National Institute Of Materials Physics - Romania

Publications

849 articles found

511. Structural and piezoelectric characteristics of BNT-BT0.05 thin films processed by sol-gel technique

Authors: Cernea, M; Trupina, L; Dragoi, C; Vasile, BS; Trusca, R

Published: FEB 25 2012, JOURNAL OF ALLOYS AND COMPOUNDS, 515, 170, DOI: 10.1016/j.jallcom.2011.11.129

Polycrystalline ferroelectric lead-free (Bi0.5Na0.5)(0.95)Ba0.05TiO3 (BNT-NT0.05) thin films have been deposited on Pt/TiO2/SiO2/Si substrates by an optimized sol-gel/spin-coating process. The film thermal treated at 700 degrees C is dense and well crystallized in the rhombohedral perovskite phase. The film is composed of polyhedral shaped primary particles with an average size of approximately 35 nm, and has a smooth surface of 4.52 nm root mean square roughness (RMS). The nanoscale electrical properties of the film were investigated by piezoforce microscopy (PFM). The PFM data showed that most of the grains seem to be constituted of ferroelectric multiple domains. The maximum dielectric constant measured at zero bias voltage is about 210 and the leakage current density has a value of about 3 x 10(-5) A/cm(2) at an applied voltage about 8 V. These results indicate that, the BNT-NT0.05 thin film is a promising functional lead-free ferroelectric material. (C) 2011 Elsevier B. V. All rights reserved.

512. Photoluminescence and Raman evidence for mechanico-chemical interaction of polyaniline-emeraldine base with ZnS in cubic and hexagonal phase

Authors: Scocioreanu, M; Baibarac, M; Baltog, I; Pasuk, I; Velula, T

Published: FEB 2012, JOURNAL OF SOLID STATE CHEMISTRY, 186, 223, DOI: 10.1016/j.jssc.2011.12.012

The mechanico-chemical interaction of a polyaniline-emeraldine base (PANI-EB) with ZnS in the cubic and wurtzite phases is studied by Raman spectroscopy and photoluminescence (PL). The results demonstrate that such an interaction leads to the formation of a PANI-salt and metallic Zn. Regardless of the structural form of the ZnS, the formation PANI-salt is indicated by a band in the Raman spectrum that shifts from 1162 to 1176 cm(-1) and the appearance of a new band at 1330 cm(-1) that indicates the protonated structure of a PANI-salt. The presence of the second product is determined by comparative PL studies performed on ZnS that has interacted mechanico-chemically with PANI-EB and metallic Zn powder. The variations of the PL spectra and their associated excitation spectra are explained as resulting from the charge collection processes that occur in the composite materials produced by the mechanico-chemical interaction between ZnS and PANI-EB or metallic Zn. (C) 2011 Elsevier Inc. All rights reserved.

513. Interface characterization and atomic intermixing processes in Be/W bilayers deposited on Si(001) substrates with Fe buffer layers

Authors: Kuncser, V; Palade, P; Schinteie, G; Sandu, SG; Trupina, L; Lungu, GA; Gheorghe, NG; Teodorescu, CM; Porosnicu, C; Jepu, I; Lungu, CP; Filoti, G

Published: JAN 25 2012, JOURNAL OF ALLOYS AND COMPOUNDS, 512, DOI: 10.1016/j.jallcom.2011.09.063

Structural aspects and atomic intermixing processes in Be/W bilayers deposited on Si(0 0 1) substrates with Fe buffer layers enriched in the (57)Fe Mossbauer isotope have been studied via atomic force microscopy, grazing incidence X-ray diffractometry, X-ray reflectometry, X-ray photoelectron spectroscopy and conversion electron Mossbauer spectroscopy. The mentioned investigations allowed a full sequential characterization of the involved interfaces. Various ionic configurations appeared for Fe or W, while an amorphous state was observed in the case of Be. It has been proven that the Be layer has a negative influence on the roughness of the whole structure, which however presents an oxidation gradient from more oxidized elements at the surface towards more reduced elements in deeper layers. A strong diffusion of the W atoms inside the Be layer, induced by the deposition method, as well as of the Fe atoms inside the Be layer, induced by thermal annealing, has been evidenced. (C) 2011 Elsevier B.V. All rights reserved.

