti, „Mössbauer Study of Mg-Ni(Fe) alloys processed as materials for solid state hydrogen
storage”, ICAME, 5-9 september, Montpellier, France, 2005
4.B.Sahoo, V.Kuncser, W.Keune, J.Pieper, „Mössbauer spectroscopical investigation of
amorphous Fe0.3Y0.7 alloy ribbons prepared by melt spinning”, ICAME, 5-9 september,
Montpellier, France, 2005
5.V.Kuncser, G.Schinteie, B.Sahoo, W.Keune, D.Bica, L.Vekas, G.Filoti, „Complex
caracterisation os magnetic fluids by Mossbauer Spectroscopy”, Second International workshop
„Magnetic Nanofluids”, Timisoara, 2005
6.M.Alifanti, M.Florea, G.Filoti, V.Kuncser, V.Cortes-Corberan, V.I.Parvulescu, „In-situ
structural changes during toluene complete oxidation on suppported EuCoO3 by monitored by
151
Eu Mossbauer spectroscopy”, 5th World Congress on Oxidation Catalysis, sept 25-30,
Sapporo, Japan
7.O.Crisan, M.Valeanu, A.D.Crisan, F.Lifei, N.Randrianantoandro, E.Burkel, “Formation and
stability of magnetic nanostructures in nanocomposite melt-spun Fe-Pt-Nb-B ribbons”, 3rd
International Conference on Materials for Advanced Technologies and 9th International
Conference on Advanced Materials, ICMAT & ICAM 2005, Singapore, July 2005
24
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_
8.T.Klein, O.Crisan, K.Schlage, R.Röhlsberger, E.Burkel, “Magnetic structure and exchange
coupling of spring magnets - using nuclear resonant scattering”, 3rd International Conference
on Materials for Advanced Technologies and 9th International Conference on Advanced
Materials, ICMAT & ICAM 2005, Singapore, July 2005
9.O.Crisan, M.Angelakeris, N.Randrianantoandro, M.Valeanu, G.Filoti, “Hybrid FePt/Fe3B
exchange-coupled nanocomposite magnets”, 12th International Symposium on Metastable and
Nano Materials, ISMANAM Paris, July 2005
10.O.Crisan, N.Randrianantoandro, J.M.Grenèche, A.D.Crisan, M.Valeanu, E.Burkel,
“Synthesis and characterization of melt spun Fe-Pt-Nb-B nanocomposite magnets”, 12th
International Symposium on Metastable and Nano Materials, ISMANAM Paris, July 2005
- Ph.D. promoter - Dr.G.Filoti: 4 Ph.D. theses in different phases of elaboration
B.GROUP OF RARE-EARTH MAGNETIC COMPOUNDS
HEAD : Dr. MIHAELA VALEANU
Tel : (+4021) 493 01 95
Fax: (+4021) 493 02 67
RESEARCH TEAM : 11
Dr. Mihaela VALEANU
Dr. Dorin Petru LAZAR
Dr. Mircea MORARIU
Dr. Neculai PLUGARU
Dr. Andrei GALATEANU
Dr. Marilena TOMUT
Dr. Stanica ENACHE
Mihaela SOFRONIE
Felicia LIFEI
Bogdan POPESCU
Alina CRISAN
senior researcher I
senior researcher I
senior researcher I
senior researcher I
PRESENT RESEARCH INTERESTS :
Magnetic phenomena in 3D nanosized systems
Intermetallics, crystalline and amorphous alloys. Kinetic of crystallization; structural relaxation. Rare
Earth-Iron nanocomposite magnetic materials
Magnetic contributions in iron – rare earth intermetallic compounds
Magnetic behaviour of hexagonal layered NaFeO2 and LiFeO2 oxides with Co substitutions
Preferential substitutions of Al ions in layered Gdm+n(Co,Al)5m+3nB2n system.
25
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5f electron magnetism in U based intermetallic compounds
Magnetism, critical behaviour and superconductivity in heavy fermion compounds
1. Magnetic phenomena in 3D nanosized systems
The Fe-Pt-rich alloys may potentially develop the hard magnetic L10 (also denoted γ1) phase
directly by casting the melt during a rapid solidification process. The L10 ordered face-centeredtetragonal γ1-FePt phase with very high magnetocrystalline anisotropy (7 MJ/m3) is responsible
for the good permanent magnetic behavior of the system. A further improvement of the energetic
product (BH)max may be obtained by dispersing this hard magnetic phase into a soft magnetic
matrix of either Fe3Pt and/or Fe3B phases, in the form of a homogeneous magnetic
nanocomposite exchange spring – type melt spun ribbon. Several Fe-Pt-Nb-B alloys with
different nominal compositions have been synthesised by rapid quenching of the melt. The phase
evolution with temperature and pressure in the as-cast ribbons has been monitored by energy
dispersive X-ray diffraction with synchrotron radiation at Desy-Hasylab MAX 80 beamline. A
partial disorder – order phase transformation with occurrence of hard magnetic L10 phase, is
observed.
-Magnetic nanocomposites based on SmCo5/α-Fe have been synthesized by the mechanical
alloying followed by appropriate heat treatments; the best enhanced magnetic properties were
obtained on samples with 18nm grain size and soft phase dimension of 7-8nm .
2. Magnetic Behavior of Hexagonal LiFeO2 system with Co Substitution
Layered structure oxides of the system LiFe1-xCoxO2 were prepared for 0 ≤ x ≤ 0.7 by ionexchange reaction in a molten eutectic mixture of LiCl and LiNO3 at 260oC. The magnetic
properties were studied by magnetic and Mössbauer measurements in the temperature range 4.2 –
300 K. The susceptibility and Mössbauer data point to a spin glass magnetic behavior of the
LiFe1-xCoxO2 system showing a hexagonal α-NaFeO2 structure. In this layered structure, a
relatively large distance separates the successive Fe3+ hexagonal planes and consequently the
main Fe - O - Fe antiferromagnetic couplings take place between Fe3+ neighbors via the O2- ions
from the upper and lower neighboring O2- layers. Since Co3+ is in its usually diamagnetic low
spin state, the Co substitution for Fe is equivalent to an increasing magnetic dilution. The
Mössbauer spectra function of Co concentration and temperature suggested a two-dimensional
clustering, growing isotropically around Fe-centered hexagon. The hyperfine fields, spin freezing
temperatures and relaxation behavior plead for similar cluster size over whole Co concentration
range. The experimental results disagree with a substitution model based on a random (binomial)
distribution of Fe and Co over the corresponding hexagonal layers, which should give rise to
drastic modification of the magnetic properties and Mössbauer interaction in dependence on
composition.
3. Magnetism, critical behaviour and superconductivity in heavy fermions compounds
In the vicinity of a quantum critical point (QCP) the behaviour of heavy fermion compounds is
strongly affected by quantum fluctuations, giving rise to new interesting features which can be
observed and analysed using different experimental techniques. The emergent behaviour of the
compounds close to a QCP is characterised by strong instabilities of the ground state. Often the
electrons tend to "avoid" such an unstable states and therefore they condense in a more stable
state (superconducting , quadrupolar order, etc.).
26
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4. Magnetotransport properties of switchable mirrors
Among various materials known nowadays, the thin films of metal-hydrides are the most
spectacular as they exhibit a remarkable transition upon hydrogen absorption, from shiny metals
to transparent and semiconducting. In literature, these systems are reffered as switchable mirrors.
Very different from bulk-hydrides, the metal-to-semiconductor transition exhibited by thin films
is reversible and can be driven for many times in moderate gaseous environments (at pressure far
below 1 bar at room temperature). This offers the unique opportunity to study in detail their basic
physical properties, impossible to be carried out on bulk samples as they often fall in parts upon
hydrogenation. In the aim to study the spectacular optical changes of thin metal-hydride films
exhibited upon hydrogen absorption, we make use of basic research tools that allow to describe
best the metal-to-semiconductor transition in metal-hidride films: characterization of the
structural, electrical (resistivity and Hall effect) and optical (transmission and reflection)
properties as a function of hydrogen concentration in the sample.
PROMOTED INTERNATIONAL COOPERATION & PROJECTS:
ESF COST action P16 ECOM (Emergent behavior in correlated matter) 2005-2009, Romanian
member in MC Dr. A. Galatanu
Bilateral agreement with Institut fur Oberflachen und Dunnschichttechnik (IfOD) Hochschule
Wismar, Germany, Project title: “Structural and magnetoresistive effect investigations in
double perovskites”
Bilateral agreement with BarIlan University, Department of Chemistry, Ramat Gun, Israel.
Project title: ” Nanomaterials and nanocomposites for special application”.
PAPERS PUBLISHED OR ACCEPTED FOR PUBLISHING IN 2005 :
1.D.P.Lazar, N.Plugaru, M.Valeanu, A.Galatanu, R.M.Leonovici, A.Dafinei, L.Ion,
“Magnetic and Mössbauer spectroscopic study of R3Fe29-xMox (R = Y, Nd, Sm, Gd, Tb, and Dy”,
Journal of Alloys and Compounds, 392, 31-39, 2005
2.V.Kuncser, M.Valeanu, F.Lifei, D.Predoi, A.Jianu, W.Kappel, M.Codescu, E.Patroi, I.Pasuk,
M.Bulinski, G.Filoti, „Micro-structure and magnetic properties of Fe-Cu nanocomposites for
anisotropic permanent magnets” Journal. of Alloys and Comp., 395(1-2) 1 2005
3.D.P.Lazar, N.Plugaru, V.Kuncser, M.Valeanu, G.Filoti, J.Bartolomé, J.Rubín, “Mössbauer
spectral study of RFe11.3W0.7 compounds (R = Dy, Ho, Er, and Lu)”, in print at Journal of
Magnetism and Magnetic Materials
4.N.Plugaru, J.Rubín, J.Bartolomé, C.Piquer, “Sructural and magnetic investigation of the
Nd3Co13-xNixB2 compounds”, Journal of Magnetism and Magnetic Materials., 290-291, 15631566, 2005
5.N.Plugaru, J.Rubin, J.Bartolomé, V.Pop, “X ray diffraction and magnetic measurements of
itinerant electron magnetism in the Y3Ni13-xCoxB2 system”, Phys. Rev. B 71, 024433(1-13), 2005
27
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6.D.Eniu, D.Cacaina, M.Coldea, M.Valeanu, S.Simon Structural and magnetic properties of
CaO-P2O5-SiO2-Fe2O3 glass-ceramics for hyperthermia”, Journal of Magnetism and Magnetic
Materials. 293, 310-313, 2005
7.T.D.Matsuda, Y.Haga, S.Ikeda, A.Galatanu, E.Yamamoto, H.Shishido, M.Yamada,
J.I.Yamaura, M.Hedo, Y.Uwatoko, T.Matsumoto, T.Tada, S.Noguchi, T.Sugimoto, K.Kuwahara,
K.Iwasa, M.Kohgi, R.Settai, Y.Onuki, "Electrical and magnetic properties of a single crystal
UCu2Si2", J.Phys.Soc.Japan 74, p.1552-1556, 2005
8.A.Galatanu, Y.Haga, T.D.Matsuda, S.Ikeda, E.Yamamoto, D.Aoki, T.Takeuchi, Y.Onuki,
"High temperature magnetic investigations on Uranium compounds", J.Phys.Soc.Japan 74,
p.1582-1597, 2005
9.Y.Okuda, T.Yamamoto, D.Honda, H.Shishido, A.Galatanu, Y.Haga, T.D.Matsuda,
T.Takeuchi, K.Kindo, K.Sugiyama, R.Settai, Y.Onuki, "CEF-scheme of a semimetal Ce3Sn7",
Physica B 359-361, p.323-325, 2005
10. N.Metoki, K.Kaneko, T.D.Matsuda, A.Galatanu, T.Takeuchi, S.Hashimoto, T.Ueda,
R.Settai, Y.Onuki, N.Bernhoeft, "Magnetic structure and crystal field excitation in heavy
fermion superconductor CePt3Si", Physica B 359-361, p.383-385, 2005
11.Y.Haga, T.D.Matsuda, S.Ikeda, A.Galatanu, T.Matsumoto, T.Sugimoto, T.Tada, S.Noguchi,
Y.Onuki, "Single-crystal growth and magnetic properties of a new ternary uranium compound
U3Ni5Al19", Physica B 359-361, p.1006-1008, 2005
12.S.Ikeda, Y.Tokiwa, T.D.Matsuda, A.Galatanu, E.Yamamoto, A.Nakamura, Y.Haga,
Y.Onuki, "Magnetic properties of UTGa5 (T: transition metal)", Physica B 359-361, p.10391041, 2005
13.T.D.Matsuda, Y.Haga, S.Ikeda, A.Galatanu, Y.Onuki,"Antiferromagnetic and ferromagnetic
phases of UCu2Si2", Physica B 359-361, p.1069-1071, 2005
14.S.Ikeda, Y.Onuki, T.D.Matsuda, A.Galatanu, E.Yamamoto, Y.Haga, et al., "Crossover from
itinerant character to localized behaviour of the 5f electronic states in UPtGa5", autori: topic
paper (japanese lang.) in Kotaibuturi 40, p.343-351, 2005
15.S.Enache, T.Leeuwerink, A.F.Th Hoekstra, A.Remhof, N.J.Koeman, B.Dam, R.Griessen,
“Electrical and optical properties of epitaxial YHx switchable mirrors”, J.Alloys Compd. 397, 916, 2005
16.M.Sorescu, L.Diamandescu, M.Valeanu,“Substitutional effects in RFe3 Intermetallics
(R=Dy, Sm, Y”, Intermetallics (in print)
17.M.Raekers, K.Kuepper, I.Balasz, H.Hesse, S.Constantinescu, E.Burzo, M.Valeanu,
M.Neuman, „Investigation of chemical and grain boundariy effects in highly ordered
Sr2FeMoO6: XPS and Mössbauer studies” accepted in J.Optoelectron.Adv.Mater.
18.O.Crisan, A.D.Crisan, R.Nicula, E. Burkel, „Thermally and pressure activated phase
evolution in Fe-Pt-Nb-B melt spun ribbons”,Hasylab-DESY Annual Report 2005, in print
28
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_
19.O.Crisan, J.M. Le Breton, A.D.Crisan, G.Filoti, “Study of crystallization processes in Gdsubstituted Finemet alloys", J. Alloys & Comp. in print
20.F.Lifei, C.P.Cristescu, A.Toma, M.Sofronie, “YAG-Nd laser irradiation effects on phase
structure modification in partially crystallized Fe78B13Si9”.in print JOAM
CONFERENCES :
1.O.Crisan, M.Valeanu, A.D.Crisan, F.Lifei, N.Randrianantoandro, E.Burkel, “Formation and
stability of magnetic nanostructures in nanocomposite melt-spun Fe-Pt-Nb-B ribbons”, 3rd
International Conference on Materials for Advanced Technologies and 9th International
Conference on Advanced Materials, ICMAT & ICAM 2005, Singapore, July 2005
2.O.Crisan, M.Angelakeris, N.Randrianantoandro, M.Valeanu, G.Filoti, “Hybrid FePt/Fe3B
exchange-coupled nanocomposite magnets”, 12th International Symposium on Metastable and
Nano Materials, ISMANAM Paris, July 2005
3.O.Crisan, N.Randrianantoandro, J.M.Greneche, A.D.Crisan, M.Valeanu, E.Burkel,
“Synthesis and characterization of melt spun Fe-Pt-Nb-B nanocomposite magnets”, 12th
International Symposium on Metastable and Nano Materials, ISMANAM Paris, July 2005
4.A.Galatanu, B.Popescu, E.Bauer, "Magnetoresistivity evolution near the quantum phase
transition in some Ce and Yb based intermetallic compounds", 6th International Balkan workshop
on applied physics (Constanta, Romania, July 5-7, 2005)
5.S.Enache, M.Sofronie, B.Popescu, A.Galatanu, M.Valeanu, "Remarkable switching
behavior in composite Gd-Fe-hydrides", 6th International Balkan workshop on applied physics
(Constanta, Romania, July 5-7, 2005)
6.F.Lifei, M.Sofronie, A.Jianu, M.Valeanu,V.S.Teodorescu, M.G.Blanchin, "Electrical and
structural study on Ni47Ti44Nb9shape memory alloy" 6th International Balkan workshop on
applied physics (Constanta, Romania, July 5-7, 2005)
7.B.Popescu, "Structural and magnetic study of colossal magnetoresistive magnetite thin
films”,
6th International Balkan workshop on applied physics (Constanta, Romania, July 5-7, 2005)
8.A.Galatanu, E.Yamamoto, Y.Hagaand, Y.Onuki, "Magnetic behaviour of UB4 at high
temperatures", SCES’05 - International Conference on Strongly Correlated Electron Systems
(Vienna, Austria, July 26-30, 2005)
9. A.Galatanu, "Low and high temperature magnetism in U-based intermetallics", New research
trends in materials science - ARM 4 (Constanta, Romania, September 4-6, 2005)
10.B.Popescu, M.Sofronie, F.Tolea, S.Enache, A.Galatanu, M.Valeanu, "Structural and
magneto-electric properties of Sr2FexCo1-xMoO6", New research trends in materials science ARM 4 (Constanta, Romania, September 4-6, 2005)
11.V.Teodorescu, M.Valeanu, A.Jianu, F.Tolea, M.Sofronie, A.Maraloiu, MG.Blanchin,
“TEM Study of the crystallization process on some magnetic nanocomposites” New research
trends in materials science - ARM 4 (Constanta, Romania, September 4-6, 2005)
29
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12.A.Galatanu, "5f magnetism in U based intermetallics",CNF - National Conference on
Physics, Bucharest, Romania, September 13-16, 2005
13.M.Sofronie, "Micro-structure and magnetic properties of Fe-Cu nanocomposites, as
potential candidates for RE-free permanent magnets", NANOMAT 2005, Network for
Nanostructured Materials of ACC, Iasi, Romania, 24-25 martie 2005
14.F.Tolea, C.P.Cristescu, A.Toma, M.Sofronie, "YAG-Nd laser irradiation effects on structure
in partially Fe78B13Si9 ",The 12th International Conference of Nonconventional Technologies,
ICNcT 2005,Bucharest
15.I.Mihalca, V.Kuncser, M.Valeanu, A.Ercuţa, I.Damian, M.Sofronie, G.Schinteie,“Structural
and magnetoelastic properties of amorphous Fe-Co-Sm-B alloys” ,14th National Conference on
Physics, Bucharest, 13-17 September 2005
16.G.Filoti, D.P.Lazar, M.Rosenberg, V.Kuncser, S. Kemmler-Sack, “Magnetic behaviour of
hexagonal LiFeO2 sistem with Co substitution”, 14th National Conference on Physics, Bucharest,
13-17 September 2005, Abstract volume 1, p. 51
C. GROUP OF NON-EQUILIBRIUM MATERIALS AND PROCESSING
HEAD:Dr. ADRIAN JIANU
Tel: (+4021) 493 01 95
Fax:(+4021) 493 02 67
RESEARCH TEAM: 2
Dr. Adrian JIANU
Dr. Mihaela Carmen BUNESCU
1.Material processing: physical vapour deposition, chemical vapour deposition, rapid
prototyping, chemical synthesis
2.Materials under investigation: synthesis of new materials by tailoring of structure at the
nano-scale: carbon-based nanostructures, materials for fuel cells and hydrogen storage, functional
gradient materials, amorphous carbon thin films
3.Characterisation methods: light and electron microscopy, mechanical testing, X-ray
diffraction and spectroscopy, impedance spectroscopy
1. Microstructural investigation of nano-catalyst particles
30
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Preparation and properties of catalysts nano-particles; electroless deposition on multi-wall carbon
nano-tubes (MWCNT); surface activation of the carbon nanotubes; characterization of
morphology and size distribution of the nano-catalyst (Research project at Hochschule Wismar)
2. Plasma treatment of polymer electrolyte membrane for fuel cells
Surface morphology / topography modification of polymer membrane by plasma etching;
influence of the plasma parameters: influence on the ionic conductivity of the membraneelectrode-assembly (Research project at Hochschule Wismar)
3. Carbon nanostructures produced by CCVD with induction heating
The catalytic chemical vapor deposition (CCVD) method in which the outer furnace is replaced
by the high frequency induction heating (IH) has been used for synthesis of carbon
nanostructures. Using different catalysts, various types of carbon nanofibers were obtained, with
the absence of the catalyst particles at their tip as a common characteristic. The IH mode
combined with the CCVD method seems attractive for the synthesis of carbon nanostructures,
allowing a significant decrease of energy consumption and of the overall reaction time as
compared with the heating mode with outer furnace.
