National Institute Of Materials Physics - Romania

Publications

839 articles found

651. Functional ZnO thin films obtained by radiofrequency beam assisted pulsed laser deposition

Authors: Epurescu, G; Scarisoreanu, ND; Matei, DG; Dinescu, G; Ghica, C; Nistor, LC; Dinescu, M

Published: 2008, ROMANIAN REPORTS IN PHYSICS, 60, +, DOI:

Piezoelectric and p type semiconductor ZnO thin films were deposited by radiofrequency beam assisted pulsed laser deposition. Optical, electrical and structural properties were found to depend on both deposition parameters and radiofrequency beam characteristics.

652. Raman and FTIR studies on electro-reduction of single-walled carbon nanotube films in the presence of Li salts

Authors: Baltog, I; Baibarac, M; Lefrant, S; Mevellec, JY

Published: JUL-OCT 2008, DIAMOND AND RELATED MATERIALS, 17, 1564, DOI: 10.1016/j.diamond.2008.01.041

Electrochemical reduction of single-walled carbon nanotube (SWNT) films in the presence of Li salts dissolved ill acetonitrile (AN), as an anhydrous medium, was investigated by Raman scattering, FTIR spectroscopy and TEM studies. Differences between the in-situ and ex-situ Raman spectra recorded on the SWNT films immersed in the Li salt/AN solution consist in the fort-nation of two reaction products with different stability in air. One corresponds to SWNTs doped with Li+ ions, a compound that is instable in air. The other, stable in air, exhibits in the Raman spectrum recorded at excitation wavelengths of 676 and 1064 nm an enhanced D band, a disappearance of the Breit-Wigner-Fano component and a significant decrease in the radial breaching mode intensity. Besides, in FTIR spectra, one observes: i) a down-shift of the absorption bands from 1456 and 1540 cm(-1) to 1440 and 15 10 cm(-1), respectively accompanied by an increase of their intensities and ii) an up-shift of the IR band from 1170 to 1192 cm(-1). The influence of the applied reduction potential and cycle voltammograms number on the vibrational features of the second product is shown, too. A recovery of the initial vibrational features of SWNTs is achieved by a subsequent treatment with an aqueous HCl 1M solution. (C) 2008 Elsevier B.V. All rights reserved.

653. EIS studies of electrodeposition process of manganese and copper doped ZnO wires

Authors: Sima, M; Enculescu, I; Sima, M; Vasile, E; Visan, T

Published: MAR-APR 2008, SURFACE AND INTERFACE ANALYSIS, 40, 565, DOI: 10.1002/sia.2721

Electrodeposition of manganese- and copper-doped ZnO wires into polycarbonate membranes, from an aqueous solution containing 0.05 mol dm(-3) Zn(NO3)(2)+ 0.01 mol dm(-3) Mn(NO3)(2)+ 0.0005 mol dm(-3) Cu(NO3)(2)+ 0.0075 mol dm(-3) lactic acid, pH = 4.7 was investigated using linear sweep voltammetry and electrochemical impedance spectroscopy (EIS). The equivalent electrical circuits for fitting experimental results were similar to those for characterization of metal/polymer coating systems. impedance data and voltarnmetric curves showed that an increase of local pH due to reduction process of nitrate ions induces the co-precipitations of metal ions in the proximity of electrode as oxides. Copyright (c) 2008 John Wiley & Sons, Ltd.

654. Resistive sensor for water salinity

Authors: Popescu, M; Lorinczi, A; Sava, F; Savu, V; Savastru, D

Published: DEC 2007, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 9, 3956, DOI:

A simple electrical resistance sensor for monitoring of the coastal marine waters has been developed. The good sensitivity and reproducibility of the measurements make this sensor attractive for using in the research of the mixing of sweet (river) waters with the marine water, as well as the variation in the depth of the sea of the water salinity. Another advantage of the sensor is the possibility to monitor the water salinity by simply tracing the electrical resistance when the sensor is drawn at the surface or vertically in the sea and ocean waters.

