National Institute Of Materials Physics - Romania

Publications

838 articles found

771. Advanced electroceramic materials for electrotechnical applications

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

Published: MAR 2002, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 4, 58, DOI:

Advanced electroceramics have played a critical role in the development of new and modem technologies such as computers, telecomunications and aerospace and they will continue to play the leading role in the technology of the future. The present report presents and discusses a number of advanced electroceramic materials with special references to their specific properties that make them indispensable in a large area of applications. The materials discussed include cobalt-mangan oxides used as negative temperature coefficient thermistors, semiconducting doped barium titanate used for positive temperature coefficient thermistors with large applications in thermal protections and piezoelectric electroceramics of PZT type, which find new application as ceramic transducers and sensors in biomedical and aerospace industries or as simply buzzers, filters, igniters, ultrasonic cleaners, towed array sonars, medical imaging system, ink-jet printing heads, camera shuttlers, positioners for optical systems, micromotors and actuators. Such advanced electroceramic materials are extremely useful for the future sophisticated technologies such as heads for magnetic recording, scanning tunneling microscope, sensors for antilock braking systems, ultrasonic bone-healing devices and some other biomedical applications.

772. Preparation of BaTi4O9 from oxalates

Authors: Cernea, M; Chirtop, E; Neacsu, D; Pasuk, I; Iordanescu, S

Published: FEB 2002, JOURNAL OF THE AMERICAN CERAMIC SOCIETY, 85, 503, DOI:

A barium titanate precursor with a barium:titanium ratio of 1:4 was prepared by controlled coprecipitation of mixed barium and titanium species with an ammonium oxalate aqueous solution at pH 7. The results of thermal analysis and IR measurement show that the obtained precursor is a mixture of BaC2O4.0.5H(2)O and TiO(OH)(2).1.5H(2)O in a molar ratio of 1:4. Crystallized BaTi4O9 was obtained by the thermal decomposition of a precipitate precursor at 1300degreesC for 2 h in air. The dimensions of the powder calcined at 1000degreesC are between 100 and 300 nm. The grain dimensions of the sintered sample for 2 h at 1300degreesC are of the order of 10 to 30 mum. Dielectric properties of disk-shaped sintered specimens in the microwave frequency region were measured using the TE011 mode. Excellent microwave characteristics for BaTi4O9-epsilon = 38 +/- 0.5, Q = 3800-4000 at 6-7 GHz and tau(f) = 11 +/- 0.7 ppm/degreesC-were found.

773. Thermally stimulated current method applied to highly irradiated silicon diodes

Authors: Pintilie, I; Tivarus, C; Pintilie, L; Moll, M; Fretwurst, E; Lindstroem, G

Published: JAN 11 2002, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT, 476, 657, DOI: 10.1016/S0168-9002(01)01654-0

We propose an improved method for the analysis of Thermally Stimulated Currents (TSC) measured on highly irradiated silicon diodes. The proposed TSC formula for the evaluation of a set of TSC spectra obtained with different reverse biases leads not only to the concentration of electron and hole traps visible in the spectra but also gives an estimation for the concentration of defects which not give rise to a peak in the 30-220 K TSC temperature range (very shallow or very deep levels). The method is applied to a diode irradiated with a neutron fluence of phi(n) = 1.82 x 10(13) n/cm(2). (C) 2002 Published by Elsevier Science B.V.

774. Pyroelectric properties of alanine doped TGS single crystalline thick films under constant electric stress

Authors: Pintilie, L; Matei, I; Pintilie, L

Published: 2002, FERROELECTRIC THIN FILMS X, 688, 228, DOI:

Pyroelectric properties of triglycine sulfate (TGS) thick films, separately doped with L and D alanine were investigated. Internal bias field of about 1 kV/cm, induced by the two dopants, stabilize the polarization in the opposite direction on the ferroelectric axis. Pyroelectric current (under constant stress) was recorded with a computer controlled Keithley 6517 electrometer, crossing up and down the Curie point. A reverse external electric field was applied on doped materials during heating, crossing up the Curie point. It is shown that the pyroelectric coefficient can be increased about four times at room temperature under un optimized DC electric field applied on the pyroelectric wafer.