4. Materials for Generation IV nuclear reactors
The specific objective of the project is the establishment of fundamental knowledge, theory and
models needed to solve materials-related feasibility issues for GEN IV nuclear reactors.
The performance of structural materials is limited, in general, by the degradation of physical and
mechanical properties due to the exposure to energetic neutrons, high-temperature and highpressure, or by exposure to the chemical environment provided by the primary coolant medium.
In order to accomplish the specific objective, the proposed activities could be classified as
follows: (i) production and properties analysis of ceramics and ceramic composites made of lowactivation elements; (ii) development of new approaches for the acceleration of irradiation tests;
(iii) irradiation test on significant low activation ceramics and ceramic composites.
PROMOTED INTERNATIONAL COOPERATION & PROJECTS:
Bilateral agreement with Hochschule Wismar,Germany, Project title: Structural and magnetoresistive effect investigations in double perovskites; phase transition in shape-memory alloys
PAPERS PUBLISHED OR ACCEPTED FOR PUBLISHING IN 2005:
1.M.Wienecke, M.C.Bunescu, K.Deistung, P.Fedtke, E.Borchartd, “MWCNT coatings obtained
by thermal CVD using ethanol decomposition”, accepted at Carbon (Available online via
ScienceDirect, DOI information: 10.1016/j.carbon. 2005.09.020)
2.B.Rohland, M.C.Bunescu, M.Pietrzak, M.Wienecke, T.Barfels, S.Möller,”CNT-based
cathode material for DMFC”, Fullerenes, Nanotubes and Carbon Nanostructures, 13(1), 511 –
522, 2005
31
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_
3.V.Kuncser, M.Valeanu, F.Lifei, A.Jianu, D.Predoi M.Codescu, W.Kappel, G.Filoti “Microstructure and magnetic properties of Fe-Cu nanocomposites as potential candidates for R EFree permanent magnets”, J. of Alloys and Commpounds 395 (1-2),1-6, 2005
transition induced in Fe50Rh50 alloys by high pressure”, J. of Alloys and Compounds 386, 8–11,
2005
CONFERENCES:
1.M.C.Bunescu, M.Wienecke, B.Rohland, B.Ruffmann, M.Pietrzak, S.Möller, “Carbon
nanotubes supported catalysts for DMFC”, E-MRS Spring Meeting, Strasbourg, May 31 – June
3, SYMPOSIUM L – Hydrogen and Fuel Cells, Oral presentation L-V.04, 2005
D.GROUP OF NEW SYTEMS WITH IONIC AND CO-ORDINATION BOND
HEAD: CARMEN PLAPCIANU
E-mail : [email protected]
Tel : (+4021) 493 01 95
Fax : (+4021) 493 02 67
RESEARCH TEAM: 2
Carmen PLAPCIANU
Cristina VALSANGIACOM
researcher
1.The synthesis of perovskite type oxides and the influence of main parameters: pH, molar ratio,
temperature and sintering astmosphere in Sr2FeMoO6, Sr2FeMo1-xWx O6 and La1-x SrxMnO3
compounds.
2.The characterization of Mn+ -STA systems (where Mn+-metallic ion and STA-surfactant) by
elemental chemical analysis, TDA, IR spectroscopy, XRD, Mössbauer spectroscopy and SEM
1.G.Aldica, C.Plapcianu, P. Badica, C.Valsangiacom, B. Poperscu, ”The magnetic effects in
Sr2FeMo6 perovskite type compound obtained by soft chemistry”, J. .Optoelectron.Adv.Mater., 8
(2), 461-463, 2006.
CONFERENCES :
1.C.Plapcianu, G.Aldica, C.Valsangiacom, “Mikrokinetic analysis as tool for evaluation on
nanostructured oxidic catalysts”, Workshop 3 Berlin, Germania, 17-18 September 2005, with
poster “ On the preparing kinetics for precursors of nanostructured perovskites”
32
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_
2.G.Aldica, C.Plapcianu, P.Badica, C.Valsangiacom, B.Popescu,”The magnetic effects on
Sr2FeMoO6 perovskite type compounds obtained by different route”, The 4th National Conference
“ New Research trends in Material Science 2005 ARM-4”, poster
3.E.Volceanov, A.Volceanov, S.Stoleriu, A.Melinescu, C.Plapcianu, C.Valsangiacom,
S.Motoc, R.Neagu, “Influence of twin cations on zirconia composites stability”,ECerS, 19-23
June 2005, Portoroz, Slovenia, 9th European Ceramics Society Conference
4.E.Volceanov, A.Volceanov, S.Stoleriu, S.Motoc, C.Plapcianu, M.Becherescu, “Influence of
Ca2+ and Mg2+ as twinned ions on zirconia powders stability”, The 4th National Conference
“New Research trends in Material Science 2005 ARM-4”
33
Laboratory of Low-Dimensional Systems
____________________________________________________________________________________________
HEAD: Dr. MAGDALENA LIDIA CIUREA
Tel: (+4021) 493 01 95
Fax: (+4021) 493 02 67
TOTAL EMPLOYEES: 42
RESEARCH TEAM: 34
The laboratory contains 6 distinct groups
A.GROUP OF THEORETICAL PHYSICS: CONDENSED MATTER
HEAD: Dr. ALEXANDRU ALDEA
Tel: (+4021) 493 01 95
Fax: (+4021) 493 02 67
RESEARCH TEAM: 7
Dr. Alexandru ALDEA
Dr. Andrei MANOLESCU *
Dr. Paul GARTNER **
Dr. Marian NITA
Dr.Valeriu MOLDOVEANU
Ph.D.cand. Ion-Viorel DINU
Ph.D.cand. Mugurel TOLEA
senior researcher I
senior researcher I
researcher
* Present address: Science Institute, University of Iceland, Dunhaga 3, IS-107 Reykjavik, Iceland
e-mail: [email protected]
** Present address: Institute for Theoretical Physics, University of Bremen, 28334 Bremen,
Germany
Mesoscopic systems. Quantum transport: charge and spin effects. Time dependent transport and
optical effects
Disorder and interaction effects on the orbital and spin magnetization in meso-systems
Mathematical aspects of mesoscopic transport
Quantum interference and correlations in mesoscopic systems: Fano and Kondo effects
1.Study of spin magnetoconductance in the mesoscopic spin-interferometer
2.Resonant and coherent transport through Aharonov-Bohm interferometers with coupled
quantum dots. Transport through quantum rings, Fano regime
33
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3.Research in the field of net current generation in mesoscopic rings and modelling of
dynamical evolution
4.Mathematical development of Landauer Buttiker transport formula
5.Optical effects in quantum dot systems: Coulomb scattering in nitride-based self-assembled
quantum dot systems, correlated photon-pair emission from a charged single quantum dot,
polarons in semiconductor quantum dots and their role in the quantum kinetics of carrier
relaxation
Agreement on joint scientific research,”Charge and spin effects in confined electron systems”,
Univ. Bilkent, Ankara, Turkey
Agreement on joint scientific research,”Electrical and optical properties of semiconductor
heterostructures”, Instituto de Ciencia de Materiales , Madrid, Spain
Scientific colaboration with Inst. fuer Theoretische Physik, Univ. Koeln, ”Mesoscopic Physics”
Scientific colaboration with Univ. Rejkyavik,”Magnetism and dynamic phenomena in mesophysics”
1.A.Aldea, M.Tolea, J.Zittartz, “Spin magnetoconductance in the mesoscopic spininterferometer”, Physica E 28, 191, 2005
2.V.Moldoveanu, M.Tolea, A.Aldea, B.Tanatar, “Resonant and coherent transport through
Aharonov-Bohm interferometers with coupled quantum dots”, Phys. Rev. B 71 125338, 2005
3.S.S.Gylfadottir, M.Nita, V.Gudmundsson, A.Manolescu, “Net current generation in a 1D
quantum ring at zero magnetic field”, Physica E 27, 278, 2005
4.V.Gudmundsson, Y.Y.Lin, C.S.Tang, V.Moldoveanu, J.H.Bardarson, A.Manolescu,
“Transport through a quantum ring, dot, and barrier embedded in a nanowire in magnetic
field”, Phys. Rev. B 71, 235302, 2005
5.T.R.Nielsen, P.Gartner, M.Lorke, J.Seebeck, F.Jahnke, “Coulomb scattering in nitride-based
self-assembled quantum dot systems”, Phys. Rev. B 72, 235311, 2005
6.V.Moldoveanu, M.Tolea, V.Gudmundsson, A.Manolescu, “Fano regime of one-dot
Aharonov-Bohm interferometers”, Phys. Rev. B 72, 085338, 2005
7.H.D.Cornean, A.Jensen, V.Moldoveanu, “A rigorous proof of the Landauer-Buttiker
formula”, J.Math. Phys., 46 042106, 2005
8.F.Bentosela, P.Duclos, V.Moldoveanu, G.Nenciu, “The dynamics of 1D Bloch electrons in
constant electric fields”, J. Math. Phys., 46 043505, 2005
34
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9.S.M.Ulrich, M.Benyoucef, P.Michler, N.Baer, P.Gartner, F.Jahnke, M.Schwab, H.Kurtze,
M.Bayer, S.Fafard, Z.Wasilewski, A.Forchel, “Correlated photon-pair emission from a charged
single quantum dot”, Phys. Rev. B 71, 235328, 2005
10.J.Seebeck, T.R.Nielsen, P.Gartner, F.Jahnke, “Polarons in semiconductor quantum dots and
their role in the quantum kinetics of carrier relaxation”, Phys. Rev. B 71, 125327, 2005
CONFERENCES:
1.V.Moldoveanu, A.Aldea, M.Tolea, “Transport and interaction in disordered systems”, Fano
interference in mesoscopic rings with quantum dots (Int. Conf.TIDS11, Egmond an Zee, Olanda,
aug. 2005, phys.stat.sol(c), vol.3. p.292, 2006
2.A.Aldea, M.Tolea, V.Dinu, "Spin-Flip effects in the AB oscillations", Manipulating Quantum
Coherence in Solid State Systems Cluj (Romania) 29 August- 8 September 2005
3.M.Tolea , B.R.Bulka, "Transport through a Quantum Dot with a magnetic impurity Equation of motion approach", Nanoscale Dynamics and Quantum Coherence MCRTN
International Workshop, Catania (Italy) 2-5 October 2005
4.M.Tolea, B.R.Bulka. "Tunnelling magnetoresistance of a T-shaped Quantum Dot", Physics
of Magnetism" Poznan (Poland) 24-27 June 2005, (to appear in Phys. Stat. Sol. B)
EDUCATIONAL ACTIVITIES:
Ph.D. candidates: V.Dinu, M.Tolea.
B.GROUP OF STRUCTURE AND THIN FILMS
HEAD: Dr. DAN MACOVEI
Tel: (+4021) 493 01 95
Fax: (+4021) 493 02 67
RESEARCH TEAM: 7
Dr. Dan MACOVEI
Dr. Cristian-Mihail TEODORESCU
Dr. Radian POPESCU*
Dr. Florin ZAVALICHE**
Ph.D.cand.Magdalena CONSTANTIN***
Ph.D.cand. Sorin Avram POENARIU****
Ph.D.cand. George Adrian LUNGU
senior researcher I
*
-Temporary address: Max Planck Institute for Microstructure Physics, Halle, Germany
-Temporary address: University of California, Berkeley, USA
***
-Temporary address: University of Maryland, College Park, Baltimore, USA
****
-Temporary address: Ruhr University, Bochum, Germany
**
35
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- Materials for spintronics obtained by associating magnetic metals with semiconductors
- Magnetic interacting nanoparticles
- Rare-earth-fullerene thin films : structure and magnetic properties
- TiO2 thin films and doped TiO2 photocatalysts
- Time of flight and Wien filter cluster mass spectrometry
- Composite materials based on conductive polymers and magnetic nanoparticles
- Zinc ferrites with enhanced capacity of sulfur absorption
1. Setup of a new metal cluster source using adiabatic expansion
2. Influence of deposition parameters (substrate temperature, oxygen pressure) of TiO2 thin
films on their structure and surface stoichiometry
3. Direct comparison of structure, interface reactivity, magnetism and magnetic anisotropy
between Fe/GaAs(100) and Fe/InAs(100)
-Beijing Electron-Positron Collider (BEPC) National Laboratory (Synchrotron Radiation
Facility), Beijing, China
Cooperation Agreement (2003-2007): “Structure investigations by X-ray techniques of new
materials of crystalline, quasicrystalline and disordered structure”.
-Laboratoire de Physique de la Matière Condensée, Université Cergy-Pontoise, France
Cooperation Agreement (2003-2007): “Structure, electronic and magnetic properties of
materials and systems based on combining magnetic metals and semiconductors: metalsemiconductor interfaces, ferromagnetic semiconductors, highly magnetic polarized
semimetals”.
PAPERS PUBLISHED OR ACCEPTED FOR PUBLICATIONS IN 2005:
1.M.Izquierdo, M.E.Dávila, J.Avila, H.Ascolani, C.M.Teodorescu, M.G.Martin, N.Franco,
J.Chrost, A.Arranz, M.C.Asensio, “Epitaxy and magnetic properties of surfactant-mediated
growth of bcc cobalt”, Phys. Rev. Lett. 94, p.187601 (1-4), 2005
2.M.Gartner, A.Ghita, M.Anastasescu, P.Osiceanu, G.Dobrescu, M.Zaharescu, D.Macovei,
M.Modreanu, C.Trapalis, G.Kordas, “Influence of Cu on the morphological and chemical
properties of nanostructured TiO2 films”, J.Optoelectron.Adv.Mater. 7, 401, 2005
3.D.Luca, D.Macovei, C.M.Teodorescu, “Characterization of titania thin films prepared by
reactive pulsed-laser ablation”, Surface Science, accepted
36
____________________________________________________________________________________________
4.F.Iacomi, I.Salaoru, N.Apetroaei, A.Vasile, C.M.Teodorescu, D.Macovei, “Physical
characterization of CdMnS nanocrystalline thin films grown by vacuum thermal evaporation”, J.
Optoelectron.Adv.Mater, 8(1), 266-270, 2006.
CONFERENCES:
1.R.Turcu, D.Bica, L.Vekas, N.Aldea, D.Macovei, O.Pana, O.Marinica, M.L.Soran, A.Nan,
R.Grecu, C.Pop,“Hybrid structures based on polypyrrole and magnetic nanoparticles”, 2nd
NANOFUN-POLY Workshop Applications and Nanostructure-Property Relationships, Madrid
(Spain), March 2005
2.R.Turcu, D.Bica, L.Vekas, N.Aldea, D.Macovei, A.Nan, O.Pana, O.Marinica, C.V.L.Pop,
Z.Wu,“Correlations between the synthesis parameters and the properties of polypyrrolemagnetic nanoparticles composites”, E-MRS 2005 Spring Meeting, Strasbourg (France), June
2005
3.O.Pana, C.M.Teodorescu, D.Macovei, R.Turcu, A.Darabont, M.L.Soran, I.Bratu, N.Jumate,
“Synthesis and structural characterization of nanostructured LaCaMnO3 (LCMO) / C60 thin
films composites”, EMRS 2005 Spring Meeting, Strasbourg (France), June 2005
4.F.Iacomi, M.Purica, E.Budianu, D.Macovei,“Effect of doping on the electrical and optical
properties of CdS thin films”, 6th Intern. Balkan Workshop on Applied Physics, Constanta
(Romania), July 2005
5.D.Luca, D.Macovei, C.M.Teodorescu,“Characterization of titania thin films prepared by
reactive pulsed-laser ablation”, Eur. Conf. on Surface Science ECOSS-23, Berlin (Germany),
Sept. 2005
6.C.M.Teodorescu, D.Luca,“Comparative study of magnetism and interface composition in
Fe/GaAs(100) and Fe/InAs(100)”, Eur. Conf. on Surface Science ECOSS-23, Berlin (Germany),
Sept. 2005
7.D.Luca, D.Mardare, F.Iacomi, C.M.Teodorescu,“Hydrophilic properties of doped TiO2 thin
films”, Eur. Conf. on Surface Science ECOSS-23, Berlin (Germany), Sept. 2005
8.F.Iacomi, D.Mardare, D.Luca, I.Rusu, C.M.Teodorescu,“Physical characterization of CdMnS
nanocrystalline thin films grown by vacuum thermal evaporation”, Intern. Workshop on Surface
Physics, Zdroj (Poland), Sept. 2005
9.R.Turcu, A.Darabont, A.Nan, N.Aldea, D.Macovei, D.Bica, L.Vekas, O.Pana, M.L.Soran,
A.A.Koos, L.P.Biro,“New polypyrrole-multi wall carbon nanotubes hybrid materials”, 4th Nat.
Conf. New Research Trends in Materials Science ARM-4, Constanta (Romania), Sept. 2005
published in J. Optoelectron. Adv. Mater. 8(2), 643, 2006.
