National Institute Of Materials Physics - Romania

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873 articles found

741. Radiation-induced donor generation in epitaxial and Cz diodes

Authors: Pintilie, I; Buda, M; Fretwurst, E; Honniger, F; Lindstrom, G; Stahl, J

Published: OCT 21 2005, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT, 552, 60, DOI: 10.1016/j.nima.2005.06.006

Thin epitaxial layers grown on Cz substrates (Epi) and high resistivity Cz diodes have been irradiated with fluences of 2 x 10(14) cm(-2) 24 GeV protons. It is shown that the differences in the changes observed in the effective doping concentration (N-eff) after irradiation of Epi silicon can be explained by the balance between the formation of two type of defects-a deep acceptor (the I center) and a shallow donor (the BD complex). The BD concentration in Epi material is evaluated to be similar to 1.3 x 10(12) cm(-3). (c) 2005 Elsevier B.V. All rights reserved.

742. Characterization of oxygen dimer-enriched silicon detectors

Authors: Boisvert, V; Lindstrom, JL; Moll, M; Murin, LI; Pintilie, I

Published: OCT 21 2005, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT, 552, 55, DOI: 10.1016/j.nima.2005.06.005

Various types of silicon material and silicon p(+)n diodes have been treated to increase the concentration of the oxygen dimer (02) defect. This was done by exposing the bulk material and the diodes to 6 MeV electrons at a temperature of about 350 degrees C. FTIR spectroscopy has been performed on the processed material confirming the formation of oxygen dimer defects in Czochralski silicon pieces. We also show results from TSC characterization on processed diodes. Finally, we investigated the influence of the dimer enrichment process on the depletion voltage of silicon diodes and performed 24 GeV/c proton irradiations to study the evolution of the macroscopic diode characteristics as a function of fluence. (c) 2005 Elsevier B.V. All rights reserved.

743. Effect of neutron irradiation on some piezoelectric properties of PZT type ceramics

Authors: Miclea, C; Tanasoiu, C; Miclea, CF; Spanulescu, I; Cioangher, M

Published: SEP 2005, JOURNAL DE PHYSIQUE IV, 128, 120, DOI: 10.1051/jp4:2005128018

Soft and hard type piezoceramic sintered samples were subjected to neutron irradiation in fluxes up to, 10(18) n/cm(2) and the changes of the basic properties brought about by irradiation were investigated. The results showed that intermediate irradiation levels of up to 10(15) n/cm(2) do not change significantly the properties, but higher levels changed them. Thus the electromechanical coupling factor, the dielectric permittivity and losses decreased while the mechanical quality factor increases with increasing neutron flux for both types of materials. Changes of the lattice constants a and c were also observed. The main defects produced by neutron irradiation are oxygen vacancies but they are not entirely responsible for the modification of the materials properties. Some other factors such as domain pinning and lattice deformation can contribute to the properties degradation.

744. (Zr, Sn)TiO4 thin films for application in electronics

Authors: Nistor, M; Gherendi, F; Magureanu, M; Mandache, NB; Ioachim, A; Banciu, MG; Nedelcu, L; Popescu, M; Sava, F; Alexandru, HV

Published: JUL 15 2005, APPLIED SURFACE SCIENCE, 247, 174, DOI: 10.1016/j.apsusc.2005.01.124

Thin films of zirconium tin titanate, (Zr0.8Sn0.2)TiO4 (ZST) were deposited using a pulsed electron beam source based on a channel-spark discharge for target ablation. An advanced degree of crystallization was obtained for the films deposited on alumina substrate post-annealed at 1000 degrees C. The crystalline lattice constants of the films are very close to those of the target material, which confirms the same stoichiometry in ZST films and in the bulk. (c) 2005 Elsevier B.V. All rights reserved.

