National Institute Of Materials Physics - Romania

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860 articles found

731. (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.

732. 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.

733. 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.

734. 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.

735. 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.

736. 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.

737. 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.

738. Doped versus pure TGS crystals

Authors: Berbecaru, C; Alexandru, HV; Pintilie, L; Dutu, A; Logofatu, B; Radulescu, RC

Published: APR 25 2005, MATERIALS SCIENCE AND ENGINEERING B-SOLID STATE MATERIALS FOR ADVANCED TECHNOLOGY, 118, 146, DOI: 10.1016/j.mseb.2004.12.069

Pure and L- or D-alanime doped triglycine sulphate crystals (TGS) where grown in paraelectric phase around 52 degrees C. Doped crystals show lower and reproducible permittivities (crossing down the Curie point) and much lower losses versus pure crystals. Higher figures of merit have to be expected for highly doped crystals, suitable for IR detection. A remarkable difference of the experimental curves was noticed in the temperature dependence of the pyroelectric coefficients (p = dP(S)/dT) for L- and D-alanine doped samples. This fact suggests a non-equivalent L/D-alanine dopant substitution of the glycine group GI in the host lattice. Spontaneous polarization was calculated by integration of pyroelectric current data, and separately from the hysteresis loops recorded on a large temperature range, using Sawyer-Tower (phase compensated) circuit. Polarization values estimated from the two method compare reasonable well, except the temperature range in the proximity of the Curie point. lnternal bias field of similar to 1 kV/cm, induced by L-alanine dopant, stabilizes the polarization components P+ and P- opposite directions, with a peculiar dependence on the ac electric field. (c) 2005 Elsevier B.V. All rights reserved.

739. Radiation-hard semiconductor detectors for SuperLHC

Authors: Bruzzi, M; Adey, J; Al-Ajili, A; Alexandrov, P; Alfieri, G; Allport, PP; Andreazza, A; Artuso, M; Assouak, S; Avset, BS; Barabash, L; Baranova, E; Barcz, A; Basile, A; Bates, R; Belova, N; Biagi, SF; Bilei, GM; Bisello, D; Blue, A; Blumenau, B; Boisvert, V; Bolla, G; Bondarenko, G; Borchi, E; Borrello, L; Bortoletto, D; Boscardin, M; Bosisio, L; Bowcock, TJV; Brodbeck, TJ; Broz, J; Brukhanov, A; Brzozowski, A; Buda, M; Buhmann, P; Buttar, C; Campabadal, F; Campbell, D; Candelori, A; Casse, G; Cavallini, A; Chilingarov, A; Chren, D; Cindro, V; Citterio, M; Collins, P; Coluccia, R; Contarato, D; Coutinho, J; Creanza, D; Cunningham, W; Cvetkov, V; Dalla Betta, GF; Davies, G; Dawson, I; de Boer, W; De Palma, M; Demina, R; Dervan, P; Dierlamm, A; Dittongo, S; Dobrzanski, L; Dolezal, Z; Dolgolenko, A; Eberlein, T; Eremin, V; Fall, C; Fasolo, F; Ferbel, T; Fizzotti, F; Fleta, C; Focardi, E; Forton, E; Franchenko, S; Fretwurst, E; Gamaz, F; 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; Gouldwell, A; Gregoire, G; Gregori, P; Grigoriev, E; Grigson, C; Grillo, A; Groza, A; Guskov, J; Haddad, L; Harkonen, J; Harding, R; Hauler, F; Hayama, S; Hoeferkamp, M; Honniger, F; Horazdovsky, T; Horisberger, R; Horn, M; Houdayer, A; Hourahine, B; Hruban, A; Hughes, G; Ilyashenko, I; Irmscher, K; Ivanov, A; Jarasiunas, K; Jin, T; 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; Kleverman, M; Klingenberg, R; Kodys, P; Kohout, Z; Korjenevski, S; Kowalik, A; Kozlowski, R; Kozodaev, M; Kramberger, G; Krasel, O; Kuznetsov, A; Kwan, S; Lagomarsino, S; Lari, T; Lassila-Perini, K; Lastovetsky, V; Latino, G; Latushkin, S; Lazanu, S; Lazanu, I; Lebel, C; Leinonen, K; Leroy, C; Li, Z; Lindstrom, G; Lindstrom, L; Linhart, V; Litovchenko, A; Litovchenko, P; Litvinov, V; Lo Giudice, A; Lozano, M; Luczynski, Z; Luukka, P; Macchiolo, A; Mainwood, A; Makarenko, LF; Mandic, I; Manfredotti, C; Garcia, SM; Marunko, S; Mathieson, K; Mozzanti, A; Melone, J; Menichelli, D; Meroni, C; Messineo, A; Miglio, S; Mikuz, M; Miyamoto, J; Moll, M; Monakhov, E; Moscatelli, F; Murin, L; Nava, F; Naoumov, D; Nossarzewska-Orlowska, E; Nummela, S; Nysten, J; Olivero, P; Oshea, V; Palviainen, T; Paolini, C; Parkes, C; Passeri, D; Pein, U; Pellegrini, G; Perera, L; Petasecca, M; Piatkowski, B; Piemonte, C; Pignatel, GU; Pinho, N; Pintilie, I; Pintilie, L; Polivtsev, L; Polozov, P; Popa, AI; Popule, J; Pospisil, S; Pucker, G; Radicci, V; Rafi, JM; Ragusa, F; Rahman, M; Rando, R; Roeder, R; Rohe, T; Ronchin, S; Rott, C; Roy, P; Roy, A; Ruzin, A; Ryazanov, 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; Spencer, N; Stahl, J; Stavitski, I; Stolze, D; Stone, R; Storasta, J; Strokan, N; Strupinski, W; Sudzius, M; Surma, B; Suuronen, J; Suvorov, A; Svensson, BG; Tipton, P; Tomasek, M; Troncon, C; Tsvetkov, A; Tuominen, E; Tuovinen, E; Tuuva, T; Tylchin, M; Uebersee, H; Uher, J; Ullan, M; Vaitkus, JV; Vanni, P; Velthuis, J; Verzellesi, G; Verbitskaya, E; Vrba, V; Wagner, G; Wilhelm, I; Worm, S; Wright, V; Wunstorf, R; Zablerowski, P; Zaluzhny, A; Zavrtanik, M; Zen, M; Zhukov, V; Zorzi, N

