National Institute Of Materials Physics - Romania

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5781 articles found

3031. SEQUENTIAL DEPOSITION OF MULTISEGMENT NANOWIRES

Authors: Matei, E; Preda, N; Enculescu, M; Ansermet, JP; Molares, MET; Enculescu, I

Published: OCT-DEC 2010, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 5, 1076, DOI:

Electrochemical replication of nanoporous membranes represents a facile approach towards the fabrication of nanostructures with tailored properties. By the template method we prepared multisegment nanowires with tailored structure. The first step of the process was the fabrication of the nanoporous template by swift heavy ion irradiation and subsequent selective etching of the ion track. The next step was to fill the pores with the desired combination of materials. In this manner, by sequential electrodeposition steps of metal and semiconductor we prepared Ni - CdTe and Ni - ZnO - Ni nanowires.

3032. PREPARATION AND PROPERTIES OF BARIUM STEARATE MULTILAYERS WITH CARBON NANOTUBES, MANGANESE PORPHYRIN AND SILVER NITRATE

Authors: Simandan, ID; Popescu, M; Lorinczi, A; Velea, A; Fagadar-Cosma, E

Published: OCT-DEC 2010, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 5, 1033, DOI:

Barium stearate multilayer samples have been deposited by the Langmuir-Blodgett technique. Carbon nanotubes have been added in the deposition solution. The structural properties have been studied. The effect of the doped multilayers has been tested against the solution of ammonium nitrate in water. The effect of (5,10,15,20-tetraphenyl)-porphinato manganese (III) chloride, (MnTPP)Cl, on the multilayer sample has been tested. The change of resistivity of the multilayer samples modified by manganese porphyrin, as a function of the ultraviolet radiation has been discovered and investigated. The increase of the resistance during irradiation is a reversible process, although a slow one. This effect could give a basis for applications in UV sensors and switches. Finally, a photo-resistive effect (induced by UV light) has been discovered in Barium stearate layers doped by silver nitrate.

3033. Effects of layer by layer deposition on the structural and optical characteristics of thin films

Authors: Prepelita, P; Medianu, R; Garoi, F; Moldovan, A; Vlaicu, AM

Published: 2010, ROMOPTO 2009: NINTH CONFERENCE ON OPTICS: MICRO- TO NANOPHOTONICS II, 7469, DOI: 10.1117/12.859695

CuIn1-xGaxS2 (CIGS2) thin-films for solar cells were prepared by rf-magnetron sputtering and were deposited on glass substrate. These films were prepared using a stepwise process consisting of succesive deposition of CuInGa (d = 1500 nm) and ZnS (d = 200 nm) layers. Each layer was structurally characterized by X-ray diffraction and atomic force microscopy. The microstructural and optical properties of CIGS2 component films of the solar cell in comparison with those of ZnS and CuInGa films separately deposited onto glass substrates under the same conditions, were studied. Transmission spectra of our thin films are strongly influenced by deposition conditions and nature of the support material and they were recorded for each component film and CIGS2 solar cell.

3034. Magnetization relaxation in YBCO films with improved supercurrent transport properties

Authors: Miu, L; Ivan, I; Badica, P; Jakob, G; Miu, D; Mele, P; Matsumoto, K

Published: 2010, 9TH EUROPEAN CONFERENCE ON APPLIED SUPERCONDUCTIVITY (EUCAS 09), 234, DOI: 10.1088/1742-6596/234/1/012026

The relaxation of the irreversible magnetization in optimally doped YBCO films with natural and artificial pinning centres was measured in zero-field cooling conditions using SQUID magnetometry. The external magnetic field H was oriented along the c axis. An appropriate method for the determination of the characteristic vortex pinning energy from the normalized vortex-creep activation energy is discussed. This is based on the existence of a crossover elastic (collective) vortex creep at low temperatures T - plastic vortex creep at high T, caused by the T dependent macroscopic currents induced in the sample during magnetization measurements.

3035. PRELIMINARY BIOCOMPATIBILITY STUDIES OF HYDROXYAPATITE COATED IRON OXIDE

Authors: Andronescu, E; Ciobanu, CS; Pall, L; Costache, M; Predoi, D

Published: 2010, REVISTA ROMANA DE MATERIALE-ROMANIAN JOURNAL OF MATERIALS, 40, 249, DOI:

Bioceramic composites were obtained by combining two biocompatible components (by example- in our studies - hydroxyapatite and iron oxide nanoparticles). The preparation method determines the particle size and shape, the size distribution, the surface chemistry of the iron oxide particles and consequently their magnetic properties. The samples were analysed by X-ray diffraction and IR spectroscopy. Their thermal behaviour was studied by thermogravimetric and thermodifferential analysis. These characterization techniques confirmed the presence of hydroxyapatite on the magnetite surface. Osteoblast cell cultures were used to determine cell proliferation, viability and cytotoxicity on interaction with the samples. The cultures displayed good in vitro behaviour.