514. OBTAINING AND CHARACTERIZATION OF HA/Y2O3:alpha Al2O3 SYSTEM FOR BIOAPPLICATIONS

Authors: Mercioniu, I; Stan, GE; Bercia, R; Ciuca, S; Popescu-Pogrion, N

Published: JUL-SEP 2012, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 7, 932, DOI:

A new HA/Y2O3:alpha Al2O3 system was obtained by the deposition of a hydroxyapatite thin layer (similar to 150 nm), by magnetron sputtering, onto sintered substrates of low yttria (150 ppm) doped alumina. The yttria doped alumina was synthesized from very pure nanopowders, by mechanical homogenization, followed of pressing, sintering and different annealing regimes, in order to obtain bodies with various degree of nano-micro-structuration. TEM/HRTEM, SEM and EDS morpho-compositional analysis techniques were used to characterize the yttria doped alumina substrate and the hydroxyapatite superficial layer. The interfacial bonding strength between the sintered substrate and the hydroxyapatite thin film was analyzed by SEM. The evolution of the grains growth of the Y2O3:alpha Al2O3 substrate samples, with and without the hydroxyapatite covering layer is observed and discussed. A strong structural interdependence between the covering layer and the sintered substrate was emphasized. The grains' growth behaviour of the studied samples showed a linear evolution. A mathematical model for the grain growth process description was built, the grain size being interpreted as a random variable having a log-normal or Weibull probability density function.

515. TILT c AXIS CRYSTALLITE GROWTH OF ALUMINIUM NITRIDE FILMS BY REACTIVE RF-MAGNETRON SPUTTERING

Authors: Stan, GE; Pasuk, I; Trinca, LM; Galca, AC; Enculescu, M; Miculescu, F

Published: JAN-MAR 2012, DIGEST JOURNAL OF NANOMATERIALS AND BIOSTRUCTURES, 7, 50, DOI:

The article reports on the tilted growth of textured aluminium nitride thin films obtained by radio-frequency magnetron sputtering onto 50 mm diameter Si (111) wafers, in reactive atmosphere, in a planar sputtering system without tilting the substrate and with no additional sputtering geometry alterations. The films were investigated using, X-ray diffraction, spectroscopic ellipsometry and scanning electronic microscopy, done by local measurements on the wafer surface, at different distances from the centre. A progressive increase of the tilt angle when moving away from the sample centre has been found. The maximum tilt angle of the columnar AlN crystallites, obtained near the edges of the wafer, is about 7 degrees. The results showed also that tilting is associated with smaller thickness and larger dispersion of the c axis orientation. Synthesizing inclined c axis AlN films should allow the fabrication of surface acoustic wave devices based on shear waves for liquid sensor applications.

516. A HIGH PERFORMANCE PIEZOCERAMIC MATERIAL FOR A VIBRATION TRANSDUCER FOR BALANCING OF ROTATING PARTS

Authors: Miclea, CT; Cioangher, M; Miclea, CF; Trupina, L; Miclea, C; Amarande, L; Spanulescu, S; Faibis, R

Published: 2012, 2012 INTERNATIONAL SEMICONDUCTOR CONFERENCE (CAS), VOLS 1 AND 2, 2, 294, DOI:

A high performance piezoceramic material of PZT type, doped with 6 atomic % W, was prepared in order to be used as sensing element for a vibration transducer used to equilibrate the motor-fan group of auto vehicles. The piezoelectric parameters of material showed high values which recommended it for the vibration transducer. The transducer consists of a ring shaped active element sandwiched between two steel blocks. The transducer works in quasistatic regime, at frequencies much lower than the resonance frequency, being tightly screwed in the measurement system by a metallic cover attached at the back end.