775. Deep levels in as-grown 4H-SiC epitaxial layers and their correlation with CVD parameters

Authors: Pintilie, I; Pintilie, L; Irmscher, K; Thomas, B

Published: 2002, SILICON CARBIDE AND RELATED MATERIALS - 2002, 433-4, 466, DOI:

Nitrogen doped 4H-SiC epitaxial layers grown by hot-wall chemical vapor deposition were investigated by deep level transient spectroscopy in the as-grown state. Besides the Z(1,2) defect level at E-C - 0.66 eV, that seems to be omnipresent, four other electron traps labeled IL1 to IL4 With ionization energies between 0.87 and 1.31 eV could be detected. The dependence of the deep level concentrations on the incorporated N concentration ranging from few 10(14) to Some 10(15) cm(-3) and the C/Si ratio (1.2divided by3) was examined. The concentration of both Z(1,2) and IL1 increases with increasing N doping. For medium C/Si ratios this dependence is linear for Z(1,2) and quadratic for IL1. High C/Si ratios enhance the formation of Z(1,2) while they suppress that of IL1. These results suggest a complex of interstitial C and N on carbon site (C-i-N-C) for Z(1,2) and a nitrogen pair (N-C-N-i) for IL1. However, other possibilities like Si vacancy related defects cannot be ruled out at present.

776. Field effect controlled photoresistors based on chemically deposited PbS films

Authors: Pentia, E; Pintilie, L; Matei, I; Pintilie, I

Published: 2002, PROGRESS IN SEMICONDUCTOR MATERIALS FOR OPTOELECTRONIC APPLICATIONS, 692, 446, DOI:

MOS-like structures were obtained by chemical deposition of a polycrystalline PbS thin film on top of a silicon dioxide/Si substrate. Gold ohmic electrodes in coplanar configuration were subsequently deposited by vacuum evaporation on PbS surface (drain and source electrodes). The gate aluminum electrode was deposited on the back of the Si substrate. The dependence of the photoconductive signal, generated in the PbS film, on the gate voltage was studied for wavelengths ranging between 800 nm and 3000 nm at room temperature as well as at low temperatures. It was found that the relative variation of the signal could be as high as 50% for gate voltages ranging between -30 V and +30 V. Two possible mechanisms are proposed to explain the signal variation with the gate voltage: 1) Variation of the depleted region's thickness in the PbS film, that leads to a variation of the conduction channel's resistance (the reference resistance called, also, the dark resistance), 2) The possible variation of the majority carriers (holes) life-time due to the electron blocking at the PbS/oxide interface when positive gate voltages are applied on the back electrode. Integrated IR detectors with controlled sensitivity in the 800-3000 nm range can be manufactured at a relatively low cost using the PbS/oxide/Si MOS-like structure.

777. Deep level defects in sublimation-grown 6H silicon carbide investigated by DLTS and EPR

Authors: Irmscher, K; Pintilie, I; Pintilie, L; Schulz, D

Published: DEC 2001, PHYSICA B-CONDENSED MATTER, 308, 733, DOI: 10.1016/S0921-4526(01)00887-0

6H-SiC bulk single crystals grown by physical vapor transport (PVT) were investigated by deep-level transient spectroscopy (DLTS) and electron paramagnetic resonance (EPR). One of the observed deep level defects was identified as isolated tungsten on Si sites by EPR. The electron spin of 1 could be explained by W5+ (5d(1)). This is equivalent to the single positive charge state of a double donor when taking into account the Fermi level position in the n-type samples. The interpretation is also consistent with the DLTS detection of a W related deep level which showed a behavior of the capture of electrons and holes that hints at a double donor. In addition a tantalum related deep level is tentatively discussed. W and Ta were incorporated on electrically active sites in 6H-SiC only in low concentrations (2-4 x 10(4) cm(-3)) during crystal growth by PVT. (C) 2001 Elsevier Science B.V. All rights reserved.