3036. Nanostructured thin layers of vanadium oxides doped with cobalt, prepared by pulsed laser ablation: chemistry, local atomic structure, morphology and magnetism

Authors: Teodorescu, CM; Socol, G; Negrila, C; Luca, D; Macovei, D

Published: 2010, JOURNAL OF EXPERIMENTAL NANOSCIENCE, 5, 526, DOI: 10.1080/17458081003671675

Cobalt-doped vanadium oxide thin layers prepared by pulsed laser ablation are investigated from the following points of view: (1) the chemical states by X-ray photoelectron spectroscopy (XPS), (2) the local atomic order by X-ray absorption fine structure at both vanadium and cobalt K-edges, (3) the morphology of the films by atomic force microscopy (AFM) and (4) the magnetic properties by magneto-optical Kerr effect (MOKE). The chemical composition of the host matrix was found to be close to VO2 at the sample surface, with V2O3 in the bulk. Co ions are found near the surface in high ionisation states Co4+ (for the samples synthesised in a high vacuum condition, denoted by VO1), or with Co(4-)+ (for the samples synthesised in an oxygen atmosphere, denoted by VO2), whereas in the bulk, Co1.5+ is obtained for VO1 and Co2+ is obtained for VO2. The AFM revealed nanoparticles with sizes 10-25 nm for VO1 samples, whereas a few bigger nanoparticles are observed for VO2 samples. The VO1 samples presented high coercitive fields with a relatively low saturation magnetisation at room temperature, superposed with a superparamagnetic component attributed to the observed nanoparticles, whereas the VO2 samples presented double-loop hysteresis curves, indicating the co-existence of two kinds of magnetic moieties with antiparallel coupling at zero applied field. The proposed two magnetic phases are Co-doped V2O3 and VO2.

3037. DIFFERENCES IN THE GAS SENSING PROPERTIES READOUT WITH N AND P-TYPE MOX MATERIALS

Authors: Simion, CE; Tomescu-Stanoiu, A

Published: 2010, 2010 INTERNATIONAL SEMICONDUCTOR CONFERENCE (CAS), VOLS 1 AND 2, 204, DOI:

The way in which surface changes are transduced into a variation of an electrical parameter (often electrical resistance) depends on the surface oxidation level, material morphology its semiconductor behaviour, etc. Therefore, if one wants to understand more about the way in which gas-surface interactions affect the gas sensing properties of material, complex phenomenological and spectroscopic investigations are needed. Herein, by simultaneous DC and relative work function investigations we could explain the differences induced by the MOX semiconductor character (n and p-type) to the surface phenomena transduction mechanism.

3038. NON-LINEAR RAMAN SCATTERING EFFECTS GENERATED BY THE SURFACE PLASMONS EXCITATION

Authors: Baltog, I; Baibarac, M; Mihut, L; Smaranda, I

Published: 2010, ROMANIAN REPORTS IN PHYSICS, 62, 593, DOI:

An inciting and much debated subject in the surface enhanced Raman (SERS) studies is an unusual anti-Stokes Raman spectrum distinguished by an abnormal intensity, increasing with the vibrational wavenumber and some discrepancies with regard to the Stokes spectrum. We demonstrate that the abnormal anti-Stokes Raman emission on single walled carbon nanotubes and poly(3,4-ethylenedioxy thiophene) synthtetized electrochemically appears as a consequence of two corroborating effects: resonance, which occurs when the energy of the excitation light is near or coincident with the energy of an electronically allowed transition, and the SERS effect achieved by the excitation of surface plasmons. An abnormal intense Raman emission in the Stokes branch, reminiscent to a stimulated Raman effect, which increases exponentially with the intensity of exciting light is reported for the first time in the case of SWNTs.

3039. Increased Bioactivity of Cranio-Spinal Implants Functionalized with Hydroxyapatite Nanostructured Coatings: Morpho-Structural Characterization and In-Vitro Evaluation

Authors: Duta, L; Socol, G; Sima, F; Mihailescu, IN; Stan, GE; Marcov, DA; Sima, LE; Petrescu, SM; Melinescu, A; Ianculescu, A; Chiriac, A; Poeata, I

Published: 2010, 2010 ADVANCED TECHNOLOGIES FOR ENHANCING QUALITY OF LIFE (AT-EQUAL), 130, DOI: 10.1109/ATEQUAL.2010.27

We report on the versatility of pulsed laser deposition and radio frequency magnetron sputtering deposition methods to synthesize highly adherent bioactive hydroxyapatite thin layers on cranio-spinal implants as appropriate biofixation alternatives.

3040. IMPROVING THE CUBIC ZnS NANOCRYSTALS QUALITY BY SELF-ASSEMBLING INTO A MESOPOROUS STRUCTURE

Authors: Nistor, SV; Nistor, LC; Stefan, M; Ghica, D; Mateescu, CD; Birjega, R

Published: 2010, ROMANIAN REPORTS IN PHYSICS, 62, 328, DOI:

Nanocrystals of cubic ZnS (cZnS) doped with 02 % mol Mn2+, self-assembled into a mesoporous structure, have been prepared at room temperature by a surfactant-assisted liquid-liquid reaction The X-ray diffraction measurements confirm the formation of a sponge-like mesoporous structure built from ZnS nanocrystals with cubic (sphalerite) structure and pores of similar diameter of (1 8 +/- 0 2) nm. The Transmission Electron Microscopy (TEM) images show that the mesoporous structure consists of nanocrystals of cZnS with a tight size distribution centered around the average diameter value (21 +/- 0 3) nm The analysis of the observed Election Paramagnetic Resonance (EPR) spectrum demonstrates the presence of the Mn2+ activating ions at isolated sites in the mesoporous material, resulting in three types of paramagnetic centers called Mn2+(I), Mn2+(II) and Mn2+(III) The EPR spectrum of the Mn2+(I) center, attributed to substitutional Mn2+ ions at Zn2+ cation sites in the ZnS nanocrystals, exhibits the smallest linewidth values reported so far, reflecting an increased lattice ordering The high quality of the nanocrystals forming the mesoporous cZnS Mn, as reflected in a tight nanocrystallites size distribution and reduced crystallites lattice disorder, is attributed to the restraining effect of the self-assembling