517. Pizeoelectric epitaxial sol-gel Pb(Zr0.52Ti0.48)O-3 film on Si(001)

Authors: Yin, S; Le Rhun, G; Defay, E; Vilquin, B; Niu, G; Robach, Y; Dragoi, C; Trupina, L; Pintilie, L

Published: 2012, 2012 INTERNATIONAL SYMPOSIUM ON APPLICATIONS OF FERROELECTRICS HELD JOINTLY WITH 11TH IEEE ECAPD AND IEEE PFM (ISAF/ECAPD/PFM), DOI:

Epitaxial Pb(Zr0.52Ti0.48)O-3 (PZT) thin film has been successfully integrated on Si(001) substrate by sol-gel method. SrTiO3 (STO) layer deposited on Si by Molecular Beam Epitaxy (MBE) acts as a template layer in this study to avoid the formation of amorphous SiO2, and allows the chemical compatibility for further epitaxial growth. For bottom electrode, SrRuO3 (SRO) layer grown by Pulsed Laser Deposition (PLD) on STO/Si was used. Epitaxial single crystalline growth of PZT film after Rapid Thermal Annealing (RTA) at 650 C was evidenced by X-Ray Diffraction (XRD). The following relationship in the heterostructure was deduced: [110] PZT (001) // [110] SRO (001) // [110] STO (001) // [100] Si (001). A clear piezoelectric response of the film was observed by Piezoresponse Force Microscope (PFM). Moreover, the structural STO quality was proved to have a major impact on the electrical properties of PZT films.

518. ZnO Thin Films Deposited on Textile Material Substrates for Biomedical Applications ZnO Thin Films Deposited on Textiles

Authors: Duta, L; Popescu, AC; Dorcioman, G; Mihailescu, IN; Stan, GE; Zgura, I; Enculescu, I; Dumitrescu, I

Published: 2012, TECHNOLOGICAL INNOVATIONS IN SENSING AND DETECTION OF CHEMICAL, BIOLOGICAL, RADIOLOGICAL, NUCLEAR THREATS AND ECOLOGICAL TERRORISM, 210, DOI: 10.1007/978-94-007-2488-4_20

We report on the coating with ZnO adherent thin films of cotton woven fabrics by Pulsed laser deposition technique in order to obtain innovative textile materials, presenting protective effects against UV radiations and antifungal action.

519. Ba(Zn1/3Ta2/3)O-3 perovskite ceramics doped with Nb5+, Ce4+ or Yb3+

Authors: Busuioc, C; Jinga, SI; Stoleriu, S; Nedelcu, L; Andronescu, E

Published: MAR-APR 2012, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 14, 244, DOI:

Ba(Zn1/3Ta2/3)O-3 (BZT) perovskite material has stimulated a large interest due to its excellent dielectric properties in microwave frequency range, enabling the miniaturization of communications devices. In this work, BZT ceramics were prepared by the conventional solid-state reaction method, being doped with Nb5+, Ce4+ or Yb3+. BZT resonators were compositional, structural, morphological and electrical characterized. The influence of the dopants and sintering temperature on the microwave dielectric properties of BZT samples was investigated. The resonator doped with 0.5 mol% Nb2O5 and sintered at 1600 degrees C / 2 h exhibits the best dielectric behaviour: e(r) similar to 25.9 and Qxf similar to 159 THz.

520. Ba(X1/3Ta2/3)O-3 COMPLEX PEROVSKITES FOR MICROWAVE AND MILLIMETER-WAVE APPLICATIONS

Authors: Nedelcu, L; Busuioc, C; Banciu, MG; Ramer, R

Published: 2012, 2012 INTERNATIONAL SEMICONDUCTOR CONFERENCE (CAS), VOLS 1 AND 2, 2, 306, DOI:

Ba(X1/3Ta2/3)O-3 (X = Zn, Mg) perovskites were prepared by using the solid state reaction method. X-ray diffraction and scanning electron microscopy were employed for structural and morphological characterization of Ba(X1/3Ta2/3)O-3 samples. The dielectric constant of the resonators was 28 for Ba(Zn1/3Ta2/3)O-3 and 24 for Ba(Mg1/3Ta2/3)O-3. A strong influence of the cation ordering on the dielectric loss has been found. The achieved values of Q x f product, ranging from 100 to 200 THz, make Ba(X1/3Ta2/3)O-3 dielectric resonators attractive for microwave and millimetre-wave applications.