1. Ph.D. student: Sorin Avram Poenariu (Ruhr University, Faculty of Electrical Engineering and
Information Techniques, Bochum, Germany)
Subject: “Electrical transport in semiconductor nanostructures”
2. Ph.D. student: George Adrian Lungu (National Institute of Materials Physics, Bucharest)
Subject: “Structure and properties of metal-C60 thin films”
37
____________________________________________________________________________________________
C.GROPUP OF THIN FILMS AND QUANTUM STRUCTURES
HEAD: Dr. TOMA STOICA
Tel: (+4021) 493 01 95
Fax: (+4021) 493 02 67
TOTAL EMPLOYEES: 10
RESEARCH TEAM: 8
1.
2.
3.
4.
5.
6.
7.
8.
Dr. Toma STOICA
Dr. Constantin MOROSANU
Dr. Tionica STOICA
Dr. Mihail LEPSA
Dr. Paul Nicolae RACEC
Ph.D.cand. Adrian SLAV
Sorina Gaman, M. Sc.
George Stan, M. Sc.
senior researcher I
temporary assistant
temporary assistant
-Growth and optoelectric properties of SiGe, GaN and InN nanostructures;
-Experimental investigation of quantum transport in nano resonant tunneling semiconductor
structures;
-Electronic transport theory of semiconductor nanostructures;
-Wide-gap semiconductor thin films and nanostructures obtained by sol-gel procedures;
-Bioactive and hemocompatible ceramic thin films: graded HA structures with high values of
adherence; hemocompatible carbon structures onto titanium substrates
MAIN SCIENTIFIC RESULTS OBTAINED IN 2005
1.Properties of GaN and InN nanowires obtained by MBE growth
2.Top down processing and electrical characterization of resonant tunneling nanostructures
from GaAs /AlGaAs
3.Self-consistent quantum mechanical modeling of Si/SiGe double barrier resonant tunneling
diodes
4.Modeling of ballistic transport in nanoMOSFETs in Landauer-Büttiker formalism
5.Optical and structural characterizations of nanostructured multilayers transparent ITO sol-gel
films deposited onto silicon substrates
6.Bioactive HA surfaces which promote the proliferation of various cell cultures for future in
vivo-tests
7.Hemocompatible DLC coatings onto silicon substrates with long time coagulation times
38
____________________________________________________________________________________________
- Aveiro University, Aveiro, Portugal
Bilateral Cooperation Agreement (2004-2005): "Study of chemical growth process in
physiological media onto calcium phosphate based layers sputtered on various biocompatible
substrates"
- AF Ioffe Institute, St. Petersburg, Rusia
Bilateral Cooperation Agreement (2004-2005): "Doped and undoped carbon films"
- Universitatea Ioannina, Grecia
Bilateral Cooperation Agreement (2006-2007): “Development and evaluation of bioactive
multilayer implants from ceramic coated titanium for tissue engineering applications”
1.T.Stoica, R.Meijers, R.Calarco, T.Richter, H.Lueth, “MBE growth optimization of InN
nanowires”, accepted for publication in J. Crystal Growth
2.L.Vescan, T.Stoica, E.Sutter, “Structural and luminescence properties of ordered Ge islands
on patterned substrates”, chapter in “Lateral alignment of epitaxial quantum dots”, Editor O.G.
Schmidt, to be published as a volume of the Springer Series on Nanoscience and Technology
3.R.Meijers, T.Richter, R.Calarco, T.Stoica, H..P.Bochem, M.Marso, H.Lueth, “GaNnanowhiskers: MBE-growth conditions and optical properties”, accepted for publication in J.
Crystal Growth
4.R.Calarco, M.Marso, T.Richter, A.I.Aykanat, R.Meijers, A. v.d. Hart, T.Stoica, H.Lueth,
“Size-dependent photoconductivity in MBE-grown GaN-nanowires”, Nano Letters 5, 981, 2005
5.R.Calarco, R.Meijers, T.Stoica, H.Lüth, “Piezoresponse force microscopy for imaging of GaN
surfaces”, Phys. Stat. Sol. a, 202, 785, 2005
6.S.Montanari, A.Förster, M.I.Lepsa, H.Lüth, “High frequency investigation of graded gap
injectors for GaAs Gunn diodes”, Solid-State Electronics, 49, 245, 2005
7.J.Wensorra, K.M.Indlekofer, M.I.Lepsa, A.Förster, H.Lüth, “Resonant tunneling in
nanocolumns improved by quantum collimation”, Nano Letters, 5, 2470, 2005
8.G.A.Nemnes, U.Wulf, P.N.Racec, "Non-linear I-V characteristics of nano-transistors in the
Landauer-Büttiker formalism", J. Appl. Phys. 98, 084308, 2005
9.P.N.Racec, U.Wulf, "Quantum theory for ac-admittance", article in press, Materials Science
and Engineering C
10.P.N.Racec, U.Wulf, "Small-signal circuit elements of MIS-type nanostructures", accepted for
publication, Solid State Phenomena (Trans Tech Publications Ltd)
39
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11.T.F.Stoica, M.Gartner, T.Stoica, M.Losurdo, V.S.Teodorescu, M.G.Blanchin, M.Zaharescu,
“Properties of high-porosity sol-gel derived indium-tin oxide films”, J.Optoelectron.Adv.Mater.
vol. 7, 2353, 2005
CONFERENCES:
1.T.Richter, R.Meijers, N.Thillosen, R.Calarco, T.Stoica, H.Lüth, “Epitaxial growth and
structural characterization of GaN nanowhiskers”, Scuola Ereus, 2005
2.R.Calarco, R.Meijers, T.Richter, A.I.Aykanat, T.Stoica, M.Marso, H.Lüth, “Electrical
Transport in GaN-whiskers, DPG 2005, Berlin
3.T.Richter, R.Meijers, R.Calarco, T.Stoica, H.Lüth, “GaN nanowhiskers: epitaxial growth”,
ICNS-6 2005, Bremen
4.R.Meijers, R.Calarco, M.Marso, T.Richter, A.v.d. Hart, T.Stoica, H.Lüth, “GaN
nanowhiskers: epitaxial growth & electrical transport”, ICNS-6 2005, Bremen
5.J.Wensorra, M.I.Lepsa, K.M.Indlekofer, A.Förster, H.Lüth, “Vertical resonant tunneling
diodes in the sub-100 nm range”, Nanoelectronics Days 2005, 09.02.2005 - 11.02.2005,
Forschungszentrum Jülich, Jülich, Germany
6.J.Wensorra, M.I.Lepsa, K.M.Indlekofer, A.Förster, H.Lüth, “Fabrication and characterization
of a vertical resonant tunneling diode in the sub-100 nm range”, Frühjahrstagung der Deutschen
Physikalischen Gesellschaft, 04.03.2005 - 09.03.2005, Berlin, Germany
7.J.Wensorra, M.I.Lepsa, K.M.Indlekofer, A.Förster, H.Lüth, “Fabrication and electrical
characterization of GaAs/AlAs resonant tunneling nanocolumns with lateral dimensions in the
sub-100nm range”, Joint Meeting of the German and the Polish Vacuum Society, 26.10.2005 29.10.2005, Krakow, Poland
8.T.F.Stoica, M.Gartner, M.Losurdo, V.S.Teodorescu, M.G.Blanchin, T.A.Stoica, M.Zaharescu,
„Nano-porosity of indium-thin oxide films obtained by sol-gel method and its effect on optical
and conductive properties”, Second International Workshop on Amorph. Nanostructured
Chalcogen., Sinaia, June20-24,2005
9.P.N.Racec, U.Wulf, "Quantum theory for ac-admittance", contributed talk, E-MRS Spring
Meeting 2005, Symposium A, 31 May - 3 June 2005, Strasbourg (France)
10.U.Wulf, P.N.Racec, "Quantum theory for ac-admittance", contributed talk, China
International Conference on Nanoscience & Technology, China NANO 2005, 9 - 11 June 2005,
Beijing (China)
11.P.N.Racec, E.R.Racec, U.Wulf, Research Tutorial "Resonant transport in semiconductor
quantum structures", Weierstrass Institute for Applied Analysis and Stochastics WIAS, Berlin,
September 24, 2005
12.P.N.Racec, E.R.Racec, U.Wulf, G.Kissinger, H.Richter, "Si/SiGe double barrier resonant
tunneling diodes", contributed talk, 1st Leibniz Conference of Advanced Science NANOSCIENCE 2005 - 06.-08. October 2005, Lichtenwalde (Sachsen), Germany
40
____________________________________________________________________________________________
13.P.N.Racec, U.Wulf, "Admittance of quantum MIS (metal-insulator-semiconductor)-type
structures", contributed talk, DPG Annual Meeting 2005, 4-9 March 2005, Berlin, Germany,
Verhandl. DPG(VI) 40, 251, 2005
14.T.F.Stoica,C.Morosanu, T.Stoica.”Biocompatible structures obtained by sol-gel and
magnetron sputtering”, Second International Workshop on Amorphous and Nanostructured
Chalcogenides, Sinaia, June 20-24, 2005
1. Ph.D. candidate: Adrian Slav
D.GROUP OF SILICON-BASED MICRO- AND NANOSYSTEMS
HEAD: Dr. MAGDALENA LIDIA CIUREA
Tel: (+4021) 493 01 95
Fax:(+4021) 493 02 67
RESEARCH TEAM: 6
Dr. Magdalena Lidia CIUREA,
Dr. Sorina LAZANU,
Dr. Mariana LAZAR KLEIN*
Ph.D.cand. Mihai DRAGHICI**
Ph.D.cand. Lucian JDIRA***
Ph.D.cand. Ionel STAVARACHE,
senior researcher I
researcher
*
Temporary address: University of Wisconsin Madison, Department of Physics,USA
Temporary address: Ruhr Universität Bochum, Germany
***
Temporary address: Research Institute for Molecules and Materials, Nijmegen
University, Holand
**
-Quantum phenomena in silicon-based nanomaterials and nanostructures: experimental and
modeling
-Electronic processes related to defects in silicon-based nanomaterials: experimental and
simulation
-Physics of semiconductors in radiation fields: defect formation and kinetics, role of impurities in
the radiation hardness, stability of defects, influence of irradiation and storage conditions
41
____________________________________________________________________________________________
1. Study of electronic transport mechanisms in Si/SiO2 nanocomposite film
The transport inside nanodots and between them is analyzed.The electronic state energies and the
mean nanodot diameter of 5.2 nm, evaluated by means of a simple quantum well model, are in
good agreement with experimental results and microstructure investigations.
2. The influence of quantum confinement on the visible range photoluminescence in
nanocrystalline porous silicon
3. Explanation of the discrepancies between model calculations and experimental data for
macroscopic detector characteristics (leakage current and effective carrier concentration) after
lepton and hadron irradiation based on the contribution of primary defects. Predictions of the
time degradation of silicon detectors in the radiation environments expected in the LHC
machine upgrade in luminosity and energy
- CERN RD50 Collaboration “Radiation Hard Semiconductors for very high luminosity
colliders” http://cern.ch/rd50.
- Bilateral collaboration between the University of Florence and NIMP in the field of radiation
effects on semiconductor materials (2003 – 2005)
1.M.L.Ciurea, “Quantum confinement in nanocrystalline silicon”, J. Optoelectron. Adv. Mater.
7(5), 2341-2346, 2005
2.M.L.Ciurea, “Electrical properties of nanocrystalline silicon”, J.Optoelectron. Adv. Mater., 8
(1), 13-19, 2006.
3.O.Pana, L.M.Giurgiu, Al.Darabont, V.Iancu, M.L.Ciurea, M.N.Grecu, A.Bot, “Core- shell
effects in granular perovskite manganites”, J. Physics and Chemistry of Solids, in press
4.I.Lazanu, S.Lazanu, “Scenarios about the long-time damage of silicon as material and
detectors operating beyond LHC collider conditions”, Physica Scripta 71, 31, 2005
5.M.Bruzzi, …., S.Lazanu,…(RD-50 Collab.), “Radiation-hard semiconductor detectors for
Super-LHC” Nucl.Instrum.Meth.A541:189-201, 2005
6.M.Moll, …., S.Lazanu, ... et al. (RD-50 Collab.), “Development of radiation tolerant
semiconductor detectors for the Super-LHC”, Nucl.Instrum.Meth A, 546, 99-107, 2005
7.F.Fretwurst, ..S.Lazanu,.. et al. (RD-50 Collab. ); “Recent advancements in the development of
radiation hard semiconductor” Nucl.Instrum.Meth A 552, 7-19, 2005
42
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8.I.Lazanu, S.Lazanu, “Silicon detectors: from radiation hard devices operating beyond LHC
conditions to characterization of primary fourfold coordinated vacancy defects”,
Rom.Rep.Phys.57:342-348, 2005
9.I.Lazanu, S.Lazanu, Chapter: “Silicon detectors for high energy physics: physical models and
predictions for degradation in radiation fields” in: “Progress in experimental high energy
physics”, Nova Publisher, New York, USA, 2005
CONFERENCES:
1.I.Stavarache, M.L.Ciurea, V.Iancu, “Quantum confinement in the photoluminescence of
nanocrystalline porous silicon”, Proc. IEEE CN 00TH8818, Int. Semicond. Conf. CAS 2005,
Sinaia, 3 – 5 Oct. 2005, 1, 55 – 58, 2005
2.M.L.Ciurea, “Quantum transport in nanocrystalline semiconductors” (invited paper), Proc. 3rd Int. Conf. Powder Metallurgy RoPM 2005, Sinaia 7-9 July 2005, 1, 123-136, 2005
3.M.L.Ciurea, “Quantum effects in silicon nanodots” (invited paper), 4-th Isotopic and
Molecular Processes, Cluj-Napoca 22-24 Sept 2005, to be published in Studia Universitatis
Babes-Bolyai, Physica, special issue, 2005
4.M.L.Ciurea, “Quantum confinement in nanocrystalline silicon” (invited paper), 2-nd
Workshop Amorphous and Nanostructured Chalcogenides, Sinaia 19-24 June 2005,
J.Optoelectron. Adv. Mater. 7(5), 2341-2346, 2005
5.I.Stavarache, V.Iancu, M.L.Ciurea, “Effect of quantum confinement on photoluminescence in
nanocrystalline silicon”, Proc. 4-th National Conf. “New Research Trends in Material Science
ARM-4” Constanta 4-6 Sept. 2005 1, 934-937, 2005
6.V.S.Teodorescu, I.Stavarache, M.L.Ciurea, V.Iancu “Correlation between microstructure
and transport in silicon nanodots” National Conf. of Physics, Bucharest, 13- 16 Sept. 2005
7.M.L.Ciurea, “Specific properties of nanostructured silicon systems” (invited lecture), First
Symposium on Technical Physics and Physical Engineering, Bucharest, 13-14 Sept. 2005
8.I.Lazanu, S.Lazanu, “An analysis of the expected degradation of silicon detectors in the future
ultra high energy facilities”, Proc. 9th ICATPP Conference on Astroparticle, Particle, Space
Physics, Detectors and Medical Physics Applications, Villa Olmo, 17-21 October, 2005, Word
Publishing, accepted
9.S.Lazanu, I.Lazanu “Time dependence of the behaviour of silicon detectors in intense
radiation fields and the role of primary point defects”, 7-th Int. Conf. on Position Sensitive
detectors, Liverpool, U.K., September 2005
10.S.Lazanu, I.Lazanu, M.L.Ciurea, I.Stavarache, “Influence of primary defects on the
radiation Hardness of silicon detectors”, 12th International Conference of Nonconventional
Technologies, Bucharest, Nov. 2-4, 2005 , Nonconventional Technologies Review 4, 69, 2005
11.RD-50 Collab. …., S. Lazanu,…” Recent results from RD50”, Vertex 2005 November 7 11, 2005 Chuzenji Lake, Nikko, Japan
43
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12.RD-50 Collab. …., S. Lazanu, “Development of radiation tolerant silicon detectors for the
SLHC”, 7th International Conference on Large Scale Applications and Radiation Hardness of
Semiconductor Detectors, Florence, Italy, 5-7 October 2005
13.RD-50 Collab. …., S. Lazanu, “Radiation tolerant semiconductor sensors for tracking
detectors", TIME05 – Workshop on Tracking In high Multiplicity Environments Zürich,
Switzerland 3-7 October 2005
Ph.D. candidates: Mihai Draghici, Lucian Jdira, Ionel Stavarache
E.GROUP OF GAS SENSORS
HEAD: ADELINA TOMESCU
Tel: (+4021) 493 01 95
Fax:(+4021) 493 02 67
RESEARCH TEAM: 6
1. Ph.D.cand. Adelina Tomescu
2. Dr. Nicolae Barsan
3. Dr. Alexandru Oprea
4. Ph.D.cand. Razvan Mihai Roescu
5. Ph.D.cand. Irina Dumitriu
6. Cristian Simion
senior researcher I
temporary assistant
- Gas sensors based on thin layer films of metal oxides: SnO, SnO2, ZnO, Fe2O3, NiO, InOx,
SnO2-PdO.
- Complex characterisation by optical and structural investigations of some materials tested as
gas detectors (best functional conditions, selectivity, response speed, stability, duration of life) by
electrical measurements (electrical resistance and work function).
- Development of low cost and low power consumption devices (sensors tailored for industrial
process control, environmental monitoring and civil protection applications) based on the
prepared micro and nano-structured materials deposited on ceramic substrates.
1.Obtaining of an experimental model of Metal Oxide Semiconductor sensor for selective
detection of CO and CH4 by tuning of temperature of active layer through the built-in heater
44
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2.Complex investigations of MOS sensors by means of simultaneous monitoring of two physical
parameters: conductance (resistance) along with work function variations ∆Φ, thermal effect ΔT
and catalytic combustion
3.Elaboration of an evaluation procedure for gas sensors used in environmental monitoring
applications
4.An evaluation procedure for the gas sensors involves an experimental measurement stand and
methods which are required for a complet characterisation of the parameters which describe the
functionality of sensors, in direct relation with the possibilities of the experimental stand: signal
S, partial sensitivity m, analitical sensitivity γ, low detection limit LDL, response time/recovery
time, selectivity mij, drift D, stability ζ, reproducibility Q
- Scientific Cooperation Agreement with the Gas Sensors Research Group at the Institut fuer
Physikalische und Theoretische Chemie, Eberhard Karls Universitaet Tuebingen, GERMANY.
A.Tomescu, R.Roescu, “Electron affinity changes induced by gaseous species present in the
surrounding atmosphere ”, J.Optoelectron.Adv.Mater., vol. 7, No.3, 1529-1533, 2005
CONFERENCES:
1.A.Tomescu, R.Roescu, C.E.Simion, “Gas detection based on surface reactivity of metal
oxide semiconductors“, Proceedings of ICNcT 2005 (International Conference of
Nonconventional Technologies), 101-104
2.A.Tomescu, M.Bercu, R.Roescu, C.Moldovan, “Temperature dependence of CO detection by
SnO2: Pd sensitive films gas sensors”, Proceedings of CAS’2005 (International Semiconductor
Conference), 193-196
Ph.D. candidates: Adelina Tomescu, Razvan Mihai Roescu, Irina Dumitriu.