655. DC conductivity in GeSb2Te4 and (GeSb2Te4)(90)(SnSe2)(10) phase change materials

Authors: Popescu, M; Kubliha, M; Kaluzny, J; Velea, A; Lorinczi, A

Published: DEC 2007, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 9, 3953, DOI:

The dc electrical conductivity of the bulk amorphous GeSb2Te4 material has been investigated. Pure and samples doped by 10 at. % SnSe2 have been measured. The conductivity in the samples has been compared with that of SnSe2 bulk sample. The activation energy of the doped sample is 0.165 eV. During heating the conductivity of doped material increases, reaches a maximum and then decreases. The comparison with the pure SnSe2 samples allows to explain this behavior by the release above 148 degrees C of a small amount of selenium not bonded in the network.

656. Thickness oscillation effect in photoexpansion and photocontraction of amorphous selenium

Authors: Popescu, M; Sava, F; Shimakawa, K; Ikeda, Y; Babin, V

Published: NOV 2007, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 9, 3562, DOI:

Thickness oscillations under light irradiation or by switching-off the light have been revealed in amorphous selenium films. The explanation was given in the frame of a theory that takes into account the balance between the expansion of the inter-chain distance due to electrical charging and better ordering of chains due to freedom of chains to accommodate into the structure as a result of the diminishing or increasing of the spatial hindrance.

657. Interfacial tension of some liquid crystals in the cyanobiphenyl series at the interface with glycerol

Authors: Beica, T; Moldovan, R; Zgura, I; Frunza, S

Published: NOV 2007, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 9, 3627, DOI:

The temperature dependence of the interfacial tension for three compounds from the homologous series of alkylcyanobiphenyl (nCB), 5CB, 7CB and 8CB, at the interface with glycerol was measured in a temperature range from mesomorphic to isotropic phase. The drop shape method of measure was used. The interfacial tension of all the studied liquid crystals presents an anomalous behaviour with maximum and small upward jumps at the phase transitions, in rising temperature.

658. (Te/SnSe2)(3) multilayers deposited by pulsed laser deposition. Structure and gas sensing properties

Authors: Lorinczi, A; Sava, F; Tomescu, A; Simion, C; Socol, G; Mihailescu, IN; Popescu, M

Published: NOV 2007, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 9, 3492, DOI:

Multilayers made of alternative layers of composition SnSe2 and tellurium (three pairs) have been prepared by pulsed laser deposition (PLD). The complex films have been investigated by X-ray diffraction. After a special annealing in oxygen fluence at various temperatures, up to 620 degrees C, the films were investigated both by X-ray diffraction and for gas sensing. Gas sensing properties were tested for water vapours, carbon monoxide (CO) and methane (CH4). After annealing at high temperature, the structure of the multilayer samples show oxide phases like TeO2, SnO2 and a mixed oxide ternary phase SnTe3O8. The annealed multilayers show good sensing properties to water vapours and CO gas.

659. Crystallization of PLD deposited ITO thin films by thermal treating in various gaseous environments

Authors: Viespe, C; Grigoriu, C; Popescua, M; Sava, F; Lorinczi, A; Velea, A; Zamfira, S

Published: NOV 2007, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 9, 3566, DOI:

ITO films of composition (In2O3)(0.9) - (SnO2)(0.1) have been prepared by pulsed laser deposition (PLD).The films were found to be amorphous. The structure and evolution of the films during annealing in air, oxygen atmosphere and reducing atmosphere (CO2) have been investigated by X-ray diffraction. The films annealed in ambient atmosphere start to crystallize under 250 degrees C annealing temperature. The films treated in oxygen atmosphere crystallize at higher temperature (similar to 300 degrees C).

660. Investigation of the properties of indiurn tin oxide-organic contacts for optoelectronic applications

Authors: Stanculescu, A; Stanculescu, F

Published: OCT 15 2007, THIN SOLID FILMS, 515, 8737, DOI: 10.1016/j.tsf.2007.03.120

This paper presents some investigations on the electrical transport properties of ITO/single (double) layer organic semiconductor (m-DNB, benzil, PTCDA, Alq3) contacts in SIS-like (ITO/organic/Si) and MIS-like (ITO/organic/metal) heterostructures. The I-V characteristics have emphasised the injection properties of different contacts and the effect of space charge limited currents in correlation with the type and preparation conditions of the contacts. We have studied the influence of the type of contact (In/ITO; In/Al) on the electrical conduction in Alq3/PTCDA/Si/In heterostructure. In a planar grid contact configuration for In/Al/PTCDA/Al/In structure we have observed the effect of the low electric field on the shape of the I-V characteristic. (c) 2007 Elsevier B.V All rights reserved.