National Institute Of Materials Physics - Romania

Publications

860 articles found

831. Electrical and structural properties of anodized porous silicon

Authors: Ciurea, ML; Pentia, E; Lazar, M; BeluMarian, A; Zavaliche, F; Manaila, R

Published: 1996, CAS '96 PROCEEDINGS - 1996 INTERNATIONAL SEMICONDUCTOR CONFERENCE, 19TH EDITION, VOLS 1 AND 2, 236, DOI:

832. Symmetric SQW structure with low confinement factor for high power laser diodes

Authors: Buda, M; Iordache, G; Vlaicu, M; Cengher, D; Diaconescu, D

Published: 1996, CAS '96 PROCEEDINGS - 1996 INTERNATIONAL SEMICONDUCTOR CONFERENCE, 19TH EDITION, VOLS 1 AND 2, 210, DOI:

833. INTERFACE TRAPPING STATES IN MISIM STRUCTURES, WITH ZNS-MN

Authors: PETRE, D; PINTILIE, I; CIUREA, ML; BOTILA, T

Published: MAY 1 1995, THIN SOLID FILMS, 260, 57, DOI: 10.1016/0040-6090(94)06467-9

Optical charging spectroscopy and thermally stimulated depolarization measurements were performed on metal-insulator-semiconductor-insulator-metal structures with a ZnS:Mn active layer. Two groups of trapping centres situated at every insulator-semiconductor interface were in evidence. Their depths were found to be centred at 0.55 eV and 0.875 eV respectively in the forbidden gap of a ZnS:Mn film. A partial thermal healing of these interface states was observed.

834. Modified ruthenium exchanged zeolites for enantioselective hydrogenation

Authors: Parvulescu, VI; Parvulescu, V; Coman, S; Radu, C; Macovei, D; Angelescu, E; Russu, R

Published: 1995, PREPARATION OF CATALYSTS VI: SCIENTIFIC BASES FOR THE PREPARATION OF HETEROGENEOUS CATALYSTS, 91, 570, DOI:

Preparation of modified ruthenium molecular sieves has been investigated in two steps deposition of ruthenium and modifying of ruthenium molecular sieves in presence of ligands. As support sieve there were used two molecular sieves with large pore apertures and low acidity strength (zeolite L and APO-34). Correlation of in situ W-VIS ruthenium deposition measurements with catalyst characterisation revealed that ruthenium deposition takes place not only through ionic exchange but also through adsorption of ruthenium hydrolysed species. Modifying of the ruthenium molecular sieves catalysts with ligands has as effect a diminution of electronic charge on metal. The experimental data indicate that the presence of ligand favours an enantioselective hydrogenation of D-fructose to D-mannitol even if the yields are not very high.

835. EFFECTS OF ANNEALING ON THE CONDUCTIVITY OF C-60 THIN-FILMS

Authors: BELUMARIAN, A; MANAILA, R; STOICA, T; DRAGOMIR, A; MANCIU, M; DEVENYI, A; BRAUN, T

Published: 1995, FULLERENE SCIENCE AND TECHNOLOGY, 3, 509, DOI: 10.1080/153638X9508543803

Films of C-60, at different stages of annealing of T-c = 200 degrees and 300 degrees C have been electrical characterized over the temperature domain from -130 degrees C to T-c. X-ray diffraction revealed a random polycrystalline fee structure with stacking defects of an intrinsic nature, due to deposition conditions. The value of room-temperature conductivity was found to be in the range (6.3-1.0)*10(-10) (Omega cm)(-1). In the stable annealed state the conductivity showed an activated temperature dependence above 423 K and a non-activated dependence below 330-280 K. The activation energies E(2) 0.8 eV (film thickness 0.70 mu m) and E(2) = 1.0 eV (film thickness 2.40 mu m) were in good agreement with the energy gap values (1.63 eV and 2.08 eV) which were deduced from the al;sorption spectral dependence. Annealing decreased the non-activated contribution to conduction, extending the intrinsic conduction temperature range.

836. HIGH POWER OPERATION OF LOW CONFINEMENT LASER DIODE STRUCTURE

Authors: PETRESCUPRAHOVA, IB; BUDA, M; IORDACHE, G; KAROUTA, F; SMALBRUGGE, E; VANDEROER, TG; KAUFMANN, LMF; WOLTER, JH; VANDERVLEUTEN, WG

Published: 1995, FOURTH CONFERENCE IN OPTICS, ROMOPTO '94, 2461, 9, DOI: 10.1117/12.203458

837. CONFINEMENT FACTOR MEASUREMENT IN LASER DIODES BY ABSORPTION LOSS MODULATION WITH INJECTED CARRIERS

Authors: CENGHER, CD; VLAICU, AM; IORDACHE, G; PETRESCUPRAHOVA, IB

Published: 1995, FOURTH CONFERENCE IN OPTICS, ROMOPTO '94, 2461, 64, DOI: 10.1117/12.203503

838. MAGNETOTRANSPORT AND PHOTOLUMINESCENCE OF 2-DIMENSIONAL HOLE GASES IN SI/SI1-XGEX/SI HETEROSTRUCTURES

Authors: LOO, R; VESCAN, L; HARTMANN, A; APETZ, R; ZASTROW, U; SCHAPERS, T; LEUTHER, A; DIEKER, C; LUTH, H; GARTNER, P; STOICA, T

Published: DEC 15 1994, PHYSICAL REVIEW B, 50, 18123, DOI: 10.1103/PhysRevB.50.18113

839. TRAPPING LEVELS IN BI12SIO20 CRYSTALS

Authors: PETRE, D; PINTILIE, I; BOTILA, T; CIUREA, ML

Published: AUG 15 1994, JOURNAL OF APPLIED PHYSICS, 76, 2219, DOI: 10.1063/1.357637

Localized levels play a major role in the electro-optic properties of Bi12SiO2O (BSO) crystals. The activation energy of trapping levels was studied by different laboratories using various methods (e.g., thermally stimulated currents and photoinduced current transient spectroscopy). A more sensitive investigation of traps in undoped BSO single crystals has been performed by optical charging spectroscopy. The presence of traps in the energy range 0.2-1.1 eV was found, and the results are in good agreement with previous studies. On the other hand, this method led us to suggest that the trapping levels observed can be both electron traps and hole traps. For deep trapping levels at higher temperatures, a strong temperature dependence of the cross section was observed.

840. HIGH GAP SPUTTERED DLC LAYERS

Authors: MOROSANU, CO; STOICA, T; DEMARTINO, C; DEMICHELIS, F; TAGLIAFERRO, A

Published: APR 1994, DIAMOND AND RELATED MATERIALS, 3, 816, DOI: 10.1016/0925-9635(94)90275-5

Adherent and transparent unhydrogenated DLC layers were deposited by means of r.f. and d.c. magnetron sputtering at low deposition temperatures. The optical gap value increases from 0.7 to 2.2 eV when deposition pressure is increased from 10(-2) to 10(-1) Torr. In high gap materials, large amounts of sp3 hybridized carbon atoms are present. When Al contacts are evaporated in coplanar configuration on these high gap materials, rectifying and photoelectrical effects are observed.