745. Development of radiation tolerant semiconductor detectors for the Super-LHC

Authors: Moll, M; Adey, J; Al-Ajili, A; Alfieri, G; Allport, PP; Artuso, M; Assouak, S; Avset, BS; Barabash, L; Barcz, A; Bates, R; Biagi, SF; Bilei, GM; Bisello, D; Blue, A; Blumenau, A; Boisvert, V; Bolla, G; Bondarenko, G; Borchi, E; Borrello, L; Bortoletto, D; Boscardin, M; Bosisio, L; Bowcock, TJV; Brodbeck, TJ; Broz, J; Bruzzi, M; Brzozowski, A; Buda, M; Buhmann, P; Buttar, C; Campabadal, F; Campbell, D; Candelori, A; Casse, G; Cavallini, A; Charron, S; Chilingarov, A; Chren, D; Cindro, V; Collins, P; Coluccia, R; Contarato, D; Coutinho, J; Creanza, D; Cunningham, W; Dalla Betta, GF; Dawson, I; de Boer, W; De Palma, M; Demina, R; Dervan, P; Dittongo, S; Dolezal, Z; Dolgolenko, A; Eberlein, T; Eremin, V; Fall, C; Fasolo, F; Fizzotti, F; Fleta, C; Focardi, E; Forton, E; Fretwurst, E; Garcia, C; Garcia-Navarro, JE; Gaubas, E; Genest, MH; Gill, KA; Giolo, K; Glaser, M; Goessling, C; Golovine, V; Sevilla, SG; Gorelov, I; Goss, J; Bates, AG; Gregoire, G; Gregori, P; Grigoriev, E; Grillo, AA; Groza, A; Guskov, J; Haddad, L; Harkonen, J; Hauler, F; Hoeferkamp, M; Honniger, F; Horazdovsky, T; Horisberger, R; Horn, M; Houdayer, A; Hourahine, B; Hughes, G; Ilyashenko, I; Irmscher, K; Ivanov, A; Jarasiunas, K; Johansen, KMH; Jones, BK; Jones, R; Joram, C; Jungermann, L; Kalinina, E; Kaminski, P; Karpenko, A; Karpov, A; Kazlauskiene, V; Kazukauskas, V; Khivrich, V; Khomenkov, V; Kierstead, J; Klaiber-Lodewigs, J; Klingenberga, R; Kodys, P; Kohout, Z; Korjenevski, S; Koski, M; Kozlowski, R; Kozodaev, M; Kramberger, G; Krasel, O; Kuznetsov, A; Kwan, S; Lagomarsino, S; Lassila-Perini, K; Lastovetsky, V; Latino, G; Lazanu, S; Lazanu, I; Lebedev, A; Lebel, C; Leinonen, K; Leroy, C; Li, Z; Lindstrom, G; Linhart, V; Litovchenko, A; Litovchenko, P; Lo Giudice, A; Lozano, M; Luczynski, Z; Luukka, P; Macchiolo, A; Makarenko, LF; Mandic, I; Manfredotti, C; Manna, N; Marti i Garcia, S; Marunko, S; Mathieson, K; Melone, J; Menichelli, D; Messineo, A; Metcalfe, J; Miglio, S; Mikuz, M; Miyamoto, J; Monakhov, E; Moscatelli, F; Naoumov, D; Nossarzewska-Orlowska, E; Nysten, J; Olivera, P; OShea, V; Palvialnen, T; Paolini, C; Parkes, C; Passeri, D; Pein, U; Pellegrini, G; Perera, L; Petasecca, K; Piemonte, C; Pignatel, GU; Pinho, N; Pintilie, I; Pintilie, L; Polivtsev, L; Polozov, P; Popa, A; Popule, J; Pospisil, S; Pozza, A; Radicci, V; Rafi, JM; Rando, R; Roeder, R; Rohe, T; Ronchin, S; Rott, C; Roy, A; Ruzin, A; Sadrozinski, HFW; Sakalauskas, S; Scaringella, M; Schiavulli, L; Schnetzer, S; Schumm, B; Sciortino, S; Scorzoni, A; Segneri, G; Seidel, S; Seiden, A; Sellberg, G; Sellin, P; Sentenac, D; Shipsey, I; Sicho, P; Sloan, T; Solar, M; Son, S; Sopko, B; Sopko, V; Spencer, N; Stahl, J; Stolze, D; Stone, R; Storasta, J; Strokan, N; Sudzius, M; Surma, B; Suvorov, A; Svensson, BG; Tipton, P; Tomasek, M; Tsvetkov, A; Tuominen, E; Tuovinen, E; Tuuva, T; Tylchin, M; Uebersee, H; Uher, J; Ullan, M; Vaitkus, JV; Velthuis, J; Verbitskaya, E; Vrba, V; Wagner, G; Wilhelm, I; Worm, S; Wright, V; Wunstorf, R; Yiuri, Y; Zabierowski, P; Zaluzhny, A; Zavrtanik, M; Zen, M; Zhukov, V; Zorzi, N