F.GROUP OF X-RAY DIFFRACTION, LB FILMS
AND COMPUTER-ASSISTED MODELLING OF AMORPHOUS SOLIDS
HEAD: Dr. MIHAI A. POPESCU (S. R. Ovshinsky Prize, 2004)
Tel: (+4021) 493 01 95
Fax:(+4021) 493 02 67
45
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RESEARCH TEAM: 4
1. Dr. Mihai A. Popescu
(S. R. Ovshinsky Prize for Excellence in Non-Crystalline
Chalcogenides, 2004) senior researcher I
2. Dr. Adam Lörinczi
3. Dr. Mihaela Catalina Stegarescu
researcher
4. Florinel Sava
researcher
- Amorphous and disordered solids
- Phase-change materials
- Modeling of nanostructures and of amorphous structures (chalcogenides)
- Chalcogenides alloys and photo-structural transformations
- Thin amorphous PLD films based on piezoelectric and luminescent materials
- Chalcogenide materials for sensors (gas and heavy ions in water)
- Langmuir-Blodgett films
1.Thin films deposited by PLD based on metal-chalcogenide material
Tin-selenium materials have been prepared as solid targets for the preparation of thin films by
pulsed laser deposition (PLD). The films were studied by X-ray diffraction and high resolution
microscopy. The structure and properties of the films were investigated. The gas and vapour
sensing effect was tested with promising results.
2.Atomic scale modelling of mixed carbon nano-configurations: fullerene-nanotubules
Several models of nanotubule-fullerene configurations have been developed and their structures
at the atomic scale were got by energy relaxation. It was concluded that the mixed configuration
corresponding to the attachment of a fullerene molecule C60 to a nanotubule of carbon is stable.
Therefore such combinations useful for making the connections in nano-devices are possible and,
therefore, can be realized.
3.Structural modeling of GeSb2Te7 switching glass; Crystalline-glass transition
A new model of crystalline-amorphous transition based on closed clusters has been developed.
- Bilateral cooperation program Romania (Bucharest) – Ukraine (Lviv). Program:
“Semiconducting chalcogenide glasses, nano-structured materials and other complex
materials”, NIMP-Bucharest - Lviv Scientific Research Institute of Materials of Scientific
Research Company “Carat”
46
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- Bilateral cooperation program Romania (Bucharest) – Germany (Chemnitz). Program: “Noncrystalline and crystalline semiconductors and complex oxides doped by rare-earth elements
prepared as thin films”, NIMP-Bucharest - Technical University Chemnitz, Germany
- Indo-Romanian research cooperation in Science and Technology: “Optical and complementary
researches on new chalcogenide glasses”: NIMP-Bucharest, – Indian Institute of Science,
Bangalore, India
- Bilateral cooperation program Romania (Bucharest) – Ukraine (Kiev). Program: “Development
of high-resolution inorganic photoresists”, NIMP-Bucharest - V.E. Lashkaryov Institute of
Semiconductor Physics-Kiev
1.W.Hoyer, R.Kleinhempel, A.Lőrinczi, A.Pohlers, M.Popescu, F.Sava, “Interstitial void
structure in Cu-Sn alloy as revealed from RMC modelling”, Journal of Physics: Condensed
Matter, 17(5) s31-s36, 2005
2.M.Popescu, F.Sava, A.Lőrinczi, D.Savastru, S.Miclos, R.Savastru, “Microspheres,
planoconvex microlenses and optical fibres based on glassy As2S3”, J.Optoelectron.Adv.Mater.,
7(2), 1103-1106, 2005
3.M.Popescu, F.Sava, A.Lőrinczi, M.Stegarescu, S.Georgescu, I.N.Mihailescu, G.Socol,
D.Stanoi, L.Daroczi, A.Kokenyesi, M.Leonovici, D.Wagner, “Preparation and properties of
langasite and YAG amorphous films”, J.Optoelectron.Adv.Mater., 7(2), 963-966, 2005
4.M.S.Iovu, E.I.Kamitsos, C.P.E.Varsamis, P.Boolchand, M.Popescu “Raman spectra of
AsxSe100-x glasses doped with metals”, J.Optoelectron.Adv.Mater., 7(3), 1217-1221, 2005
5.M.Popescu, F.Sava, A.Anghel, A.Lőrinczi, I.Kaban, W.Hoyer, “Phase-change ovonic
switching. A modelling investigation of the structural transition”, J.Optoelectron.Adv.Mater., 7
(4), 1743-1748, 2005
6.M.Popescu, F.Sava, N.Aldea, X.Yaning, H.Tiandou, L.Tao, M.Leonovici, “X-ray absorption
near edge structure of As2Se3 and As4Se4 thin amorphous films”, J.Optoelectron.Adv.Mater., 7
(4), 1801-1806, 2005
7.F.Sava, A.Anghel, I.Kaban, W.Hoyer, M.Popescu “Atomic scale structure of Ge30As4S66” J.
Optoelectron.Adv.Mater., 7(4), 1971-1975, 2005
8.S.Zamfira, M.Popescu, F.Sava “Fullerene and nanotubes based on arsenic networks. A
modelling study”, J.Optoelectron.Adv.Mater., 7(4), 2029-2034, 2005
9.M.Popescu, “Disordered chalcogenide optoelectronic materials:
applications”, J.Optoelectron.Adv.Mater., 7(4), 2189-2210, 2005
phenomena
and
10.M.S.Iovu, V.G.Ciorba, E.P.Colomeico, M.A.Iovu, A.M.Nastase, A.Prisacari, M.Popescu,
O.I.Shpotyuk, “Optical photoinduced phenomena and holographic recording in amorphous AsSe thin films” J.Optoelectron.Adv.Mater., 7(5), 2333-2339, 2005
47
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11.A.Lőrinczi, F.Sava, “Cluster model of As2S3 glass”, Chalcogenide Letters, 2(1), Jan. 2005
(http://www.chalcogen.infim.ro/letters.html)
12.F.Sava, A.Anghel, I.Kaban, W.Hoyer, M.Popescu, “Atomic scale structure of Ge30As4S66“,
Chalcogenide Letters, vol.2, No.6, June 2005 (http://www.chalcogen.infim.ro/letters.html)
13.S.Zamfira, M.Popescu, F.Sava, “Fullerene-like and nanotubes based on arsenic networks. A
modelling study”, Chalcogenide Letters, vol.2, No.6, June 2005, (http://www. chalcogen. infim.
ro/letters.html)
14.M.Popescu, F.Sava, N.Aldea, X.Yaning, H.Tiandou, L.Tao, M.Leonovici, "XANES in
amorpohous halcogenide filmas based on As-S.", Chalcogenide Letters, vol.2, No.7, July 2005
(http://www.chalcogen.infim.ro/letters.html)
15.M.Popescu, "Medium range order in non-crystalline materials", Journal of Ovonic Research,
vol. 1, No. 1, February 2005 (http://www.chalcogen.infim.ro/viitor.html)
16.M.Popescu, F.Sava, A.Anghel, A.Lőrinczi, I.Kaban, W.Hoyer, M.S.Iovu, "Structural
transition in phase-change ovonic switching", Journal of Ovonic Research, vol.1, No. 4, August
2005, (http://www.chalcogen.infim.ro/viitor.html)
17.M.Popescu, "Ovonic materials", Journal of Ovonic Research, 1 (6), December 2005
(http://www.chalcogen.infim.ro/viitor.html)
18.V. Babin, M. Popescu, M. Ciobanu, N. D. Nicolae, C. Talianu, G. Ciuciu, “Model of the
interband nonlinear absorption in amorphous chalcogenides: Quasi-linear analytical solutions”
accepted for J. Mater. Sci. E: Materials in Electronics
CONFERENCES:
1.M.Popescu, “Chalcogenides: past, present, future” (Invited Lecture), Internat. Conf. on
Amorph. and Nanost. Semic. ICANS-21, Lisbon Sept. 2005
2.M.Popescu, F.Sava, A.Lorinczi, “Self-organization and anisotropy in amorphous
chalcogenides” Internat. Conf. on Amorph. and Nanost. Semic. ICANS-21, Lisbon Sept. 2005
3. M. Popescu, F. Sava, A. Lőrinczi, “Intermediate phase in non-crystalline chalcogenides”,
Intern. Conf. CO-MAT-TECH – 2005, Trnava, Slovakia, 20-21 October 2005.
PhD students: Paul Barvinski, Coman Aurel, Calin Moise, Razvan Roescu
48
Laboratory of Optics and Spectroscopy
________________________________________________________________________________________________
HEAD: Dr. MIHAELA BAIBARAC
E-mail:[email protected]
Tel: (+4021) 493 01 95
Fax: (+4021) 493 02 67
TOTAL EMPLOYEES: 35
RESEARCH TEAM: 27
A.GROUP OF OPTICS
HEAD: Dr. IOAN BALTOG
Tel: (+4021) 493 01 95
Fax:(+4021) 493 02 67
RESEARCH TEAM: 7
1.
2.
3.
4.
5.
6.
7.
Dr. Ioan BALTOG
Dr. Mihaela BAIBARAC
Lucian MIHUT
Timucin VELULA
Nicoleta PREDA
Marius HUSANU
Edit LENGYEL*
senior researcher I
* Present address: Max-Planck-Institut fur Chemische Physik Fester Stoffe, Lab. High Pressures,
Leipzig, Germany
Synthesis of hybrid organic-inorganic and composite materials based on polymers and various
particles of micrometric and nanometric size and their characterization by studies of Raman
Scattering, Photoluminescence, Photoconductivity and Conductivity.
Materials under investigation: conducting polymers, carbon nanoparticles: fullerene (C60) and
single-walled carbon nanotubes (SWNT), micro and nanoparticles of PbI2, nanostructured composite
and hybrid organic-inorganic materials.
49
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1.Functionalization of single-walled carbon nanotubes with conducting polymers evidenced by
Raman and FTIR spectroscopy
Using Raman scattering and Fourier transformed (FTIR) spectroscopy , on show that the vibrational
properties of single-walled carbon nanotubes (SWNTs) functionalized with conducting polymers
(CPs), such as polyaniline (PANI) and poly (3,4-ethylenedioxythiophene) (PEDOT), are different
depending on the synthesis method. In the case of SWNTs electrochemically functionalized with
PANI , an additional roping of nanotubes with PANI is demonstrated by the increase in intensity of
the Raman band at 178 cm-1 that normally is associated with radial breathing modes of bundled
SWNTs.The functionalization of SWNTswith polymer induces strong steric hindrance effects
observed in FTIR spectra of SWNTs/PANI composites by the enhancement of bands at ca. 740-750
and 772 cm-1 associated to the deformation vibration of the benzoid and quinoid ring, respectively.
2. Electrochemical oxidation of SWNTs in HCl solution
Raman spectroscopy and cyclic voltammetry (CV) are used for the investigation of the oxidationreduction processes of single-wall carbon nanotubes (SWNTs) films in an HCL 0.5M solution. In
the potential ranges of ( +100;+800) and ( 0;+1500) mV vs. saturated calomel electrod (SCE), the
oxidation-reduction reactions of SWNT films in both aqueous and semi-aqueous HCL 0.5M
solutions, are reversible and irreversible, respectively. At potentials higher than +1000mV vs.SCE,
SWNTs break in fragments of different sizes. A post-treatment with an alkaline solution results in a
partial restoration of the SWNTs.
3. Coherent anti-Stokes Raman Scattering on single-walled carbon nanotubes thin films excited
through surface plasmons excitation
Experimental data that indicate an abnormal anti-Stokes Raman emission, reminiscent of Coherent
anti-Stokes Raman Scattering (CARS) are reported. It originates from a wave mixing process
between the incident laser light (ωl) and the Stokes Raman light (ωs) generated by a Surface
Enhanced Raman Scattering (SERS) mechanism. The variation of anti-Stokes SERS spectra of
single-walled carbon nanotubes (SWNTs), copper phthalocyanine (CuPc) and poly(bithiophene)
(PBTh) as a function of the film thickness, the laser excitation intensity and the numerical aperture
of the microscopic objective used for collecting the scattered light demonstrate the described
phenomenon.
4. Mechanico-chemical intercalation of single-walled carbon nanotubes with different host matrices
evidenced by SERS spectrsocopy and photoluminescence
Single-walled carbon nanotubes (SWNTs) under a moderate non-hydrostatic pressure of 0.58 GPa,
undergo a non-reversible transformation. Due to the plastic deformations, structural defects and
carbon nanotube fragments of different size are produced. Short fragments of spherical or ellipsoidal
form, behaving as closed-shell fullerenes are observed both by Raman spectroscopy and
photoluminescence (PL). The main vibrational indicative of the fragments of shorter length is the
band at ~ 1458 cm-1 that is regularly observed in the Raman spectra of fullerene. Similar to
50
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fullerenes self assemblies, the interaction between the nanotube fragments is noticed in the Raman
spectrum by the band at ~ 94 cm-1 that reveals an inter-particle vibration mode.
5. Optical properties of PPV/SWNTs composites
Optical absorption, photoluminescence, Raman scattering spectra of carbon nanotube- poly
(paraphenylene vinylene) (PPV) composite films show that the effect of the low conversion
temperature on all the optical spectra is similar to that of increasing the nanotube concentration in
standard polymer.
6. Self-assembling of C60 fullerene in nanometer size clusters
Self-assemblies of C60 fullerene in binary solvent mixtures (o-dichlorobenzene/acetone and odichlorobenzene/N-methyl-2-pyrrolidinone) produced by weak (van der Waals type) and strong
forces (originating in charge transfer) are featured by different SERS, UV-VIS absorption and
photoluminescence spectra.
7. Optical properties of low-dimensional PbI2 particles intercalated with organic species
By correlated studies of scanning electron microscopy, Raman spectroscopy, optical absorption and
low temperature photoluminescence (PL) we have demonstrate that whichever was the synthesis
procedure for low-dimensional PbI2 particles: cooling to the room temperature a boiling saturated
aqueous PbI2 solution containing polymer or the chemical reaction of KI and Pb(NO3)2 in
acetonitrile, in both cases were identified platelets of PbI2 and rods like particles. The luminescence
and Raman signature of the rods is quite different for the one of the PbI2 platelets. As distinct feature
of the rod-like particles, regardless the method used for their synthesis must be mentioned the same
geometrical form, a very similar Raman spectrum and specific PL emission band centered at ~2.23
eV.
- Bilateral Cooperation Program (2003-2007) with Institut de Matériaux de Nantes, France: Etudes
spectroscopiques et spectroélectrochimiques des materiaux composites ou hybrides a base de
polymères conjugués et composés carbones nanostructures
- Bilateral Cooperation Program (2005-2009) with Materials Science Institute, Barcelona, Spain:
Hybrid materials based on conducting organic polymers (COP) and semiconducting and metallic
nanoparticles – synthesis, characterization and applications
- Partner in a Research Training Networks project entitled: Carbon Nanotube Composites: Towards
Strong, Multifunctional and Biosensitive Nanomaterials and Devices (proposal made in March
2005)
51
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PAPERS PUBLISHED IN 2005 OR ACCEPTED FOR PUBLISHING
1.M.Baibarac, L.Mihut, N.Preda, I.Baltog, J.Y.Mevellec, S.Lefrant, “Surface-enhanced Raman
Scattering studies on C60 fullerene self-assemblies”, Carbon, 43, 1-9, 2005
2.S.Lefrant, M.Baibarac, I.Baltog, T.Velula, J.Y.Mevellec, O.Chauvet, “Electrochemical and
vibration properties of single-walled carbon nanotubes in hydrochloric acid solutions”, Diamond
and Related Materials, 14, 873-880, 2005
3.S.Lefrant, M.Baibarac, I.Baltog, J.Y.Mevellec, C.Godon, O.Chauvet, “Functionalization of
single-walled carbon nanotubes with conducting polymers evidenced by Raman and FTIR
spectroscopy”, Diamond and Related Materials, 14, 867-872, 2005
4.M.Baibarac, I.Baltog, S.Lefrant, C.Godon, J.Y.Mevellec, “Mechano-chemical interaction of
single-walled carbon nanotubes with different host matrices evidenced by SERS spectrocopy”,
Chem. Phys. Lett., 406, 222-227, 2005
5.S.Lefrant, M.Baibarac, I.Baltog, “Surface enhanced Raman scattering studies on chemically
transformed carbon nanotubes thin films”, J. Raman Spectroscopy, 36, 676-698, 2005, review
article
6.I.Baltog, M.Baibarac, S.Lefrant, “Coherent anti-Stokes Raman scattering on single-walled
carbon nanotubes and cooper phtalocyanine thin films excited through surface plasmons”, J. Optics
A: Pure and Applied Optics, 7, 632-639, 2005
7.M.Baibarac, I.Baltog, L.Mihut, N.Preda, T.Velula, C.Godon, J.Y.Mevellec, J.Wery, S.Lefrant,
“Surface enhanced Raman Scattering and photoluminescence studies on single-walled carbon
nanotubes submitted to non-hydrostatic compression”, J.Optoelectron.Adv.Mater., 7, 2173-2181,
2005
8.I.Baltog, L.Mihut, M.Baibarac, N.Preda, T.Velula, S.Lefrant, “Surface enhanced Raman
Scattering, photoluminescence and viscosity studies on C60 aggregates in N-methyl-2pyrrolidinone”, J.Optoelectron.Adv.Mater., 7, 2165-2172, 2005
9*.I.Baltog, M.Baibarac, S.Lefrant, “Coherent anti-Stokes Raman scattering on single-walled
carbon nanotubes thin films excited through surface plasmons”, Phys. Rev. B, 72, 245402-245413,
2005
* ) Paper selected by the American Institute of Physics and the American Physical Society as
covering a focused area of frontier research in Nanoscale Science & Technology. The article
was included in the Virtual Journal of Nanoscale Science & Technology, vol. 19, issue 25,
December 2005.