778. Radiation hard silicon detectors - developments by the RD48 (ROSE) collaboration

Authors: Lindstrom, G; Ahmed, M; Albergo, S; Allport, P; Anderson, D; Andricek, L; Angarano, MM; Augelli, V; Bacchetta, N; Bartalini, P; Bates, R; Biggeri, U; Bilei, GM; Bisello, D; Boemi, D; Borchi, E; Botila, T; Brodbeck, TJ; Bruzzi, M; Budzynski, T; Burger, P; Campabadal, F; Casse, G; Catacchini, E; Chilingarov, A; Ciampolini, P; Cindro, V; Costa, MJ; Creanza, D; Clauws, P; Da Via, C; Davies, G; De Boer, W; Dell'Orso, R; De Palma, M; Dezillie, B; Eremin, V; Evrard, O; Fallica, G; Fanourakis, G; Feick, H; Focardi, E; Fonseca, L; Fretwurst, E; Fuster, J; Gabathuler, K; Glaser, M; Grabiec, P; Grigoriev, E; Hall, G; Hanlon, M; Hauler, F; Heising, S; Holmes-Siedle, A; Horisberger, R; Hughes, G; Huhtinen, M; Ilyashenko, I; Ivanov, A; Jones, BK; Jungermann, L; Kaminsky, A; Kohout, Z; Kramberger, G; Kuhnke, M; Kwan, S; Lemeilleur, F; Leroy, C; Letheren, M; Li, Z; Ligonzo, T; Linhart, V; Litovchenko, P; Loukas, D; Lozano, M; Luczynski, Z; Lutz, G; MacEvoy, B; Manolopoulos, S; Markou, A; Martinez, C; Messineo, A; Mikuz, M; Moll, M; Nossarzewska, E; Ottaviani, G; Oshea, V; Parrini, G; Passeri, D; Petre, D; Pickford, A; Pintilie, I; Pintilie, L; Pospisil, S; Potenza, R; Raine, C; Rafi, JM; Ratoff, PN; Richter, RH; Riedler, P; Roe, S; Roy, P; Ruzin, A; Ryazanov, AI; Santocchia, A; Schiavulli, L; Sicho, P; Siotis, I; Sloan, T; Slysz, W; Smith, K; Solanky, M; Sopko, B; Stolze, K; Avset, BS; Svensson, B; Tivarus, C; Tonelli, G; Tricomi, A; Tzamarias, S; Valvo, G; Vasilescu, A; Vayaki, A; Verbitskaya, E; Verdini, P; Vrba, V; Watts, S; Weber, ER; Wegrzecki, M; Wegrzecka, I; Weilhammer, P; Wheadon, R; Wilburn, C; Wilhelm, I; Wunstorf, R; Wustenfeld, J; Wyss, J; Zankel, K; Zabierowski, P; Zontar, D

Published: JUL 1 2001, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT, 466, 326, DOI: 10.1016/S0168-9002(01)00560-5

The RD48 (ROSE) collaboration has succeeded to develop radiation hard silicon detectors. capable to withstand the harsh hadron fluences in the tracking areas of LHC experiments. In order to reach this objective, a defect engineering technique was employed resulting in the development of Oxygen enriched FZ silicon (DOFZ), ensuring the necessary O-enrichment of about 2 x 10(17) O/cm(3) in the normal detector processing. Systematic investigations have been carried out on various standard and oxygenated silicon diodes with neutron, proton and pion irradiation up to a fluence of 5 x 10(14)cm(-2) (1 MeV neutron equivalent). Major focus is on the changes of the effective doping concentration (depletion voltage). Other aspects (reverse current, charge collection) are covered too and the appreciable benefits obtained with DOFZ silicon in radiation tolerance for charged hadrons are outlined. The results are reliably described by the "Hamburg model": its application to LHC experimental conditions is shown, demonstrating the superiority of the defect engineered silicon. Microscopic aspects of damage effects are also discussed. including differences due to charged and neutral hadron irradiation. (C) 2001 Elsevier Science B.V. All rights reserved.

779. Developments for radiation hard silicon detectors by defect engineering - results by the CERN RD48 (ROSE) Collaboration