Published: JUL 1 2005, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT, 546, 107, DOI: 10.1016/j.nima.2005.03.044

The envisaged upgrade of the Large Hadron Collider (LHC) at CERN towards the Super-LHC (SLHC) with a 10 times increased luminosity of 10(35) cm(-2) s(-1) Will present severe challenges for the tracking detectors of the SLHC experiments. Unprecedented high radiation levels and track densities and a reduced bunch crossing time in the order of 10 ns as well as the need for cost effective detectors have called for an intensive R&D program. The CERN RD50 collaboration "Development of Radiation Hard Semiconductor Devices for Very High Luminosity Colliders" is working on the development of semiconductor sensors matching the requirements of the SLHC. Sensors based on defect engineered silicon like Czochralski, epitaxial and oxygen enriched silicon have been developed. With 3D, Semi-3D and thin detectors new detector concepts have been evaluated and a study on the use of standard and oxygen enriched p-type silicon detectors revealed a promising approach for radiation tolerant cost effective devices. These and other most recent advancements of the RD50 collaboration are presented. (c) 2005 Elsevier B.V. All rights reserved.

746. Micro-structure and magnetic properties of Fe-Cu nanocomposites for anisotropic permanent magnets

Authors: Kuncser, V; Valeanu, M; Lifei, F; Predoi, D; Jianu, A; Kappel, W; Codescu, M; Patroi, E; Pasuk, I; Bulinski, M; Filoti, G

Published: MAY 31 2005, JOURNAL OF ALLOYS AND COMPOUNDS, 395, 6, DOI: 10.1016/j.jallcom.2004.11.059

Melt spun ribbons of FexCu100-x were obtained by different procedures, in order to maximize the dispersion of the Fe atoms in the Cu matrix. Subsequent thermal and mechanical treatments were used for a controlled crystallization process of the soft magnetic phase. A detailed analysis of structural aspects and crystallization dynamics and their relation with the magnetic behavior of the Fe-Cu ribbons has been obtained via Mossbauer spectroscopy, X-ray diffraction (XRD) and magnetic measurements. In order to obtain composite permanent magnets with shape anisotropy, the optimal conditions and the suitable processing were established. © 2004 Elsevier B.V. All rights reserved.

747. Space-charge-limited current involving carrier injection into impurity bands of high-k insulators

Authors: Goldenblum, A; Pintilie, I; Buda, M; Popa, A; Botila, T; Dimoulas, A; Vellianitis, G

Published: MAY 16 2005, APPLIED PHYSICS LETTERS, 86, DOI: 10.1063/1.1935045

Photoelectrical measurements have shown that the current flow through La2Hf2O7 and LaAlO3 high-k insulator layers deposited on silicon takes place via impurity channels. A space charge limited current is evidenced, for different insulator thicknesses and temperatures, by the square law dependence of current versus voltage. The analysis demonstrates that this space charge limited (SCL) current in thin insulator films can be explained only by the presence of impurity channels situated near the Fermi level of the injecting contact. Many other aspects related to the SCL current behavior were found. (c) 2005 American Institute of Physics.

748. Polarization reversal and capacitance-voltage characteristic of epitaxial Pb(Zr,Ti)O-3 layers

Authors: Pintilie, L; Lisca, M; Alexe, M

Published: MAY 9 2005, APPLIED PHYSICS LETTERS, 86, DOI: 10.1063/1.1926403

Capacitance-voltage (C-V) measurements were performed on epitaxial layers of PbsZr(0.2)Ti(0.8)dO(3) (PZT) with top and bottom SrRuO3 (SRO) electrodes. It is shown that the sharp capacitance peak/discontinuity which is present in the C-V characteristics at different frequencies is directly associated with the polarization reversal. The ferroelectric film is assumed as a large band-gap semiconductor with Schottky contacts at the metal-ferroelectric interfaces. The capacitance discontinuity at the reversal scoercived voltage is associated with a discontinuity in the built-in potential at the PZT/ SRO interfaces. The C-V characteristics for voltage ranges outside the coercive values can be used to extract the free carrier concentrations as in the case of Schottky metal-semiconductor contacts. The carrier concentration was found to be (2-4) x 10(18) cm(-3), independent of measuring frequency and temperature up to 1 MHz and 170 degrees C, respectively, suggesting completely ionized shallow impurities. (c) 2005 American Institute of Physics.