10.S.Lefrant, M.Baibarac, I.Baltog, C.Godon, J.Y.Mevellec, J.Wery, E.Faulques, L.Mihut,
H.Aarab, O.Chauvet, “SERS, FT-IR and photoluminescence studies on single-walled carbon
nanotubes/conducting polymers composites”, Synth. Met., 155, 666-669, 2005
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11.E.Mulazzi, R.Perego, H.Aarab, L.Mihut, E.Faulques, S.Lefrant, J.Wery, “Optical properties of
carbon nanotube-PPV composites: influence of the PPV conversion temperature and nanotube
concentration”, Synth. Met., 154, 221-224, 2005
12.M.Sima, I.Enculescu, V.Ghiordanescu, L.Mihut, “Absorption and photoluminescence properties
of CdS:Mn2+: Cu+ nanostructures”, J.Optoelectron.Adv.Mater., 7, 1949-1955, 2005
13.I.Baltog, M.Baibarac, L.Mihut, N.Preda, T.Velula, S.Lefrant, “Spectroscopic studies on C60
fullerene solutions in binary solvent mixtures”, Rom.Rep. Phys., 57, 807-814, 2005
14.N.Preda, N.Cobianu, C.Cincu, T.Velula, “The kinetics of styrene polymerization in solution
initiated by redox systems”, U. P. B. Sci. Bull. Series B, 67, 55-62, 2005
15.N.Preda, M.Baibarac, I.Baltog, L.Mihut, T.Velula, C.Cincu, “Viscosity studies on polyanilineC60 composites solutions in N-methyl-2-pyrrolidinon”e, U. P. B. Sci. Bull. Series B, 67, 13-20, 2005
CONFERENCES:
1.S.Lefrant, M.Baibarac, I.Baltog, C.Godon, J.Y.Mevellec, L.Mihut, “Mechanico-chemical
interaction of single-walled carbon nanotubes with different host matrices evidenced by SERS
spectroscopy and photoluminescence”, Microtehnologies for the New Millenium, Sevilla, Spain, 911 May 2005, Proceedigs of SPIE, 5838, 105, 2005
2.M.Baibarac, I.Baltog, T.Velula, J.Y.Mevellec, S.Lefrant, “Electrochemical functionalization of
single-walled carbon nanotubes with polyaniline evidenced by Raman and FTIR spectroscopy, 14th
Romanian International Conference on Chemistry and Chemical Engineering, Bucharest, Romania,
22-24 September 2005, Proceedings RICCCE XIV, 2, S10-99, 2005
3.M.Baibarac, I.Baltog, S.Lefrant, C.Godon, J.Y.Mevellec, “Surface Enhanced Raman Scattering
studies on single-walled carbon nanotubes compressed in different host matrices”, 14th Romanian
International Conference on Chemistry and Chemical Engineering, Bucharest, Romania, 22-24
September 2005, Proceedings RICCCE XIV, 4, S09-103, 2005
4.N.Preda, M.Baibarac, L.Mihut, T.Velula, I.Baltog, S.Lefrant, “Effects of stoichiometric
changes in the chemical synthesis of PbI2 microparticles evidenced by optical methods”, 14th
Romanian International Conference on Chemistry and Chemical Engineering, Bucharest, Romania,
22-24 September 2005, Proceedings RICCCE XIV, 1, S01-110, 2005
5.N.Preda, L.Mihut, I.Baltog, T.Velula, V.Teodorescu, “Optical properties of low-dimensional
PbI2 particles embedded in polyacrylamide matrix”, International Conference on Fundamental and
Applied Research in Physics, Iasi, Romania, 26-29 October 2005, to be published in Journal of
Optoelectronics and Advanced Materials
53
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Dr. M. Baibarac – Postdoc stage, Materials Science Institute, Department of Crystallography and
Solid State Chemistry, Barcelona, Spain
E. Lengyel – PhD student in Physics, Max-Planck-Institut fur Chemische Physik Fester Stoffe, Lab.
High Pressures, Leipzig, Germany
N. Preda – PhD student in Chemistry, University Politehnica of Bucharest, Romania
B.GROUP OF LIQUID CRYSTALS AND SURFACE INTERACTIONS
HEAD: Dr. STEFAN FRUNZA
Tel: (+4021) 493 01 95
Fax: (+4021) 493 02 67
RESEARCH TEAM: 5
1. Dr. Stefan FRUNZA
2. Dr. Ligia FRUNZA
3. Traian BEICA
4. Irina-Ionela ZGURA
5. Dr. Anatoli SERGHEI*
Dr. Rodica MOLDOVAN**
*
**
senior researcher I
senior researcher I
senior researcher I (guest)
Present adress: University of Leipzig, Germany; e-mail [email protected]
Institute of Mathematics "Simion Stoilow" of Romanian Academy, Bucharest
1. Nematic liquid crystals in confinement
Materials under investigation : composites of nematic liquid crystals and aerosil, mesoporous
molecular sieves, different metallic oxides.
2. Alignment properties of polymeric layers
Materials under investigation : nematic liquid crystals; anchoring energy; azimuthal anchoring
energy on the polymer surface; polymer aligning layers.
3. Highly dispersed oxide materials containing metal ions with variable valency
Materials under investigation : microstructured oxide materials, perovskites and ferrites. Salen type
compounds confined to molecular sieves.
54
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1. Nematic liquid crystals in confinement
The molecular dynamics of 4-n-octyl-4'-cyanobiphenyl (8CB) confined to the nanopores of new
SBA-type molecular sieves was investigated in a wide temperature range using broadband dielectric
spectroscopy (10-2 to 109 Hz). One molecular sieve has a hexagonal structure of the pores while the
other is a cellular nanoporous material. To explore the extent of surface interaction effects a high
and a low filling degree were considered.
For the molecular sieves with a high filling degree two relaxation regions were observed: a bulk-like
relaxation process related to molecules, which behave as mesophase, located in the centre of the
pores. The second relaxation process has a much lower relaxation rate than the former and is
assigned to molecules located in a surface layer. The temperature dependence of its relaxation rates
follows the Vogel-Fulcher-Tammann law, characteristic for glassy dynamics.
For samples with a low filling degree only one relaxation process due to the surface layer was
observed. Moreover, especially at the temperatures lower than the melting point of bulk 8CB, its
relaxation rate is situated between the characteristic frequencies of the two relaxation processes
observed for the pores with a high filling degree. This behaviour gives a measure of the extension of
the influence of the wall on the neighbouring 8CB molecules. In addition, the differences revealed
by the molecule dynamics inside the two types of nanoporous materials are related to both surface
interactions and geometrical constraints.
2. Alignment properties of polymeric layers
Alignment properties of rubbed films of polyvinyl imidazole were studied by observing with the
polarizing microscope the features of the nematic liquid crystal (LC) droplets onto these layers. It
was found that the observing of the droplets can reveal the direction of easy axis on the alignment
substrate not only in the case of LC having the director normal to the LC/air interface but also in the
case of the director parallel to this interface, when no disclination line could be seen. We observed
that some of the LCs are oriented parallel to the rubbing direction, but the other LCs are
perpendicularly oriented. This peculiar behavior is at variance to that found on rubbed layers of
polyvinyl alcohol.
3. Highly dispersed oxide materials containing metal ions with variable valency
Perovskites with piezoelectric properties were tested in a test oxidation reaction, under experimental
conditions allowing to these properties to manifest. Influence of the ac field on the catalytic activity
was pursued. The tests were performed in the catalytic decomposition of hydrogen peroxide at room
temperature. Blank experiments were also performed: decomposition of hydrogen peroxide in the
absence of the catalysts; decomposition of hydrogen peroxide in the presence of ac field; reaction in
the presence of the catalyst without ac field. Preliminary results have shown that the conversion is
higher in the presence of the ac field. Careful measurements of the pH have shown its variation
during the reaction. Perovskites and ferrite samples were also tested in methane combustion, total
oxidation of toluene and isobuthane.
55
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-Partener in the EU Project 505834 CONCORDE (tip CA, FP6, NMP Priority 3): "Co-ordination of
Nanostructured Catalytic Oxides Research and Development in Europe", Coordonator: Dr. Vicente
Cortes Corberan [Consejo Superior de Investigaciones Cientificas (ICP.CSIC), Spain];
Resp. NIMP (INCDFM): Dr. Ligia Frunza.
-Bilateral Cooperation "Surface effects in composites systems and guest – host interaction in
restricted geometry" between NIMP (Romania) and Bundesanstalt fuer Materialforschung undpruefung (BAM), Berlin, Germany, 2004-2006.
PUBLISHED PAPERS:
1.L.Frunza, H.Kosslick, I.Pitsch, S.Frunza, A.Schönhals, "Rotational fluctuations of water inside
the nanopores of SBA-type molecular sieves", J. Phys. Chem. B 109, 9154-9159, 2005
2.L.Frunza, I.Zgura, I.Nicolaie, A.Dittmar, H.Kosslick, R.Fricke, "Embedding Jacobsen
manganese(III) salen complex into nanoporous molecular sieves: spectroscopic characterisation of
host-guest interactions", J.Optoelectron.Adv.Mater. 7, 2141 – 2148, 2005
3.S.Frunza, T.Beica, R.Moldovan, I.Zgura, L.Frunza, "Peculiar orientation of nematic liquid
crystals on rubbed polyvinylimidazole", J.Optoelectron.Adv.Mater. 7, 2149 – 2157, 2005
4.L.Frunza, H.Kosslick, S.Frunza, A.Schönhals, "Molecular dynamics of 4-n-octyl-4
´-cyanobiphenyl in partially filled nanoporous SBA-type molecular sieves", Micropor. Mesopor.
Mater. accepted December 2005 (IF=2)
5.A.Serghei, H.Huth, M.Schellenberger, C.Schick, F.Kremer, "Pattern formation in thin
polystyrene films induced by an enhanced mobility in ambient air", Phys. Rev. E, 71, 061801, 2005
6.A.Serghei, Y.Mikhailova, H.Huth, C.Schick, K.J.Eichhorn, B.Voit, F.Kremer, "Molecular
dynamics of hyperbranched polyesters in the confinement of thin films", Eur. Phys. J. E 17, 199,
2005
7.A.Serghei, F.Kremer, "Molecular dynamics in thin polymer film in Fractals, diffusion and
relaxation in disordered complex systems, Adv. Chem. Phys., ed. Stuart A. Rice (guest editors: W.T.
Coffey, Y.P. Kalmykov), John Willey & Sons, Inc., in press 2005
8.T.Beica, R.Moldovan, I.Zgura, S.Frunza, "Improved method to determine the temperature
dependence of the interfacial tension at the interface liquid crystal/isotropic liquid", Proc. Rom.
Acad., Ser. A, submitted November 2005
9.L.Frunza, C.Negrila, C.Miclea, L.Amarandei, A.Dittmar, H.Kosslick, R.Fricke, "Study of
superficial layer of some piezoelectric perovskites", Proc. Rom. Intern. Conf. Chem. Chem. Engn.RICCCE XIV to appear
56
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10.T.Beica, R.Moldovan, I.Zgura, S.Frunza, " Method to study the temperature dependence of the
interfacial tension at the interface liquid crystal/ isotropic liquid ", Proc. Rom. Intern. Conf. Chem.
Chem. Engn.- RICCCE XIV to appear
CONFERENCES:
1.L.Frunza, "Models for the temperature dependence of water dynamics and desorption", 2nd
CONCORDE Workshop "In situ characterization and modelling of oxide catalysts", Belfast,
Northern Ireland, 18-19th February 2005, Invited lecture
2.L.Frunza, S.Frunza, T.Beica, I.Zgura, A.Schönhals, “Surface interactions in composites with
high silica density containing aerosil and cyanobiphenyls”, 6th Intern. Balkan Workshop on Applied
Physics, July 5-7th, 2005, Constanta, Romania, Invited lecture
3.L.Frunza, A.Schönhals, S.Frunza, V.I.Parvulescu, B.Cojocaru, "Water rotational molecular
dynamics and desorption in layered oxide materials", International Symposium "Catalytic processes
on advanced micro- and mesoporous materials", September 2-5, 2005, Nessebar, Bulgaria, Poster
4.L.Frunza, C.Miclea, L.Amarande, M.C.Valeanu, B.Popescu, F.Tolea, A.Dittmar, I.Sandulescu,
C.Preda, V.I.Parvulescu, "Is combustion kinetics relevant for the reactions taking place on
perovskites and ferrites?", 3rd CONCORDE Workshop "Microkinetic Analysis as Tool for
Evaluation of Nanostructured Oxidic Catalysts" Berlin, Germany, 16-17 September 2005, Poster
5.L.Frunza, S.Frunza, A.Schönhals, "Insight into the physical basis of the water-host interaction
as obtained by broadband dielectric spectroscopy", Intern. Symposium "Catalysis on oxide-type
materials. Theory and experiment : share needs and capabilities", Krakow, Poland, November 17-19,
2005, Poster
6.L.Frunza, S.Frunza, A.Schönhals, "Water nanoclusters inside the nanocavities: dynamical
behavior" National Seminar on Nanoscience and Nanotechnology, Romanian Academy, Bucharest,
18 January 2005, Oral presentation
7.L.Frunza, C.Miclea, L.Amarande, C.I.Miclea, I.Bibicu, D.Tarabasanu, L.Diamandescu,
D.Macovei, I.Zgura, C.Negrila, "Metal oxides with cubic structure obtained by nonconventional
methods. Applications in catalysis", Seminar of Information and Discussion, Romanian Academy,
Bucharest, 17 January 2005, Poster
8.L.Frunza, C.Miclea, L.Amarande, M.C.Valeanu, B.Popescu, D.Tarabasanu-Mihaila,
L.Diamandescu, "Proiectul CONCORDE si coordonarea cercetarii in oxizi catalitici
nanostructurati", Seminar ROMNET-ERA "Nanotechnologies: opportunities for Est Europe", 12th
April 2005 , Comerce Chamber of Bucharest, Oral presentation
9.L.Frunza, I.Zgura, C.Negrila D.Tarabasanu-Mihaila, L.Diamandescu, C.Logofatu, M.Lazarescu,
D.Macovei, M.Feder, P.Kölsch, U.Bentrup, "Thermal stability and phase transitions for oxide
materials with cubic structure" National Physics Conference, Bucharest, 13-16 September 2005,
Poster, S4
57
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10.L.Frunza, T.Beica, R.Moldovan, I.Zgura, S.Frunza, "Polymeric layers for liquid crystal
alignment. Study by optical microscopy", National Physics Conference, Bucharest, 13-16 September
2005, Poster, S5
11.L.Frunza, "Experimental design applied to the synthesis of some molecular sieves",
Microsymposium NIMP, Magurele, 21th April 2005, Oral presentation
12.L.Frunza, "Determinarea structurii materialelor oxidice prin metode spectroscopice. Rolul
acestor determinari in prepararea catalizatorilor prin metode de design experimental ", Workshop
"Nano-oxides in Catalysis", Bucharest, Society of Catalysis in Romania, 24th June 2005, oral
presentation
13.T.Beica, R.Moldovan, I.Zgura, S.Frunza, " Method to study the temperature dependence of the
interfacial tension at the interface liquid crystal/ isotropic liquid ", Rom. Intern. Conf. Chem. Chem.
Engn.- RICCCE XIV, September 22–24, Bucharest, Oral presentation, S03-O-07, 2005
14.L.Frunza, C.Negrila, C.Miclea, L.Amarandei, A.Dittmar, H.Kosslick, R.Fricke, "Study of
superficial layer of some piezoelectric perovskits", Rom. Intern. Conf. Chem. Chem. Engn.RICCCE XIV, September 22–24, Bucharest, Poster S03-P-29, 2005
15.L.Frunza, S.Frunza, A.Schonhals, "Water molecular dinamics in the pores and cavities of
molecular sieves. Dielectric spectroscopy studies", Rom. Intern. Conf. Chem. Chem. Engn.RICCCE XIV, September 22–24, Bucharest, Poster S03-P-30, 2005
16.L.Frunza, C.Negrila, C.Miclea, L.Amarandei, A.Dittmar, H.Kosslick, R.Fricke, "Surface layer
of some piezoelectric perovskites", Rom. Intern. Conf. Chem. Chem. Engn.- RICCCE XIV,
September 22–24, Bucharest , Poster S08-P-14, 2005
17.L.Frunza, A.Schönhals, S.Frunza, V.I.Parvulescu, B.Cojocaru, "Dynamics of molecules and
water desorption in layered oxide catalysts", 12th Intern. Conf. Nonconventional Technol.
ICNcT2005, November 3-4, Bucharest, Poster S5, 2005
18.L.Frunza, I.Zgura, A.Schönhals, T.Beica, S.Frunza, "Studiul stratului de suprafata in
composite aerosil-cianobifenil cu continut mare de silice", A 12-a Conf. Intern. Tehnologii
Neconventionale ICNcT2005, November 3-4 2005, Bucharest, poster S10
19.S.Frunza, L.Frunza, T.Beica, I.Zgura, A.Schönhals, "Dynamics of surface layer in
cyanobiphenyl-aerosil nanocomposites with a high silica density", Exhibition of Romanian Research
„SALONUL CERCETĂRII – 2005”, 4-8 October 2005, poster
20.L.Frunza, S.Frunza, I.Nicolaie, H.Kosslick, I.Pitsch, A.Dittmar, R.Fricke, "Embedding a
manganese(III) salen complex into nanoporous molecular sieves. Host-guest interactions",
Exhibition of Romanian Research „SALONUL CERCETĂRII – 2005”, 4-8 October 2005, poster
58
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A. Serghei – PhD student in Physics, Leipzig University, Germany. Thesis on “Confinement effects
on the molecular dynamics in thin polymer films” was defended in December 2005, under the
leadership of Prof. F. Kremer.
I. I. Zgura – PhD student in Physics, Faculty of Physics, University Bucharest, Romania
C.GROUP OF NANOSTRUCTURATED MATERIALS
HEAD : Dr. MARIAN SIMA
E-mail:[email protected]
Tel: (+4021) 493 01 95
Fax:(+4021) 493 02 67
RESEARCH TEAM: 5
1. Dr. Marian SIMA
2. Dr. Victor GHIORDANESCU
3. Dr. Marin NEDELCU
4. Dr. Mihail SECU
5. Dr. Corina SECU
senior researcher III (guest)
researcher
- Synthesis, photoluminescence and thermoelectric properties of semiconductor nanofiber arrays
- New materials for “X-ray Digital Radiography” (XRD) for recording images in medical diagnostics
and non-destructive testing using PSL (“photostimulated luminescence”) effect: BaX2:RE, (X=Br,
Cl, RE=Eu2+, Ce3+).
- Detection of the irradiated foodstuff through optical methods, thermoluminescence and optically
stimulated luminescence.
1.Manganese and copper doped CdS nanostructures photoluminescence
Using a special experimental arrangement layers of pure and doped CdS nanocrystals were prepared
inside the pores of PET ion track membranes. Optical absorption data for these nanostructures
showed a variation of the bandgap value as a function of both the pore size and doping. In all
nanostructures a blue shift was observed when compared with the data for bulk materials. When
compared to pure CdS structures the doping with Mn2+ ions causes a blue shift while doping with
Cu+ induces a red shift in the absorption of the doped CdS. Photoluminescence
59
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data showed that the CdS structures present a near band-to-band excitonic luminescence and a defect
related band with longer wavelength. Doping influences strongly the position and intensity of
the luminescence bands. The excitation spectrum of Mn doped samples were used for determining
the energy levels structure for this impurity.
2.Electrochemical growth of ZnO nanorod arrays
ZnO nanorods arrays were prepared by cathodic electrodeposition from aqueous solution containing
0.1M Zn(NO3)2, at pH=6 into the pores of a polycarbonate ion track membrane. The
electrodeposition process was studied by impedance spectroscopy and cyclic voltammetry methods.
