National Institute Of Materials Physics - Romania

Publications

5714 articles found

2781. A facile semi-open method for synthesis of non-centrosymmetric superconducting Li-2(Pd,Pt)(3)B bulks and thin films

Authors: Badica, P; Jakob, G

Published: DEC 2010, PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS, 470, S657, DOI: 10.1016/j.physc.2009.11.067

Non-centrosymmetric superconductor Li-2(Pc1-xPtx)(3)B, x = 0-1 was synthesized from mixtures of the elements. A simple semi-open method is proposed using endings-pressed stainless steel tubes placed in a high-vacuum furnace. Heating regime employed a short-time overheating at 900 degrees C and a slow cooling step between T-s and 550 degrees C within 3 h. To adequately compensate Li-losses and attain maximum critical temperature, the optimum T-s and starting Li-content were found to change from 720 to 740 degrees C and from Li-2.4 to Li-2.6, respectively, when x was changing from 0 to 1. It was shown that placing Li separately in the tube also produces superconducting samples. Li being supplied to the (Pd,Pt)-B mixture through the vapour transport. This result enables the possibility of thin films growth using a (Pd,Pt)-B precursor film heat treated in a Li-vapour atmosphere. Preliminary results on thin films growth are introduced. (C) 2009 Elsevier B.V. All rights reserved.

2782. Passivation effects of 4,4'-thio-bis-benzenethiolate adsorbed layers on semiconducting electrodes

Authors: Lazarescu, V; Scurtu, R; Lazarescu, MF; Toader, AM; Volanschi, E

Published: NOV 30 2010, ELECTROCHIMICA ACTA, 55, 8301, DOI: 10.1016/j.electacta.2010.02.004

The effects of the self-assembled layers formed by adsorption of 4 4'-thio-bis-benzenethiol from ethanol solutions on p-S1(111) and p-GaAs(1 00) electrodes were examined by EIS AFM and XPS investigations All the experimental data led to the conclusion that the thio-bis-benzenethiolate film spontaneously formed on Si and GaAs surfaces brings about chemical passivation both in air and in solution as well as strong adsorbate-substrate interactions which affect the semiconductor surface state population and the field effects operating in the interfacial region Semiempirical PM3 molecular orbital calculations showed that electronic interaction of the thiolate film with the two semiconducting electrodes can be understood in terms of changes in the local density of the electronic states at the surface (C) 2010 Elsevier Ltd All rights reserved

2783. CO sensing mechanism with WO3 based gas sensors

Authors: Hubner, M; Simion, CE; Haensch, A; Barsan, N; Weimar, U

Published: NOV 26 2010, SENSORS AND ACTUATORS B-CHEMICAL, 151, 106, DOI: 10.1016/j.snb.2010.09.040

The interaction between CO and WO3 based gas sensors was investigated in operando conditions by using resistance, catalytic conversion and DRIFTS measurements. The experimental results are showing that the sensing involves the reduction of the metal oxide, which is the opposite of the case of SnO2, the other extremely relevant material for semiconducting oxides based gas sensors. (C) 2010 Elsevier B.V. All rights reserved.

2784. Strain and stress tensors of rolled uranium plate by Rietveld refinement of TOF neutron-diffraction data

Authors: Balzar, D; Popa, NC; Vogel, S

Published: NOV 25 2010, MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, 528, 126, DOI: 10.1016/j.msea.2010.06.002

We report the complete macroscopic average strain and stress tensors for a cold-rolled uranium plate, based on the neutron TOF measurements. Both tensors were determined by the least-squares refinement of the interplanar spacings of 19 Bragg reflections. Based on the pole figures, as determined by GSAS, a triclinic sample symmetry of the uranium plate was assumed. Strain and stress are tensile in both the transverse and rolling directions and very small in the normal direction (through the thickness of the plate). Shear strain and stress components are compressive and of significant magnitude. (C) 2010 Elsevier B.V. All rights reserved.

2785. Inelastic transitions and counterflow tunneling in double-dot quantum ratchets

Authors: Moldoveanu, V; Tanatar, B

Published: NOV 10 2010, PHYSICAL REVIEW B, 82, DOI: 10.1103/PhysRevB.82.205312

The ratchet regime of unbiased double quantum dots driven out of equilibrium by an independently biased nearby detector has been theoretically studied using the nonequilibrium Keldysh formalism and the random-phase approximation for the Coulomb effects. When the detector is suitably biased the energy exchange between the two systems removes the Coulomb blockade on the double dot via inelastic interdot tunneling. The energy detuning determines whether the current flows in the same direction as the driving current (positive flow) or in the opposite direction (electronic counterflow). In both cases the intradot transitions lead to negative-differential conductance. Besides the ratchet contribution to the current we also single out a Coulomb drag component.