749. Nickel-doped (Zr-0.8, Sn-0.2)TiO4 for microwave and millimeter-wave applications

Authors: Ioachim, A; Banciu, MG; Toacsan, MI; Nedelcu, L; Ghetu, D; Alexandru, HV; Stoica, G; Annino, G; Cassettari, M; Martinelli, M

Published: APR 25 2005, MATERIALS SCIENCE AND ENGINEERING B-SOLID STATE MATERIALS FOR ADVANCED TECHNOLOGY, 118, 209, DOI: 10.1016/j.mseb.2004.12.071

(Zr-0.8, Sn-0.2)TiO4 ternary compounds (ZST) have been prepared by conventional solid-state reaction from raw materials. The effects of such sintering parameters as sintering temperature, sintering time, and NiO addition on structural and dielectric properties were investigated. The material exhibits a dielectric constant epsilon(r), similar to 36.0 and high values of the product Qf of the intrinsic quality factor Q and the frequency f from 32,170 to 50,000 at microwave frequencies. The dielectric loss tan delta values of ZST ceramics are decreased by low-level doping of NiO, while the temperature coefficient of the resonance frequency tau(f) takes values in the range -2 to +4ppm/degrees C. Investigations on whispering gallery modes revealed low dielectric loss in millimetre-wave domain. An intrinsic quality factor of 480 was measured at 115.6GHz. Dielectric resonators and substrates of ZST material were manufactured. The dielectric properties make the ZST material very attractive to microwave and millimeter-wave applications, such as dielectric resonators, filters, planar antennas, hybrid microwave integrated circuits, etc. (c) 2005 Elsevier B.V. All rights reserved.

750. Ferroelectric solid solutions (Ba,Sr)TiO3 for microwave applications

Authors: Alexandru, HV; Berbecaru, C; Stanculescu, F; Ioachim, A; Banciu, MG; Toacsen, MI; Nedelcu, L; Ghetu, D; Stoica, G

Published: APR 25 2005, MATERIALS SCIENCE AND ENGINEERING B-SOLID STATE MATERIALS FOR ADVANCED TECHNOLOGY, 118, 96, DOI: 10.1016/j.mseb.2004.12.070

There is an increasing demand of high permittivity ferroelectric materials in microwave devices. Particularly, the Ba1-xSrxTiO3 system (BST), presents a major interest for electrically controlled devices, such as tunable filters, steerable antennas, phase shifters, varactors, etc. [F. De Flaviis, N.G. Alexopoulos, O.M. Stafsudd, IEEE Trans. Microw. Theory Tech., MTT-45 (6) (1997) 963-969]. Solid solutions with X=25, 50, 75, 90% were prepared by standard ceramic technology (solid state reaction) and sintered at 1230 and 1260 degrees C. The temperature dependence of permittivity and of losses at low frequency (1 kHz) has shown interesting results [A. loachim, M.I. Toacsen, M.G. Banciu, L. Nedelcu, D. Ghetu, H.V. Alexandru, C. Berbecaru, G. Stoica, Proceedings on the XVII International Conference on Electromagnetic Fields and Materials, Warszawa, May 2004, pp. 78-82]. The unit cell volume depends linearly on the Sr content ohm (angstrom(3)) = 61.1 + 3.6X (estimated from Ref. [D. Roy, S. D. Krupandihi, Appl. Phys. Lett. 62 (1993) 1056-1058]). The measured densities of our samples p (g/cm(3)); approximate to 5.50 - 1.00X, represent about 92% of the X-ray estimated density p (g/cm(3)) approximate to 5.99 - 0.99X. Microwave measurements around 1 GHz show substantial decrease of the permittivity from about 1600 to 200 and also of the losses from 0.8% to less than 0.15% with the Sr concentration increase, X = 50-90%. It is concluded that sintering temperature has to be increased for samples of high Sr concentration. Moreover, the addition of MgO and MnO2, 1 wt.% each, improve sintering conditions and decreases the microwave losses. Experimental data show an approximate linear decrease of the Curie point, versus X strontium concentration, according to the formula: T-C (degrees C) approximate to 120-360X. Room temperature permittivity and dielectric loss have been measured in microwaves range using the Hakki-Coleman method. (c) 2005 Elsevier B.V All rights reserved.