Authors: Lindstrom, G; Ahmed, M; Albergo, S; Allport, P; Anderson, D; Andricek, L; Angarano, MM; Augelli, V; Bacchetta, N; Bartalini, P; Bates, R; Biggeri, U; Bilei, GM; Bisello, D; Boemi, D; Borchi, E; Botila, T; Brodbeck, TJ; Bruzzi, M; Budzynski, T; Burger, P; Campabadal, F; Casse, G; Catacchini, E; Chilingarov, A; Ciampolini, P; Cindro, V; Costa, MJ; Creanza, D; Clauws, P; Da Via, C; Davies, G; De Boer, W; Dell'Orso, R; De Palma, M; Dezillie, B; Eremin, V; Evrard, O; Fallica, G; Fanourakis, G; Feick, H; Focardi, E; Fonseca, L; Fretwurst, E; Fuster, J; Gabathuler, K; Glaser, M; Grabiec, P; Grigoriev, E; Hall, G; Hanlon, M; Hauler, F; Heising, S; Holmes-Siedle, A; Horisberger, R; Hughes, G; Huhtinen, M; Ilyashenko, I; Ivanov, A; Jones, BK; Jungermann, L; Kaminsky, A; Kohout, Z; Kramberger, G; Kuhnke, M; Kwan, S; Lemeilleur, F; Leroy, C; Letheren, M; Li, Z; Ligonzo, T; Linhart, V; Litovchenko, P; Loukas, D; Lozano, M; Luczynski, Z; Lutz, G; MacEvoy, B; Manolopoulos, S; Markou, A; Martinez, C; Messineo, A; Mikuz, M; Moll, M; Nossarzewska, E; Ottaviani, G; Oshea, V; Parrini, G; Passeri, D; Petre, D; Pickford, A; Pintilie, I; Pintilie, L; Pospisil, S; Potenza, R; Radicci, V; Raine, C; Rafi, JM; Ratoff, PN; Richter, RH; Riedler, P; Roe, S; Roy, P; Ruzin, A; Ryazanov, AI; Santocchia, A; Schiavulli, L; Sicho, P; Siotis, I; Sloan, T; Slysz, W; Smith, K; Solanky, M; Sopko, B; Stolze, K; Avset, BS; Svensson, B; Tivarus, C; Tonelli, G; Tricomi, A; Tzamarias, S; Valvo, G; Vasilescu, A; Vayaki, A; Verbitskaya, E; Verdini, P; Vrba, V; Watts, S; Weber, ER; Wegrzecki, M; Wegrzecka, I; Weilhammer, P; Wheadon, R; Wilburn, C; Wilhelm, I; Wunstorf, R; Wustenfeld, J; Wyss, J; Zankel, K; Zabierowski, P; Zontar, D

Published: JUN 1 2001, NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT, 465, 69, DOI: 10.1016/S0168-9002(01)00347-3

This report summarises the final results obtained by the RD48 collaboration. The emphasis is on the more practical aspects directly relevant for LHC applications. The report is based on the comprehensive survey given in the 1999 status report (RD48 3rd Status Report, CERN/LHCC 2000-009, December 1999), a recent conference report (Lindstrom et al, (RD48), and some latest experimental results. Additional data have been reported in the last ROSE workshop (5th ROSE workshop, CERN, CERN/LEB 2000-005), A compilation of all RD48 internal reports and a full publication list can be found on the RD48 homepage (http://cern.ch/RD48/). The success of the oxygen enrichment of FZ-silicon as a highly powerful defect engineering technique and its optimisation with various commercial manufacturers are reported. The focus is on the changes of the effective doping concentration (depletion voltage). The RD48 model for the dependence of radiation effects on fluence, temperature and operational time is verified: projections to operational scenarios for main LHC experiments demonstrate vital benefits. Progress in the microscopic understanding of damage effects as well as the application of defect kinetics models and device modelling for the prediction of the macroscopic behaviour was also been achieved but will not be covered in detail. (C) 2001 Elsevier Science B.V. All rights reserved.

780. Chemically prepared nanocrystalline PbS thin films

Authors: Pentia, E; Pintilie, L; Matei, I; Botila, T; Ozbay, E

Published: JUN 2001, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 3, 530, DOI:

PbS nanocrystalline thin films were prepared by Chemical Bath Deposition (CBD) technique. A comparative study between "standard" and "nanocrystalline" PbS thin films was performed. We denoted "standard" the PbS film with a good photosensitivity for to use as IR detector. This film was deposited after 1 hour from chemical bath containing reducing agent and Bi ions as doping element. The "nanocrystalline" film was obtained at shorter reaction time (after 17 minutes) from reducing bath without doping element. The other parameters: concentration of the reactants, pH, temperature were kept constant for the all depositions. The morphological properties of the films were determined by SEM analysis. Also, the electrical and photoelectrical behaviors were investigated for the both types of PbS films. The "nanocrystalline" film had a very high electrical resistance (10(10)-10(11)Omega/square) compared with the "standard" film (10(5)-10(6)Omega/square). Both types of films proved to be sensitive to the surrounding atmosphere, air or vacuum. Thermally Stimulated Current (TSC) measurement had shown the presence of trap concentration in the both cases, probably due to the large amount of disordered regions.