2786. On the structural, morphological, optical and electrical properties of sol-gel deposited ZnO In films

Authors: Girtan, M; Socol, M; Pattier, B; Sylla, M; Stanculescu, A

Published: NOV 1 2010, THIN SOLID FILMS, 519, 577, DOI: 10.1016/j.tsf.2010.07.006

Indium-doped zinc oxide thin films deposition was performed by the sol-gel technique using homogeneous and stable solutions of zinc acetate 2-hydrate and indium chloride in ethanol Films were spin coated onto glass substrates After drying and after a heat treatment at 450 degrees C highly transparent (80%-90%) films were obtained The effect on the structural morphological optical and electrical thin films properties of the dopant concentration was investigated The temperature dependencies of the electrical conductivity under vacuum and in open atmosphere were analysed and discussed (C) 2010 Elsevier B V All rights reserved

2787. Topological structure of the inter-band phase difference soliton in two-band superconductivity

Authors: Tanaka, Y; Iyo, A; Tokiwa, K; Watanabe, T; Crisan, A; Sundaresan, A; Terada, N

Published: NOV 1 2010, PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS, 470, 1012, DOI: 10.1016/j.physc.2010.05.022

Two-component superconductivity based on the two-band superconductor has a functional topology such as an inter-band phase difference soliton (i-soliton) to realize topological electronics (topolonics). Many gauge field theories are applied to investigate the topology of two-band superconductivity. To ease experimental and electronics applications, these theories should be refined. Weinberg-Salam theory and SU(2) (two-dimensional special unitary symmetry) gauge field theory are proper starting points. An effective extra force field because of the crystal structure and inter-band Josephson interaction, rather than spontaneous symmetry breaking, simplifies the conventional gauge field theory. Crown Copyright (C) 2010 Published by Elsevier B.V. All rights reserved.

2788. Origin of the fast magnetization relaxation at low temperatures in HTS with strong pinning

Authors: Miu, L; Ivan, I; Badica, P; Jakob, G; Miu, D; Mele, P; Matsumoto, K; Mukaida, M; Yoshida, Y; Horide, T; Ichinose, A; Horii, S

Published: NOV 1 2010, PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS, 470, 1129, DOI: 10.1016/j.physc.2010.05.054

The temperature T variation of the normalized magnetization relaxation rate S in high-temperature superconductors (HTS) with strong vortex pinning exhibits a maximum in the low-T range. This was reported for various HTS, and the origin of the faster relaxation at low T appearing in standard magnetization relaxation measurements was usually related to specific pinning properties of the investigated specimens. Since the observed behaviour seems to be characteristic to all HTS with enhanced pinning (generated by random and/or correlated disorder), we show that the S(T) maximum can be explained in terms of classic collective vortex creep. The influence of thermo-magnetic instabilities in the low-T range is also evidenced. The collective (elastic) creep regime is generated by the T dependent macroscopic currents induced in the sample during standard magnetization measurements. (C) 2010 Elsevier B.V. All rights reserved.

2789. Improved critical current densities in thick YBa2Cu3O7-delta multilayer films interspaced with non-superconducting YBa2Cu3Ox nanodots

Authors: Sarkar, A; Dang, VS; Mikheenko, P; Kechik, MMA; Abell, JS; Crisan, A

Published: NOV 1 2010, THIN SOLID FILMS, 519, 879, DOI: 10.1016/j.tsf.2010.08.102

We have fabricated and studied quasi-multilayered thick YBa2Cu3O7-delta (YBCO) films composed of several YBCO layers Interspaced with quasi-layers of non-superconducting YBa2Cu3Ox nanodots grown by Pulsed Laser Deposition on SrTiO3 (100) substrates Magnetization J(c)(B) at 773 K for these thick films showed significant improvement as compared to pure YBa2Cu3O7-delta films of same or even smaller thickness A high J(c)(B) in our quite thick films (1 mu m to 6 mu m) provides a very high total critical current per centimetre of the film width Ic-w Critical current as high as 830 A per cm width in self field and 77 3 K was achieved in 5 mu m thick quasi-multilayer film with non-superconducting YBa2Cu3Ox nanodots Frequency-dependent susceptibility measurements showed also an increase in the pinning potential The angular dependence of Ic-w at 86 5 K in 3 T shows a clear indication of anisotropic pinning centres aligned along the c-direction (C) 2010 Elsevier B V All rights reserved

2790. Increased critical current density and pinning in thick Ag/YBa2Cu3O7-x multilayers

Authors: Dang, VS; Mikheenko, P; Sarkar, A; Kechik, MMA; Abell, JS; Crisan, A

Published: NOV 1 2010, PHYSICA C-SUPERCONDUCTIVITY AND ITS APPLICATIONS, 470, 1241, DOI: 10.1016/j.physc.2010.05.083

We have investigated the superconducting properties of Ag/YBa2Cu3O7-x thick multilayers grown by Pulsed Laser Deposition, and found that the artificial pinning centres induced by Ag nanodots lead to a significant increase in critical current, especially in high applied magnetic fields. Transmission Electron Microscopy showed a columnar growth of YBa2Cu3O7-x, induced by Ag nanodots, while angle-dependent transport measurements revealed the existence of strong, both isotropic and c-axis correlated, artificial pinning centres. (C) 2010 Elsevier B.V. All rights reserved.