National Institute Of Materials Physics - Romania

Publications

873 articles found

641. The influence of the top-contact metal on the ferroelectric properties of epitaxial ferroelectric Pb(Zr0.2Ti0.8)O-3 thin films

Authors: Pintilie, L; Vrejoiu, I; Hesse, D; Alexe, M

Published: DEC 1 2008, JOURNAL OF APPLIED PHYSICS, 104, DOI: 10.1063/1.3021293

Electrical properties, i.e., dielectric hysteresis and leakage current, of epitaxial Pb(Zr0.2Ti0.8)O-3 films with bottom SrRuO3 electrode and different metals as top contact were investigated. The leakage current is largely insensitive to the work function of the top metal but increases with decreasing electronegativity as well as with decreasing number of electrons on the d-shell of the top metal. The best rectifying properties are obtained for metals with complete d-shell (Cu, Au, Ag, Pd), while the metals with few electrons on the d-shell (Ta, Cr) form Ohmic-like contacts. (c) 2008 American Institute of Physics. [DOI: 10.1063/1.3021293]

642. An Optimized Method for Electroless Pd Deposition onto Alumina Substrates

Authors: Petica, A; Anicai, L; Pasuk, I

Published: DEC 2008, REVISTA DE CHIMIE, 59, 1381, DOI:

An optimized electroless deposition procedure to form Pd membranes onto ceramic substrates involving the thermal decomposition of a Pd complex compound ([Pd (NH3)(4)] [PdCl4]) is discussed. This allowed a reaction efficiency of about 90-95%. The proposed method significantly diminishes the Pd wastes as compared with the classical procedure involving hydrazine based reduction step. A Pd layer of about 3-5 mu m has been uniformly deposited on the inner surface of the alpha-Al2O3 based substrate, being characterized by a very good adherence and light grey metallic appearance. Homogeneous films of Pd were obtained by annealing the deposited Pd layers at temperatures higher than 500 degrees C in a hydrogen atmosphere. XRD and laser confocal microscopy techniques have been proved to be suitable to characterize the composition, thickness and uniformity of the formed Pd membranes.

643. Field induced phase segregation in ferrofluids

Authors: Kooij, ES; Galca, AC; Poelsema, B

Published: NOV 1 2008, JOURNAL OF COLLOID AND INTERFACE SCIENCE, 327, 265, DOI: 10.1016/j.jcis.2008.08.029

We study the phase segregation in magnetite ferrofluids under the influence of an external magnetic field. A phase with lower nanoparticle density and corresponding higher optical transmission is formed in the bottom of a glass cell in the presence of only a very modest magnetic field gradient (smaller than 25 T/m). The flux density in our magnetic configuration is simulated using finite element methods. Upon switching off the external magnetic field, the low-density phase develops into a 'bubble'-like feature. The kinetics of this 'bubble' in the absence and presence of a magnetic field are described and analyzed in terms of a simple model, which takes into account buoyancy and drag forces. (C) 2008 Elsevier Inc. All rights reserved.

644. Antiferroelectric-like behavior in polycrystalline Pb(Zr0.2Ti0.8)O-3-BiFeO3 multilayers prepared by sol-gel method

Authors: Pintilie, L; Stancu, V; Dragoi, C; Vlaicu, M

Published: NOV 2008, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 10, 3149, DOI:

Pb(Zr0.2Ti0.8)O-3-BiFeO3 (PZT-BFO) multilayer structures were realized by sol-gel on Pt/Si substrate and their electrical properties were investigated using top Pt, Au and Cu electrodes. All multilayers start and end with PZT films. The polarization-voltage and current-voltage hysteresis loops resemble to those encountered in case of antiferroelectric (AFE) films, although component materials are both ferroelectric (FE). The AFE-like behavior is more clearly visible in the case of three-layer structures of PZT-BFO-PZT type, and it is not dependent of the metal used as top electrode. After fatigue cycling the polarization hysteresis apparently changes from characteristic AFE double-loop to FE single loop, although the four switching current peaks characteristic for an AFE behavior are still present in the current hysteresis. These results suggest the presence of an AFE interfacial coupling between the PZT and BFO layers.

645. SBN thin films growth by RF plasma beam assisted pulsed laser deposition

Authors: Scarisoreanu, ND; Dinescu, G; Birjega, R; Dinescu, M; Pantelica, D; Velisa, G; Scintee, N; Galca, AC

Published: NOV 2008, APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING, 93, 800, DOI: 10.1007/s00339-008-4753-2

SBN thin films were grown on MgO and Silicon substrates by PLD and RF-PLD (radiofrequency assisted PLD) starting from single crystal Sr0.6Ba0.4Nb2O6 and ceramic Sr0.5Ba0.5Nb2O6 stoichiometric targets. Morphological and structural analyses were performed on the SBN layers by AFM and XRD and optical properties were measured by spectroellipsometry. The films composition was determined by Rutherford Backscattering Spectrometry. The best set of experimental conditions for obtaining crystalline, c-axis preferential texture and with dominant 31 degrees in-plane orientation relative to the MgO (100) axis is identified.