Published: APR 1 2005, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT, 541, 201, DOI: 10.1016/j.nima.2005.01.056

An option of increasing the luminosity of the Large Hadron Collider (LHC) at CERN to 1035 cm-2 s-1 has been envisaged to extend the physics reach of the machine. An efficient tracking down to a few centimetres from the interaction point will be required to exploit the physics potential of the upgraded LHC. As a consequence, the semiconductor detectors close to the interaction region will receive severe doses of fast hadron irradiation and the inner tracker detectors will need to survive fast hadron fluences of up to above 1016cm-2. The CERN-RD50 project "Development of Radiation Hard Semiconductor Devices for Very High Luminosity Colliders" has been established in 2002 to explore detector materials and technologies that will allow to operate devices up to, or beyond, this limit. The strategies followed by RD50 to enhance the radiation tolerance include the development of new or defect engineered detector materials (SiC, GaN, Czochralski and epitaxial silicon, oxygen enriched Float Zone silicon), the improvement of present detector designs and the understanding of the microscopic defects causing the degradation of the irradiated detectors. The latest advancements within the RD50 collaboration on radiation hard semiconductor detectors will be reviewed and discussed in this work. 2005 Published by Elsevier B.V.

740. Soft ferrite materials for magnetic temperature transducers and applications

Authors: Miclea, C; Tanasoiu, C; Miclea, CF; Gheorghiu, A; Tanasoiu, V

Published: APR 2005, JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS, 290, 1509, DOI: 10.1016/j.jmmm.2004.11.561

Soft ferrites in the CuZnTi system, having the formula Cu1-xZnxTiyFe2-4O4, with 0.50 <= x <= 0.60 and 0.00 <= y <= 0.05 were investigated as a function of composition, sintering temperature and cooling speed, in order to obtain materials with controlled T-C and very high change rate of permeability with temperature around their T-C. The effect of Zn and Ti additions was a drastic change of the Curie temperature with about 10-12 degrees C for each atomic percent of Zn and Ti introduced into the spinel lattice while the cooling speed changed the behaviour of magnetic permeability with temperature around the Curie point. An application using such magnetic temperature sensors for a thermostat is presented. (c) 2004 Elsevier B.V. All rights reserved.