As–grown samples were characterized and analyzed by X-ray diffraction, scanning and transmission
electron microscopy and energy-dispersive X-ray spectroscopy.
3. PbSe and PbTe nanofibers and microtubes
We fabricated PbTe and PbSe nanowires and microtubes using electrochemical deposition and
template method. The morphology of nanowires and microtubes was observed by scanning electron
microscopy and the composition of these semiconductor nanostructures was measured by energy
dispersive X-ray analysis (EDX). The reflection spectra, Seebeck coefficients, thermal and electrical
conductivities have been obtained for PbTe and PbSe nanotubes arrays.
4. Photostimulated luminescence (PSL) and thermoluminescence in BaX2:RE, (X=Br, Cl,
RE=Eu2+,Ce3+) crystals
We have shown that F-type centres, unperturbed and perturbed (for Ce3+), and hole type centres are
formed during the irradiation. Optical stimulation of F centre’s electrons induces an optically
activated recombination with the holes trapped by the rare earth (RE) impurity with the formation of
an STE (“self trapped exciton”) as intermediate step. The STE recombination energy is transferred to
the RE activator followed by its characteristic luminescence. Thermoluminescence is due to a
thermally activated recombination between the F-type centres, unperturbed and perturbed (for Ce3+),
and hole type centres followed by RE characteristic luminescence. These studies are relevant and
very useful for the development of the transparent glass ceramics as a new class of materials for Xray digital radiography with higher resolution, in which optically active BaX2:RE, (X=Br, Cl,
RE=Eu2+,Ce3+) nano-crystallites (10-100 nm) have been found.
5. Detection of the irradiated foodstuff through optical methods
Using optical methods, thermoluminescence (TL) and optically stimulated luminescence (OSL), we
have put in evidence radiation treatments effects of foodstuff (spices and potatoes). TL
measurements performed on silicates (feldspars) minerals extracted using standard physico-chemical
procedures have shown a strong TL peak at about 270C in the gamma irradiated samples. A strong
OSL signal has also been observed in the blue region of the spectrum (at about 400 nm) for 830nm
stimulation.
1.V.Ghiordanescu, M.Sima, I.Enculescu, M.N.Grecu, L.Mihut, M.Secu, R.Neumann, „Manganese
and copper doped CdS nanowires photoluminescence”, Phys. Status Solidi (a), 202, 449-454, 2005
60
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2.I.Enculescu, M.Sima, V.Ghiordanescu, M.Secu,
nanowires”, Chalcogenide Letters, 2, 9-15, 2005
“Metal
chalcogenide
semiconductor
of CdS:Mn2+:Cu+ nanostructures”, J.Optoelectron.Adv.Mater, 7, 1949-1955, 2005
4.M.Sima, I.Enculescu, E.Vasile, “Preparation of metal chalcogenides semiconductor nanowires
and microtubes”, Romanian Reports in Physics (accepted)
5.J.Selling, G.Corradi, M.Secu, S.Schweizer,“Luminescence properties of the X-ray storage
phosphor BaCl2:Ce3+ comparison with BaBr2:Ce3+”, Journal of Physics: Condensed Matter 17,
8069–8078, 2005
6.S.Schweizer, L.W.Hobbs, M.Secu, J.M. Spaeth, A.Edgar, G.V.M.Williams, J.Hamlin,
"Photostimulated luminescence from fluorochlorozirconate glass-ceramics and the effect of
crystalline size", Journal of Applied Physics 97, 083522, 2005
CONFERENCES:
1.M.Sima, I.Enculescu, E.Vasile, T.Vişan, “Electrochemically synthesis of nanowires network
containing lead telluride using the membrane with controlled porosity”, Rom. Int. Conf. on Chem
and Eng.Chem., RICCCE XIV, Bucuresti 22-24 sept. 2005, Proceedings-Vol. 2, sctiunea 10, p 19-28
of CdS:Mn2+:Cu+ nanostructures”, 2-nd International on Amorphous and Nanostructured
Chalcogenides, Sinaia, Romania, June 20-24, 2005
3.J.Selling, G.Corradi, M.Secu, S.Schweizer, “Radiation defects in rare earth doped barium
dihalides X-ray storage phosphors”, SCINT 2005, accepted for publishing in Radiation
Measurements
4.B.Henke, M.Secu, U.Rogulis, S.Schweizer, J.M.Spaeth, “Optical and magneto-optical studies on
Mn-activated LiBaF3”, Proceedings of the 15th International Conference on defects in Insulating
Materials ICDIM-2004, Riga LATVIA , Physica Status Solidi (c) 2, No. 1, 380-383, 2005
5.S.Schweizer, M.Secu, J.M.Spaeth, A.Edgar, G.V.M.Williams, “Photostimulable defects in nanocrystallites in fluorozirconate glasses”, Proceedings of the 15th International Conference on Defects
in Insulating Materials ICDIM-2004, Riga LATVIA, Physica Status Solidi (c) 202, No. 2, 243-249,
2005
6.S.Polosan, E.Apostol, M.Secu, G.Aldica, “BGO glasses for scintillation detectors”, Proceedings
of the 15th International Conference on defects in Insulating Materials ICDIM-2004, Riga LATVIA,
Physica Status Solidi (c) 2, No. 1, 93-96, 2005
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7.E.Apostol, L.Toma, S.Polosan, M.Secu, V.Topa, “Z (Ag-) centres in NaCl:(Ag+ + Ca2+) crystals”,
Proceedings of the 15th International Conference on defects in Insulating Materials ICDIM-2004,
Riga LATVIA, Physica Status Solidi (c) 2, No. 1, 699-703, 2005
EDUCATIONAL ACTIVITIES: - Licence diploma with 2 students from Faculty of Physics, University of Bucharest
- V. Vasile enroled for MSc degree Faculty of Physics, University of Bucharest
D.GROUP OF ORGANIC CRYSTALS. IONIC CONDUCTIVITY AND
ELECTRODIFFUSION
HEAD: Dr. ANCA STANCULESCU
Tel: (+4021) 493 01 95
Fax:(+4021) 493 02 67
RESEARCH TEAM: 4
1. Dr. Anca STANCULESCU
2. Dr. Ionut ENCULESCU
3. Drd. Marcela SOCOL
4. Mihaela ENACHE
Our research activity was focused on: a) molecular crystal growth of organic compounds with
low thermal conductibility and high supercooling; b) investigation of the electronical and optical
phenomena in organic materials with conjugated bounds for special applications in electronics and
photonics; c) nanophases in the composite systems based on a non-crystalline organic matrix; d)
preparation of metallic and semiconductor nanowires and nanotubes with applications in optics,
electronics and magnetism.
1. Investigations on the electrical conductivity of some benzene substituted derivatives
62
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The influence of inorganic/organic doping on the I-V plots of silicon/wide-gap organic
semiconductor/silicon heterostructures has been analysed. The most significant increase in the
conductance has been obtained for organic crystalline films of benzil doped with 3 wt %m-DNB and
m-DNB films doped with 1 wt % oxine or 10 wt % resorcinol. We have remarked an increase in the
conductance of the organic films of m-DNB doped with oxine or resorcinol in heterostructures
realized with chemically polished, “n” type single crystal silicon wafers, compared to lapped ones. A
special type of conduction mechanism given by a Poole-Frenkel dependence was evidenced in
organic (resorcinol) doped meta-dinitrobenzene in the low voltages range.
2. Optical properties investigation of polycarbonate organic matrix/cadmium sulphide clusters
composite material
The effect of the heat treatment temperature (90 oC or 150 oC) on the position and shape of the
fundamental absorption edge has been studied in bisphenol. A polycarbonate organic matrix/CdS
clusters composite material was investigated for given substrate, drying conditions and duration (1.5
h or 0.5 h) of the heat treatment. A large blue shift of the absorption edge was evidenced in films
prepared in vertical configuration and thermally treated at 90 oC for 1.5 h, which can be associated
with a small dimension of the CdS crystallites and in consequence with quantum confinement
effects. Using the effective mass theory we have deduced a crystallite dimension in the range 8.8-15
nm. We also have studied the interaction of the light with this composite material evaluating an
optical band gap between 2.92 and 3.69 eV (depending on the preparation and annealing conditions)
and an absorption mechanism in CdS clusters closer to an indirect transition and deviated from the
normal direct absorption process in bulk CdS semiconductor.
3. Nickel nanotubes prepared by electroless deposition in ion track templates
Nickel nano- and microtubes were prepared by electroless deposition in ion track template
membranes. By chosing the appropriate etching conditions membranes with cylindrical or connical
pores were obtained allowing the preparation of cylindrical or connical tubules. The activation of the
membranes was a two step process. The bath used for deposition was an acidic one. Typically for
acidic bath deposition, a phosphorous content of up to 10 % was found by energy dispersive X ray
analysis in the deposit.
1.A.Stanculescu, L.Tugulea, H.V.Alexandru, S.Antohe, F.Stanculescu, M.Socol, "Molecular
organic crystalline matrix for hybrid organic-inorganic (nano) composite materials", J. Cryst.
Growth, vol. 275/1-2, p. e1779-e1786, 2005
2.A.Stanculescu, F.Stanculescu, H.V.Alexandru, M.Socol, "Doped aromatic derivatives wide-gap
crystalline semiconductor structured layers for electronic applications”, Thin Solid Films, vol. 495,
nr. 1-2, p. 389-393, 2005
63
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3.M.Daub, I.Enculescu, R.Neumann, R.Spohr, “Ni nanowires electrodeposited in single ion track
templates”, J.Optoelectron.Adv.Mater. 7, 865-870, 2005
of Cds : Mn2+: Cu+ nanostructures”, J.Optoelectron.Adv.Mater. 7 (4), 949-1955, 2005
CONFERENCES:
1.A.Stanculescu, F.Stanculescu, L.Tugulea, M.Socol, "Optical properties of 3,4,9,10perylenetetracarboxylic dianhydride and 8-hydroxyquinoline aluminium salt films prepared by
vacuum deposition", Section:”Polymers, molecular materials and biomaterials”, Materials 2005,
20-23 March, Aveiro, Portugal
2.A.Stanculescu, F.Stanculescu, “Some investigations on the optical properties of microcomposite
semiconductor doped glasses”, Section: “Nano and microstructured materials”, Materials 2005, 2023 March, Aveiro, Portugal
3.A.Stanculescu, F.Stanculescu, H.V.Alexandru, M.Socol, "Doped aromatic derivatives wide-gap
crystalline semiconductor structured layers for electronic applications”, Section: “Synthesis,
characterization and applications of mesostructured thin layers”, E-MRS 2005, May 31-June 3,
Strasbourg, France
4.A.Stanculescu, F.Stanculescu, M.Socol, "Nonstoichiometric vapour phase transport process in
the system ZnSe :I2 ", Section : "Coatings & Surface Engineering", EUROMAT 2005, 5-8
September, Prague, Czech Republic
5.M.Socol, A.Stanculescu, "Investigations of the nonhomogeneities in organic molecular
crystalline materials using Kubelka-Munk theory", 6th International Balkan Workshop on Applied
Physics July 5-7th, 2005, Constanta, Romania
6.A.Stanculescu, “Doped organic crystals”, 6th International Balkan Workshop on Applied
Physics July 5-7th, 2005, Constanta, Romania
7.A.Stanculescu, F.Stanculescu, M.Socol, "Optical properties of polycarbonate organic matrix/
cadmium sulphide clusters composite", International Conference on Fundamental and Applied
Research in Physics, 26-29 October, Iasi, Romania
8.F.Stanculescu, A.Stanculescu, M.Socol, "Light absorption in meta-dinitrobenzene and benzyl
crystalline films”, International Conference on Fundamental and Applied Research in Physics, 2005,
26-29 October, Iasi, Romania
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E.GROUP OF POINT DEFECTS SPECTROSCOPY IN OPTICAL MATERIALS
HEAD: Dr. SILVIU POLOSAN
Tel (4021) 493 01 95
Fax (4021) 493 02 67
RESEARCH TEAM: 3
1. Dr. Silviu POLOSAN
2. Dr. Elena APOSTOL
3. Dr. Monica ENCULESCU
Prof. Dr. Vladimir TOPA*
M.C. of Romanian Academy
*
senior researcher I (guest)
Institute of Mathematics "Simion Stoilow" of Romanian Academy, Bucharest
1.Study of the optical properties of alkali halide crystals doped with ions of heavy metals
2.Obtaining and study of nano-sized metallic structures
3.Study of irradiation induced effects (gamma and swift heavy ions) in pure and doped alkali halide
crystals
1.The study of the optical properties of ionic aggregates of heavy metals in doped alkali halides
lead to following results:
-the formation of new alkali halide crystals doped with silver and co-doped with bivalent ions and
alkali metal ions (Na, Li, Rb si Cs). The replacement of the alkali ion leads to changes of the
absorption bands which proved the presence of alkali ions in the composition of the new centers;
-it was proved that directly from electrolytical colouring one can obtain the centers Ag-(Na+) and Ag(Li+) and it was identified the center Ag-(Rb+);
-in crystals doped with silver and copper the electrolytical colouring in non-conventional conditions
(low temperatures and high electric field) leads to the appearance of new centers which do not
appear in conventionally colored crystals,
- development of a method to calculate the shape of absorption bands for cationic ions (ex Tl+)
which was used in the case of anionic ions Ag- in KCl crystals.
2.Obtaining and study of nano-sized metallic structures
-for both electrolytical colouring or by thermal treatment at temperatures between 400 and 700C
silver clusters are formed in a coral type arrangement;
- the results concerning silver nanoclusters and gold nanoclusters were obtained by two different
methods: electron microscopy and optical absorption; the numerical calculation performed on the
65
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basis of Mie theory regarding the dimension of the nanoclusters are in good agreement with the
results obtained by electron microscopy ;
-a new method for obtaining silver nanoclusters ( illumination combined with a thermal treatment at
temperatures below 250C) in KCl, KBr and KI having low diameters ;
-the nanoclusters exhibiting a spatial arrangement of coral type have a scale invariant character. The
formation mechanism is based on cluster-cluster diffusion limited aggregation (DLA) and can
explain short times necessary to obtain this effect;
3.The study of irradiation induced effects (gamma and swift heavy ions) in alkali halide crystals
pure and doped is the newest research direction which we approached:
-we performed spectroscopy and microscopy studies (optical and electron microscopy) regarding the
defects created as a consequence of swift heavy ions irradiation (at different fluences) and as a
consequence of gamma irradiation.
-for the first time studies regarding the swift heavy ions irradiation for doped alkali halides were
performed.
-Bilateral Cooperation Agreement NIMP-Bucharest Romania - Gesellschaft fur
Schwerionenforschung mbH (GSI), Darmstadt, Germany
”Defects Produced in Alkali Halide Crystals by Heavy Ion Irradiation”, 2003-2005
Resp. NIMP (INCDFM): Dr. Monica Enculescu.
- International cooperation with Kyoto University (Prof. Dr. Taiju Tsuboi), Japan.
”Obtaining of Advanced Materials: Complex Spectroscopic Studies of Negative Heavy Metal Ions
in Ionic Crystals”
Resp. NIMP (INCDFM): Dr. Silviu Polosan.
PUBLISHED PAPERS:
1.M.Enculescu, K.Schwartz, C.Trautmann, „Heavy ion induced damage in NaCl and KCl
crystals”, Nuclear Instruments and Methods B, 229, (3-4), 397, 2005
2.M.Enculescu, “Swift heavy ion irradiation effects on doped alkali halides”, Journal of
Optoelectronics and Advanced Materials, 7, No. 6, 3047, 2005
3.V.Topa, T.Tsuboi, S.Polosan, E.Apostol, “New perturbed Pb- -aggregate centres in
electrolytically colored KBr :Pb2+ + (Ca,Ba) crystals”, Journal of Luminescence (in press)
4.S.Polosan, T.Tsuboi, V.Topa, “The role of Eu2+ on the electrolytic colored KCl:( Pb+Eu)
crystals”, Journal of Physics: Condensed Matter (in press)
CONFERENCES:
1.V.Topa,T.Tsuboi, S.Polosan, E.Apostol, “New perturbed Pb- -aggregate centres in
electrolytically colored KBr :Pb2+ + (Ca,Ba) crystals”, International Conference of Luminescence,
Beijing, China July 21-26, 2005
66
Laboratory of Oxidic Materials
_____________________________________________________________________________
HEAD: Dr. CORNEL MICLEA
Tel: (+4021) 493 01 95
Fax: (+4021) 493 02 67
TOTAL EMPLOYEES: 15
RESEARCH TEAM: 11
1. Dr. Cornel MICLEA
2. Dr. Constantin TANASOIU
3. Dr. Luminita AMARANDE
4. Dr. Igor NAZARENCO
5. Dr. Alin IUGA
6. Corneliu Florin MICLEA*
7. Lucian TRUPINA
8. Elena Daniela ION**
9. Marius CIOANGHER
10. Nicolae Felix SIMA
11. Vasilica TOMA
senior researcher I
senior researcher I
researcher
* Present address: Max Planck Institute for Solid State Physics, Dresden, Germany, on leave for
PhD.
** Present address: Jozef Stefan Institute, Ljubljana, Slovenija, on leave for PhD.
1. Experimenting the metallic systems with heavy fermions at very low temperatures (0.3-20K)
under high pressures and high magnetic fields (9T)
The classical phase transition take place at finite temperatures due to the thermal fluctuations of
the order parameter. At very low temperatures (approaching absolute zero) quantum effects play
an important role and the phase transition can take place at a critical quantum point (CQP) due to
quantic fluctuation only. In the neighborhood of a CQP the effective mass of electron becomes
divergent so that the liquid Fermi theory is not valid any further and the mechanism by which the
system changes the fundamental state cannot be described by the classic theory and only
systematic experiments at very low temperature will evidence the mechanism by which the
quantum fluctuation spreads over large regions inside the material. The resistivity and specific
heat measurements at very low temperatures are able to throw some light on these mechanisms.
Consequently, we concentrated our efforts towards constructing two special “measuring pressure
cells” able to determine the resistivity and specific heat behavior at temperatures approaching
absolute zero. We had to design such cells in order to match with the Physical Properties
Measurements System (PPMS) equipment from Quantum Design.
The solution chosen for the cells was of the cylinder with piston type, having double walls. The
outer wall was made of CuBe alloy and the inner wall from a special alloy of Co, Ni, Cr, Mo,
known commercially as MP35N alloy. This alloy was subjected to a double annealing process in
order to increase its mechanical strength, since the high pressure is exerted on it. Using these
cells we measured the specific heat and the resisitivity as a function of temperature in CeCoIn5
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alloy, a typical system with heavy fermions. It was evident from these measurements that this
alloy becomes superconductor at 2.27 K.