646. Nanostructured PZT type thin films prepared by thermonic vacuum arc method

Authors: Rasleanu, D; Ionescu, V; Prodan, G; Ciupina, V; Lungu, CP; Surdu-Bob, C; Osiac, M; Pompilian, O; Badulescu, M; Lungu. AM; Ticos, C; Zaroschi, V; Trupina, L; Miclea, C

Published: NOV 2008, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 10, 3047, DOI:

PZT type films were prepared using the thermionic vacuum arc (TVA) method; a crucible filled PZT type powder (PbO/ZrO/TiO) was heated by a thermo-electron beam emitted by the circular cathode of the TVA gun. Applying high voltage potential (3000 +/- 200V) on the anode from a regulated HEINZINGER high voltage power supply the thermo-electrons were accelerated toward the anode crucible, evaporating the anode materials and initiating a plasma discharge. The morphology and the structure of the prepared films analyzed by transmission electron microscopy, (TEM), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy, showed nanostructured, smooth thin films with specific PZT stoichiometry.

647. PLD and RF-PLD synthesis of Ba0.6Sr0.4TiO3 ferroelectric thin films for electrically controlled devices

Authors: Nedelcu, L; Ioachim, A; Toacsan, MI; Banciu, MG; Pasuk, I; Buda, M; Scarisoreanu, N; Ion, V; Dinescu, M

Published: NOV 2008, APPLIED PHYSICS A-MATERIALS SCIENCE & PROCESSING, 93, 679, DOI: 10.1007/s00339-008-4694-9

Ba0.6Sr0.4TiO3 (BST) bulk ceramic synthesized by solid state reaction was used as target for thin films grown by pulsed laser deposition (PLD) and radiofrequency beam assisted PLD (RF-PLD). The X-ray diffraction patterns indicate that the films exhibit a polycrystalline cubic structure with a distorted unit cell. Scanning Electron Microscopy investigations showed a columnar microstructure with size of spherical grains up to 150 nm. The capacitance-voltage (C-V) characteristics of the BST films were performed by applying a DC voltage up to 5 V. A value of 280 for dielectric constant and 12.5% electrical tunability of the BST capacitor have been measured at room temperature.

648. InN thin films deposited on flexible substrates by reactive RF-magnetron sputtering

Authors: Zoita, NC; Besleaga, C; Braic, L; Mitran, T; Grigorescu, C; Nedelcu, L

Published: NOV 2008, OPTOELECTRONICS AND ADVANCED MATERIALS-RAPID COMMUNICATIONS, 2, 720, DOI:

Indium nitride is an attractive semiconductor material for optoelectronic applications, high-speed electronics and solar cells. We report successful deposition of polycrystalline InN thin films onto kapton polyimide flexible substrates by reactive RF magnetron sputtering method. The optical, structural and morphological characterization data are presented.

649. Studies on multifunctional textile materials. Plasma deposition onto textile materials and onto reference plates

Authors: Beica, T; Nistor, LC; Morosanu, C; Frunza, L; Stan, GE; Zgura, I; Marcov, D; Dorogan, A; Carpus, E

Published: OCT 2008, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 10, 2817, DOI:

The magnetron sputtering method was used to obtain layers of indium tin oxide or hydroxyapatite on glass fiber woven and on reference glass plates. The layers were characterized by scanning microscopy, UV-vis spectroscopy and conductivity measurements. Hydrophilic properties of the woven samples were investigated by optical microscopy following the behavior of a water droplet upon the each of the samples. The change of the drop profile in time due to wetting of the fabric leads to the wetting kinetics. The most efficient treatments to improve the hydrophilic/wetting properties of the glass fiber woven were found.

650. ERRORS IN EVALUATION OF THE KINETIC PARAMETERS IN TEMPERATURE PROGRAMMED REDUCTION

Authors: Munteanu, G; Miclea, C; Segal, E

Published: OCT 2008, JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY, 94, 321, DOI: 10.1007/s10973-008-8998-y

The possibility to determine the kinetic parameters for temperature programmed reduction of Cu/Fe3O4 using only one TPR profile is analyzed. The same data are analyzed both by Friedman's iso-conversional method and another one previously derived and published by the authors. One shows that taking into account the experimental restrictions of Monti and Baiker, the Friedman's method, although gives values of the activation energy smaller than the real values, indicates a very similar dependence of these on the reduction degree. On the basis of some synthetic data one shows that the errors are very large when these recommendations are neglected, being possible to determine a false dependence on the degree of reduction.