2. Theoretical and experimental model of a hard-soft composite material.
We focused our studies to the development of such composite materials made of high anisotropy
hexaferrite phase and high magnetization spinel ferrite phase. Consequently, a complete
investigation of such hard and soft ferrites was undertaken with special references on structure
and properties of both types of ferrites. The hard hexaferrites were of the type MeO⋅6Fe2O3
where Me=Ba, Sr, and the soft ones were of the type MeO⋅Fe2O3 were Me stands for one of the
transitional elements Cu, Zn, Ni, Mn and Ti. On this basis an experimental model for such a
composite material was designed and it consisted essentially in a soft nanoparticle of certain
geometry (sphere, prism) encapsulated in a hard magnetic matrix of bigger dimensions. The
demagnetization curves as a function of the soft particle dimensions and of the matrix were
deduced taking into account the possible interactions between them and the alignment of the
magnetic moment. At the same time using Monte Carlo simulation of magnetic ordering,
different theoretical models were elaborated for different textures of the two phases.
3. An experimental prototype of thermal sensor used at high voltages
Barium titanate can be turn to a semiconductor with resistivity down to 101-102 Ω ⋅cm, by simply
doping it with a donor dopant such as Y or La in small quantities. In this state it shows an
anomaly of the R(T) curve around 120 oC where the resistivity increases dramatically with twothree orders of magnitude. This anomaly known as PTCR effect makes this material extremely
useful for application as thermal sensor. When Ba is partially replaced by isovalent ions such as
Sr and Pb, the temperature at which the PTCR effect appears is switched up (for Pb) or down (for
Sr), thus having the possibility to make thermal sensor for protection at any desired temperature
between 70o and 190 oC.
Our studies on doped barium titanate were now concentrated to produce a thermal sensor based
on barium titanate able to be used in applications where high voltages are regularly used. We
investigated a number of dopants and finally we found the optimum composition using Ca, Pb,
Sr and Y as dopants. The shape for the prototype was disk and the final encapsulation was
realized in two modes using either a special epoxy resin in which the sensor was embedded or a
kinar type retractile tube which covered the thermal sensor on which the terminals were soldered.
In both cases the basic properties remained unchanged.
4. Investigation of an experimental model of ferrimagnetic nanostructured material
The ferrimagnetic materials with high anisotropy can be found in the class of materials with the
general chemical formula MFe12O19 where M can be, in general, Ba, Sr or Pb, or a combination of
them. They are complex oxides with hexagonal compact structure and uniaxial anisotropy. In
particulate media of this type the magnetization processes depend on the morphology of the
particle ensemble. For bigger particles they take place via domain wall displacement but for
smaller ones the situation is more complicated. There is a critical dimension for single domain
particle and it depends mainly on the anisotropy. If the particle size goes down to nanometric
region, the magnetic behavior of such ensemble becomes superparamagnetic and the
magnetization processes, or reversal, take place mainly by coherent rotation.
We used an advanced technique, namely mechanochemical synthesis, to prepare a nanometric
powder of strontium ferrite in order to study the behavior of such nanomaterials. The optimum
milling time was established as being 100 h.
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5. New sensors and transducers made from PT type piezoceramic materials
Lead titanate (PT) is a piezoceramic material which cannot be used without additives because of
the high crystalline anisotropy. Stabilizing additives such as Y and Bi were used to lower the
electromechanical anisotropy and to produce high quality ceramic bodies. Such a material was
used for making piezosensor for different types of transducers. Comparatively, PZT type
ceramics were also used for sensors.
Two types of medical transducers were realized from these materials namely: a fetal pulse
transducer and a transducer for aerosol production.
6. New optoelectronic switches based on nonstoichiometric Cr2O3
The main objective of this project was the study of semiconducting chalcogenides based on
nonstoichiometric Cr2O3, in order to develop new optoelectronic switches. The results obtained
so far include: optimization of the raw chalcogenide used for photo-resistances sensitive in green
and orange spectra and the production of such photo resistances by sintero-sublimation
technique. The researches in this field are running further to obtain high quality photoresistances
at mass scale production.
PROMOTED INTERNATIONAL AND NATIONAL COOPERATION & PROJECTS
1. POLECER “European Thematic Network on Polar Electroceramics” 2001-2006, Dr. Cornel
Miclea
2. COST 525, "Advanced electroceramics: grain boundary engineering" , 2004-2005, Dr. Cornel
Miclea
3. CONCORDE, 2004-2005, Dr. Cornel Miclea
4. SCIENTIFIC COOPERATION AGREEMENT - The High Pressure Department of the Max
Planck Institute for Chemical Physics of Solids, Dresden, Germany; “Hydrostatic pressure cells
for measurements at high pressure and low temperature” - 2004-2005
EDUCATIONAL ACTIVITIES
A. PhD THESIS:
PhD Thesis in preparations - 7
Under the Leadership of Prof. Dr. Cornel Miclea
Iuliana Radu
Ion Elena Daniela
Voicu Ionel
David Cristina
Sima Nicolae Felix
Under the Leadership of Prof. Dr. Constantin Tanasoiu
Lucian Trupina
Liliana Popescu
B. MASTER:
1. Nicolae Felix SIMA-Master in Physics Courses at the Physics Faculty, Bucharest University,
October 2003- February 2005
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PUBLICATIONS
1.C.Miclea, C.Tanasoiu, C.F.Miclea, A.Gheorghiu, V.Tanasoiu, F.N.Sima, “Effect of iron and
nickel substitution on the piezoelectric properties of PZT type ceramics”, Proceedings of
Electroceramics IX, Cherbourg, France 31 May-04 June 2004, J.Europ.Cer.Soc, 25(12) 23972400, 2005
2.C.Miclea, C.Tanasoiu, C.F.Miclea, “Effect of lead titanate-zirconate additions into barium
titanate ceramics on the dielectric and piezoelectric properties of mixed compounds”,
Ferroelectrics, 319, 57-63, 2005
3.C.Miclea, C.Tanasoiu, C.F.Miclea, A.Gheorghiu, V.Tanasoiu, “Soft ferrite materials for
magnetic temperature transducers and applications”, JMMM, 290-291 1506-1509, 2005
4.C.Miclea, C.Tanasoiu, I.Spanulescu, C.F.Miclea, F.N.Sima, M.Cioangher, “Effect of
neutron irradiation on some piezoelectric properties of PZT type ceramics”, Journal de Physique
IV, 128, 115-120, 2005
5.C.Miclea, C.Tanasoiu, A.Gheorghiu, C.F.Miclea, F.N.Sima, M.Cioangher, “Influence of
forming pressure of compacted powders on densification of sintered body”, A.A. Balkema Pub.Taylor & Francis, Powders & Grains Vol. 1, 655-658, 2005
6.C.Miclea, L.Amarande, C.Tanasoiu, I.Spanulescu, C.F.Miclea, “Piezoelectric properties of
bismuth modified lead titanate ceramics”, IEEE Electron Device, 2, 271-274, 2005
7.A.Iuga, C.Miclea, C.Tanasoiu, L.Amarande, M.Cioangher, “PZT-ELASTOMER type
composite materials with 03 connectivity obtained by nonconventional technology”,
Nonconventional Technologies Review, 2,(9-10), 73-78, 2005
8.C.F.Miclea, M.Nicklas, J.L.Sarrao, F.Steglich, “Possible Fulde-Ferrell-Larkin-Ovchinnikov
superconducting state in CeCoIn5: New evidence from pressure studies”, Physica B, (in press
2005)
9.C.Miclea, C.Tanasoiu, I.Spanulescu, C.F.Miclea, “Effect of grain size and sintering
atmosphere on electrical and dielectric properties of uranium doped barium titanate ceramics”,
J. Europ. Cer. Soc. (in press 2005)
10.C.Miclea, C.Tanasoiu, C.F.Miclea, A.Gheorghiu, “Structural, electrical and dielectric
properties of uranium doped barium titanate”, Materials Science Forum, (in press 2005)
11.C.F.Miclea, H.D.Hochheimer, B.Martin, P.K.Dorhout, G.Sparn, “Non Fermi Liquid
behaviour and FFLO transition in CeCoIn5”, J. Phys. Condens. Matter (in press 2005)
12.C.F.Miclea, M.Nicklas, D.Parker, K.Maki, J.L.Sarrao, J.D.Thompson, G.Sparn, F.Steglich,
The pressure dependence of the Fulde-Ferrell-Larkin-Ovchinnikov state in CeCoIn5”, Phys. Rev.
Lett. (in press 2005)
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CONFERENCES
1.C.Miclea, C.Tanasoiu, I.Spanulescu, C.F.Miclea, F.N.Sima, M.Cioangher, “Effect of
neutron irradiation on some piezoelectric properties of PZT type ceramics”, International
Conference, Electroactive Materials and Sustainable Growth „EMSG 2005”, Paris, France, 21
-27.05/2005
2.C.Miclea, C.Tanasoiu, I.Spanulescu, C.F.Miclea, “Effect of grain size and sintering
atmosphere on electrical and dielectric properties of uranium doped barium titanate ceramics”,
IX International Conference and Exhibition of the European Ceramic Society, Portoroz,
Slovenia, 19–23.06/2005
3.C.Miclea, C.Tanasoiu, C.F.Miclea, A.Gheorghiu, “Structural, electrical and dielectric
properties of uranium doped barium titanate”, III International Materials Symposium
„MATERIALS 2005” Aveiro, Portugal, 19-24.03/2005
4.C.Miclea, C.Tanasoiu, A.Gheorghiu, C.F.Miclea, F.N.Sima, M.Cioangher, “Influence of
forming pressure of compacted powders on densification of sintered body”, International
Conference “Powders and Grains”, Stuttgart, Germany 18-23.07 2005
5.C.Miclea, L.Amarande, C.Tanasoiu, I.Spanulescu, C.F.Miclea, Piezoelectric properties of
bismuth modified lead titanate ceramics”, CAS 2005, Sinaia, Romania, 2-5 October 2005
6.A.Iuga, C.Miclea, C.Tanasoiu, L.Amarande, M.Cioangher, “PZT-ELASTOMER type
composite materials with 03 connectivity obtained by nonconventional technology”, The 12th
International Conference on Nonconventional Technologies - ICNcT2005, November 3-4 2005,
Bucharest, Romania
7.C.Miclea, C.Tanasoiu, A.Gheorghiu, C.F.Miclea, L.Amarande, M.Cioangher “Materiale
semiconductoare oxidice nanostructurate pe baza de titanat de bariu dopat pentru senzori
termosensibili”, Al 6-lea Simpozion National MATNANTECH, Jupiter, Romania, 07-11 iunie
2005
8.C.Miclea, C.Tanasoiu, A.Gheorghiu, C.F.Miclea, L.Amarande, M.Cioangher “Materiale
piezoceramice nanostructurate”, Al 6-lea Simpozion National MATNANTECH, Jupiter,
Romania, 07-11 iunie 2005
9.C.Miclea, L.Amarande, C.Tanasoiu, C.F.Miclea, “Materiale semiconductoare oxidice
nanostructurate pentru pozistoare”, Al 7-lea Simpozion National MATNANTECH, Predeal,
Romania, 02-06 noiembrie 2005
10.C.Miclea, L.Amarande, C.Tanasoiu, C.F.Miclea, “Comportarea superparamagnetica a
materialelor ferimagnetice nanostructurate pentru aplicatii speciale”, Al 7-lea Simpozion
National MATNANTECH, Predeal, Romania, 02-06 noiembrie 2005
71
NATIONAL INSTITUTE OF MATERIALS PHYSICS*ANNUAL REPORT 2005
Laboratory of Structure and Dynamics of Condensed Matter
____________________________________________________________________________________________
HEAD: Dr. LUCIAN DIAMANDESCU
Tel.: (+4021) 493 01 95
Fax: (+4021) 493 02 67
TOTAL EMPLOYEES: 19
RESEARCH TEAM: 16
The laboratory contains two distinct groups:
A. GROUP OF PHYSICS OF TRANSITIVE PHENOMENA & MÖSSBAUER
SPECTROSCOPY
HEAD: Dr. LUCIAN DIAMANDESCU
Tel.: (+4021) 493 01 95
Fax: (+4021) 493 02 67
RESEARCH TEAM: 8
Dr. Lucian DIAMANDESCU
Dr. Eng. Ion BIBICU
Dr. Mircea ROGALSKI*
Dr. Serban CONSTANTINESCU
Dr. Doina TARABASANU-MIHAILA
Dr. Marcel FEDER
Drd. Alina BANUTA
Drd. Dragos CONSTANTIN**
*
senior researcher I
senior researcher I
senior researcher I
Actual address: Instituto Superior Tecnico, Lisabona, PORTUGAL
Actual address: University of California USA, e-mail: [email protected]
**
Synthesis and characterization of new physical structures.
Mixed oxides: solvothermal versus mechano-chemical synthesis and mechanisms.
Advanced materials for sensing and photocatalitic applications.
New ceramic magnetic materials for high frequency applications.
Investigation and modeling-computation of local electric and magnetic crystal fields in staticdisorder crystalline media (synthetic or natural samples).
Mineral crystal-chemistry, ceramics and sediment dating.
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1.Oxides: unconventional synthesis, structural studies and applications
- Laser ablation deposition has been used to synthesize nanoscale ferrite structures. Our
investigations were performed on NiZn and Zn ferrite films deposited on silicons (100)
substrates. Complementary x-ray diffraction and superconducting quantum interference device
magnetometry measurements helped identify the optimum laser ablation deposition conditions
for obtaining the desired nanoferrite structures. The zero field cooled–field cooled (ZFC–FC)
magnetization, M (T), curves yielded the value of the blocking temperature in both NiZn and Zn
ferrite systems
- Mixed oxide nanoparticles system xTiO2-(1-x)α-Fe2O3 (x = 0.0-1.0) has been obtained using
both hydrothermal and ball milling routes. X-ray diffraction (XRD), Mössbauer spectroscopy and
transmission electron microscopy reveal the formation of nanoscaled solid solutions. Rietveld
refinements of the XRD spectra have been performed to study the preferential sites of Ti4+ ions in
hematite corundum lattice as well as of Fe3+ ions in TiO2 structure. By increasing titanium
concentration, the α-Fe2O3 phase containing Ti4+ ions decreases simultaneously with the increase
of TiO2 structure containing substitutional iron ions. The mean particle dimension decreases
generally to 10 nm as the molar fraction x increases up to x=1.0. The solubility limits and the
influence of the synthesis parameters on the structure and morphology of final products are
discussed
- Thin films (50 nm) of Fe100-xPdx and Fe100-xMnx (x=20 and 50) were deposited by laser ablation
on a Si wafer and studied by X-ray diffraction (XRD) and conversion electron Mössbauer
spectroscopy (CEMS). For the Fe80Pd20 thin film, XRD spectra show the formation of FePdx,
iron, Pd oxide and traces of hematite in the ablated film. Complementary information obtained
by CEMS indicates the presence of an upper 50-nm thick surface layer of hematite in the
deposited film. Fe50Pd50 phase was observed by CEMS and a Pd oxide component was identified
by XRD, along with traces of hematite. In the case of Fe80Mn20, the CEMS spectrum is
consistent with the occurrence of the antiferromagnetic FeMn phase and the XRD pattern also
shows the presence of Fe in the structure. For the system Fe50Mn50, we obtain by CEMS an
antiferromagnetic phase of FeMn and by XRD we trace the presence of nanohematite and indepth iron.
2.Mössbauer spectroscopy applications
- Samples of RFe3 (R=Dy, Sm, Y) were doped with Si, Al and Ti and studied by Mössbauer
spectroscopy and X-ray diffraction. Most Mössbauer spectra were analyzed with three sextets,
corresponding to the 6c, 3b and 18h inequivalent lattice sites for iron. A quadrupole split doublet
was also present in some spectra, which became dominant for the case of Al substitution. The
collapse of the hyperfine magnetic structure is a magnetic effect due to substitutions: the X-ray
diffraction patterns yielded a particle size of about 100 nm, thus precluding the occurrence of
superparamagnetism in these systems
- The inhibiting effect of N-ciclohexil-benzothiazole-sulphenamida (NCBSA) on the corrosion of
carbon- steel in diluted ammonia solution at room temperature has been studied by Mössbauer
spectroscopy, electrochemical measurements, weight loss measurements and surface microscopic
analysis
- The data-correlation obtained by x-ray photoelectron spectroscopy (XPS), Mössbauer
spectroscopy and electrical resistivity measurements techniques on the magneto resistive (MR)
compounds Sr2FeMoO6 evidenced the mixed valence states involving around of Fe (3s) and Mo
(3d) states at the grain boundaries. Mössbauer studies confirm the presence of a valence
73
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fluctuation state and indicate the presence of an electron jumps from a Fe2+ ion to a Mo6+ ion
leading to a Fe3+-Mo5+ configuration, and vice versa.
Protocol for scientific cooperation with the Physics Department Duquesne University, Pittsburgh,
USA
Project title: Solvothermal elaboration and the study of physical properties of some substitute
oxide structures (2002-2007).
Physics Department, Instituto Superior Tecnico, Lisbon, Portugal
Project title: Measurements and characterization of some iron oxide compounds by Mössbauer
spectroscopy.
Protocol for scientific cooperation with "Geomaterials and Engine Geology, Institute Francilien
of Geosciences, University of Marne la Vallée, France
Project title: Natural semiconductors (arsenopyrite and tourmaline) and gold ores/
mineralization, the crystallo-chemistry investigation of arsenopyrite minerals (structural
association, defects and traps of gold) from South Carpathians deposits (Valea Stan, Costesti
Jidostita). (2006-2009)
1.M.Sorescu, L.Diamandescu, A.Grabias, “Laser ablated Fe100-xPdx and Fe100-xMnx thin films
(x=20 and 50)” accepted Intermetallics
2.M.Sorescu, L.Diamandescu, M.Valeanu, “Substitutional effects in RFe3 intermetallics (R=Dy,
Sm, Y)”, Intermetallics 14, 332-335 (2006)
3.M.Sorescu, L.Diamandescu, D.Tarabasanu-Mihaila, “Recoilless fraction of tin-doped
hematite nanoparticles obtained by hydrothermal synthesis”, Materials Letters 59, 22-25, 2005
4.M.Sorescu, C.Y.Um, M.E. Mc Henry, L. Diamandescu, “Thermal behaviour of substituted
FeCo-based metallic glasses”, Journal of Non Crystalline Solids 351, 8-9, 663-667, 2005
5.M.Sorescu, L.Diamandescu, R.Swaminathan, M.E. McHenry, M.Feder, “Structural and
magnetic properties of NiZn and Zn ferrite thin films obtained by laser ablation deposition”,
Journal of Applied Physics 97 (10): G105, 1-3, Part 2, 2005
6.R.Swaminathan, M.E.McHenry, S.Calvin, M.Sorescu, L.Diamandescu, “Surface structure
model of cuboctahedrally truncated ferrite nanoparticles”, Journal of American Ceramic
Society, in press
7.A.Samide, I.Bibicu, M.S.Rogalski, M.Preda,“Surface study of the corrosion inhibition of
carbon steel in diluted ammonia media using N- ciclohexil-benzothiazole-sulphenamida”,
Corrosion Science 47, no. 5 1119-1127, 2005
8.S.E.Enescu, I.Bibicu, “Rayleigh scattering of Mössbauer radiation method used in dynamics
studies of condensed matter”, Acta Physica Polonica A 107, 479-489, 2005
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9.A.Samide, I.Bibicu, B.Tutunaru, M.Preda, “Studiul suprafetei oţelului-carbon corodat in ape
industriale care contin NH3/NH4Cl utilizând spectrometria Mössbauer“, Revista de Chimie
Bucuresti 56, 8, 2005 (in romanian, accepted)
10.I.Bibicu, A.Samide, M.Preda, “Mössbauer spectroscopy studies on steel corrosion in diluted
ammonia media”, U. P. B. Sci. Bull. Ser. A, 2005 (accepted for publication)
11.S.Constantinescu, L.Gheorghe, C.Stoicescu, S.Georgescu, O.Toma , I.Bibicu, “Growth and
XRD, optical and Mössbauer investigations of Eu doped trigonal La- Gallosilicate crystal”,
Rom. Rep. Phys 57, nos. 2, 249-260, 2005
12.S.Constantinescu, “Mössbauer investigation of static-disorder crystalline media. III
Dispersion of electric and magnetic hyperfine fields”, Rom. Rep.Phys. 57, nos. 1, 85-98, 2005
13.S.Constantinescu, “Mössbauer investigation of static-disorder crystalline media. VI
Modelling procedure of hyperfine fields dispersion in static-disorder crystalline media”, Rom.
Rep. Phys. 57, nos. 1, 99-125, 2005
14.M.Raekers, K.Kuepper, H.Hesse, I.Balasz, I.G.Deac, S.Constantinescu, E.Burzo,
M.Valeanu, M. Neumann, “Investigation of chemical and grain boundary effects in highly
ordered Sr2FeMoO6 : XPS, Mössbauer studies”, accepted J.O.A.M, 2005
BOOKS:
M. S. Rogalski and S. B. Palmer-ADVANCED UNIVERSITY PHYSICS
Second edition, 1024 pagini
Chapman and Hall/CRC, 2005
ISBN: 1584885114
S. Constantinescu - ELEMENTE INTRODUCTIVE IN FIZICA SOLIDULUI
Note de curs, 388 pagini
"Valahia University Press", S.C. Bibliotheca S.R.L. Targoviste
ISBN: 973-8135-86-9
CONFERENCES:
1.R.Swaminathan, M.E.McHenry, S.Calvin, M.Sorescu, L.Diamandescu, ”Surface structure
model of cuboctahedrally truncated ferrite nanoparticles”, Ninth International Conference On
Ferrites (ICF9): Proceedings of the International Conference On Ferrites (ICF9) San Francisco,
California (2004) Editor R. F. Soohoo, Amer.Ceramic Society, March 2005, p. 847-852
2.O.F.Caltun, M.Feder, V.Vilceanu “Microstructure, electrical and magnetic properties of high
permeability MnZn ferrite with Bi2O3 additions”, Ninth International Conference On Ferrites
(ICF9): Proceedings of the International Conference On Ferrites (ICF9) San Francisco, California
(2004)Editor R.F.Soohoo, Amer.Ceramic Society, March 2005, p. 251-256
3.A.Samide, I.Bibicu, B.Tutunaru, M.Preda, “The study of the mechanism of the corrosion
inhibition of carbon steel in a solution of ammonium chloride using N-cyclohexyl-benzothiazolesulphen-amide” (NCBSA). Conferinta Nationala de Chimie, Bucuresti 2005
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4.S.E.Enescu, I.Bibicu, “Dynamics studies in condensed matter by Rayleigh scattering of
Mössbauer radiation” 14th National Conference on Physics, Bucharest, 13-17 September 2005,
ABSTRACTS vol.1 p. 50-51
5.I.Bibicu, A.Samide, M.Preda, “Mössbauer spectroscopy studies on steel corrosion in diluted
ammonia media” 14th National Conference on Physics, (1st Symposium on Technical Physics and
Physical Engineering) Bucharest, 13-17 September 2005, ABSTRACTS vol.2 p. 20-21; (Oral
presentation)
6.I.Bibicu, “Mössbauer spectroscopy: a method for in situ characterization of catalysts”
(invited lecture) “2nd CONCORDE Workshop Belfast – Northern Ireland, 18th -19th February
2005” (NMP2-CT-2004-505834; CT 33 – SW2)
7.I.Bibicu, “Comparative transmission and backscattering measurements on Eu-151”,
International Conference on the Applications of the Mössbauer Effect (ICAME 05) September
5-9, 2005, Montpellier, France, Abstracts Volume, T6-P2
8.S.Constantinescu, M.N.Grecu, I.Bibicu, S.Georgescu, “NGR, EPR and optical spectroscopy
investigations in RE-dopped trigonal gallogermanate crystals”, 6th International Workshop on
Applied Physics, Constanta, Romania, July 5-7, 2005, Abstracts, p. 60 (S1 P15) POSTER
9.L.Frunza, I.Zgura, C.Negrila, D.Tarabasanu-Mihaila, L.Diamandescu, C.Logofatu,
M.Lazarescu, D.Macovei, M.Feder, P.Kőlsch, U.Bentrup, “Thermal stability and phase
transitions for oxide materials with cubic structure”, Conferinta Nationala de Fizica, 12-16 09
2005
10.S.Constantinescu, “Dispersion of electric and magnetic hyperfine fields in extremely content
of Fe in gallo-germanates”, International Conference on the Applications of the Mössbauer
Effect, ICAME 2005, Sept. 5-9, 2005, Montpellier, France, Abstract Book, T8-P19, POSTER
11.S.Constantinescu, S.T.Redfern, “Recent 57Fe Mössbauer investigations of fayalite-tephroite
series extracted from Fe-Mn deposit at Razoare”, International Conference on the Applications
of the Mössbauer Effect, ICAME 2005, Sept. 5-9, 2005, Montpellier, France, Abstract Book, T4P20, POSTER
12.S.Constantinescu, “Static-disordered crystalline-media investigated by Mössbauer
spectroscopy”, 6th International Workshop on Applied Physics, Constanta, Romania, July 5-7,
Abstract Book, S3, P23, 2005
13.S.S.Udubasa, S.Constantinescu, Gh.Udubasa, “ Mineralogy of the shear-zone related gold
ores I. Gold composition vs. host minerals”, Annual Scientific of Geological Society of
Romania, 21-25 May, 2005, Rosia Montana, 136-140
PhD THESIS:
A. Banuta: Ph Degree in physics, September 2005
76
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B: GROUP OF ELECTRON MICROSCOPY, X-RAY AND NEUTRON DIFFRACTION
HEAD: Dr. FLORIN VASILIU
Tel.: (+4021) 493 01 95
Fax: (+4021) 493 02 67
RESEARCH TEAM: 8
Dr. Florin VASILIU
Dr. Nicolae POPA1
Dr. Nicoleta POPESCU-POGRION
Dr. Corneliu SARBU
Liviu DUMITRACHE
Gabriela ALEXE2
Manuela STIR3
Ionel MERCIONIU
senior researcher I
senior researcher I
senior researcher I
senior researcher I
1
Actual address: Joint Institute for Nuclear Research, Lab. Neutron Physics, Dubna, RUSSIA
Actual address: Ph. D fellowship at Bremen University, GERMANY
3
Actual address: Ph.D fellowship at Rostock University, GERMANY
2
PRESENT RESEARCH INTEREST
Structural characterization of ferroelectric layers, advanced ceramics, oxide semiconductors
Investigation of material microstructure by X-ray and neutron powder diffraction.
1. New insight into the dislocations structure to explain the SrTiO3 plasticity at low temperatures
The dislocations structure induced by the plastic deformation of SrTiO3 single crystals at 115K
has been further investigated by WB-DF technique in the TEM, in collaboration with the Max
Planck Institute for Metals Physics in Stuttgart, Germany. No dislocation dissociation could be
observed, which is unusual in this kind of materials. A contribution to the understanding of the
processes involved in the dislocations movement during plastic deformation has got support by
this result and a model for that movement has been submitted for publication in 2006, in the
jubiliar issue of the Philosophical Magazine A dedicated to the 50-th anniversary of the first
observation of a dislocation by transmission electron microscopy.
2. Computational models for simulating the developed low Y doped α-alumina; uniform huge
grains system
In order to obtain the performed ceramics with high resistance to the electric breakdown and
good thermo-mechanical properties (creep resistance, elasticity, thermal shock resistance) were
studied the structure of the grains and the microstructure and the microchemistry of the grain
boundaries (GB). In addition, development of physical models was attempted, which related the
morphology with mechanical and transport properties in the case of huge uniform grains system.
77
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Furthermore, statistical analysis on fracture experiments based on bending strength
measurements was conducted to obtain characteristics strength parameters (e.g. mean strength,
Weibull modulus). Investigations in order to relate structural properties, processing methods and
the characteristic strength parameters lead to a better understanding of the role played by the
various factors upon the strength. Finally, the grain growth modelling can predict the structure
type that optimise a specific material property.
3.Residual-strain determination by least-square refinement of TOF neutron-diffraction
measurements
The complete macroscopic average strain tensor for a cold-rolled uranium plate was determined
by the least-squares refinement of inter-planar spacing for 19 Braggpolace reflections, as
determined from the neutron TOF measurements at LANSCE (Los Alamos). An annealed
uranium plate was used as a reference sample, thus providing reference interplanar spacings for
all 19 reflections. The mathematical background for the calculation of the average macroscopic
strain tensor as applied to the orthorhombic crystal symmetry and general triclinic sample
symmetry of the uranium sample is based on a recently proposed method to determine textureweighted strain orientation distribution function for arbitrary crystal and sample symmetries (N.
C. Popa and D. Balzar, J. Appl. Cryst. (2001) 34, 187-195). Similar measurements were
performed at the reactor IBR2 in Dubna on an extruded and strongly textured sample of
zirconium alloy of hexagonal crystal symmetry and cylindrical sample symmetry. The data
processing and determination of the strain- stress tensors according to the above mentioned
procedure are in progress.
EDUCATIONAL ACTIVITIES
Diploma Thesis: Ionel Mercioniu, "Effect on annealings on the properties of the hydroxyapatite
sputtered films” - Materials Science Faculty, Politechnica University
INTERNATIONAL COOPERATION:
1.Agreement of bilateral scientific cooperation between Rostock Universität, Fachbereich
Physik, Rostock, Germany and National Institute for Materials Physics ( NIMP ), Bucharest Magurele, Romania(2005-2008);projects:
Microstructural characterization of nanomaterials using electron microscopy (TEM, SEM,
EDX), atomic- and magnetic-force microscopy AFM/MFM methods (NIMP Coordinator : Dr. F.
Vasiliu).
Development of zirconium titanate based materials for microwave applications (NIMP
Coordinators : Dr. A. Ioachim, Dr. F. Vasiliu)
2.COST Action 540: Photocatalytic technologies and novel nanosurfaces materials -critical
issues "PHONASUM" (national coordinator Dr. F. Vasiliu)
3.Bilateral scientific cooperation ICV-CSIC Spain – INCDFM Romania (2003-2005) "Microstructure development of alumina and zirconia nano-composites with better
performances for technological applications in intermediate temperature SOFC ‘s". –
(Dr.N.Popescu-Pogrion)
78
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4. Bilateral scientific cooperation Sabanci University , Tuzla , Turkey – INCDFM Romania
(2003-2005) "Physics and Chemistry structural aspects of grain boundaries in doped α-Al2O3
and ZrO2"- (Dr.N.Popescu-Pogrion)
PAPERS PUBLISHED OR ACCEPTED FOR PUBLICATIONS IN 2005
1.D.Pantelica, F.Vasiliu, P.Ionescu, F.Negoita,“RBS, ERDA, TEM and SAED characterization
of sol-gel PZT films“, Nucl. Instr. Meth. B,240, p. 400-404, 2005
2.G.Roebben, O.Van der Biest, D.Scitti, A.Bellosi C.Sarbu and T,Lauwagie, “High temperature
stiffness and damping measurements to monitor the glassy intergranular phase in liquid-phasesintered silicon carbides”, J. Am. Ceram. Soc., vol.88[8] , 2152-2158, 005
3.N.C.Popa, D.Balzar, G.Stefanic, S.Vogel, D.Brown, M.Bourke, B.Clausen,“Residual-strain
determination by least-squares refinement of TOF neutron-diffraction measurements of
deformed uranium “Advances in X-Ray Analysis 47 CD-ROM, 2005
4.D.Balzar, N.C.Popa, “Analyzing microstructure by Rietveld refinement The Rigaku Journal,
22, 16-25 – invited paper 2005
5.N.C.Popa, D.Balzar, ”Size anisotropy and lognormal size distribution in the powder
diffraction whole pattern fitting” Acta Cryst. A61, C79, 2005
6.A.Ioachim, M.I.Toacsan, M.G.Banciu, L.Nedelcu, D.Ghetu, A.C.Dutu, F.Vasiliu,
H.V.Alexandru, C.Berbecaru, G.Stoica, P.Nita, “Ferroelectric Ba1-xSrxTiO3 materials for
electrically controlled microwave devices”, "Romanian Journal of Information Science and
Technology" accepted for publication 2005
7.R.Nicula, F.Turquier, M.Stir, V.Y.Kodash, J.R.Groza, E.Burkel, “Formation of quasicrystals
during field-activated sintering of nanostructured Al-Cu-Fe powders “Proceedings
SINTERING'05 (Grenoble), p. 184-187, 2005
8.R.Nicula, V.D.Cojocaru, M.Stir, J.Hennicke, E.Burkel,” High-energy ball-milling synthesis
and densification of Fe-Co alloy nanopowders” Proc. ISMANAM-2005, J. Alloys &
Compounds in press 2005
9.R.Nicula, F.Turquier, M.Stir, V.Y.Kodash, J.R.Groza, E.Burkel, “Quasicrystal phase
formation in Al-Cu-Fe nanopowders during field-activated”, Proc. ISMANAM-2005, J. Alloys
& Compounds in press 2005
10.M.Stir, R.Nicula, E.Burkel, “Pressure-temperature phase diagrams of pure and Ag-doped
nanocrystalline TiO2 photocatalysts” , J. Eur. Ceram. Soc. in press 2005
transition induced in Fe50Rh50 alloys by high pressure”J. Alloys & Compounds 386 8-11, 2005
12.R.Bercia, M.Tirnovan, C.Bercia, N.Popescu-Pogrion,” Electron microscopy investigations
on γ - irradiated dielectric” Surface and Interface Analysis, in press 2005
79
____________________________________________________________________________________________
13.M.Tirnovan, R.Bercia, S.Constantinescu, N.Popescu-Pogrion, “Study by mathematical
packing models of Y doped α-Al2O3”, J.Eur.Ceram.Soc in press 2005
14.R.Bercia, M.Tirnovan, N.Popescu-Pogrion, S.Constantinescu, M.A.Gulgun, R.Cannon,
M.Ruhle, “A correlation between the porosity and the grains growth in low Y doped alphaalumina. Mathematical model for low porosity.” J.Eur.Ceram.Soc. in press 2005
15.T.G.Berger, A.Leineweber, E.J.Mittemeijer, C.Sarbu, V.Duppel, P.Fischer,“The crystal
structure of the Pd6B phase”, accepted for publication in the April 2006 issue of Zeitschrift fuer
Kristallographie, dedicated to the 100-th birthday anniversary of Fritz Laves
CONFERENCES:
1.D.Pantelica, F.Vasiliu, P.Ionescu, F.Negoita, “RBS, ERDA, TEM and SAED characterization
of sol- gel PZT films“,XX Congress of the International Union of Crystallography, Florence,
Italy, 23-31 August, 2005
2.A.Ioachim, M.I.Toacsan, M.G.Banciu, L.Nedelcu, F.Vasiliu, D.Ghetu, C.A.Dutu, F.Lifei,
H.V.Alexandru, C.Berbecaru, G.Stoica, P.Nita, “BST ferroelectric materials for tunable
microwave devices”, Proceeding of the 36 th International Scientific Symposium of the Military
Equipment and Technologies Research Agency, Bucuresti, Romania, 26-27 mai 2005, Vol. I, p.
528-531, 2005
3.A.Ioachim, M.I.Toacsan, M.G.Banciu, L.Nedelcu, D.Ghetu, H.V.Alexandru, C.Berbecaru,
F.Vasiliu, P.Nita, R.Ramer, “Ferroelectric ceramics based on the BaO–SrO–TiO2 ternary
system for microwave applications”, IX Conference & Exhibition of the European Ceramic
Society, ECERS 2005, Portoroz, Slovenia, 2005
4.A.Ioachim, M.I.Toacsan, M.G.Banciu, L.Nedelcu, D.Ghetu, F.Vasiliu, H.V.Alexandru,
C.Berbecaru, G.Stoica, P.Nita, “Barium strontium titanate - based perovskite materials for
microwave applications”, International Conference on Perovskites – Properties and Potential
Applications, Dubendorf, Elvetia, 2005
5.A.Ioachim, M.I.Toacsan, M.G.Banciu, L.Nedelcu, D.Ghetu, A.C.Dutu, F.Vasiliu,
H.V.Alexandru, C.Berbecaru, G.Stoica, P.Nita, “Ba1-xSrxTiO3 ceramics for tunable microwave
Romania, Vol. 2, p. 277-280, 2005
6.L.Diamandescu, M.Feder, D.Tarabasanu–Mihaila, F.Vasiliu, L.Frunza, “Hydrothermal
synthesis and structural characterisation of xTiO -(1-x)α-Fe2O3 mixed oxide nanoparticles”,
Second Conference of the Coordination Action CONCORDE "CO-ordination of Nanostructured
Catalytic Oxides Research and Development in Europe" funded by the Sixth Framework
Programme of the European Union, Thessaloniki, Greece, January 26-28th 2006
7.F.Vasiliu "Overview of materials science research at the National Institute of Materials
Physics",(Invited lecture) Interdisciplinary seminar of the DAAD-PHD-Programme,
Univ.Rostock(Germany),2005
80
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8.R.Bercia, M.Tirnovan, N.Popescu-Pogrion “A mathematical correlation between some
accelerated methods in order to induce treeing in nano-dielectric layers”, ICTF13/ACSIN8
Congress, Stockholm, Sweden 19-23 June (CD-ROM), 2005
9.R.Bercia, M.Tirnovan, C.Bercia, N.Popescu-Pogrion,” Electron microscopy investigations on
γ - irradiated dielectric”, 11th European on Applications of Surface and Interface Analysis,
ECASIA 05, Vienna, Sep. (CD-ROM) 2005
81

HEAD: Dr. MIHAIL FLORIN LAZARESCU E

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