Preparation and characteristics of superconducting cuprate thin films: Nd(2-x)Ce(x)CuO4 and substrated Bi-system

Characteristics of the electron-doped-type Nd(sub 2-x)Ce(sub x)CuO4 system and substituted Bi-system were studied using the high quality thin film samples grown by rf magnetron sputtering and/or subsequent heat treatment. The Nd(sub 2-x)Ce(sub x)CuO4 samples with excellent superconducting properties were obtained in thin films and their optical and X-ray photoelectron spectroscopy (XPS) studies were performed with regard to the Ce content and reducing treatment. Substituted BiSr-Ln-Cu-O thin films were prepared and growth conditions for Bi-system with 2-2-1-2 and 2-2-2-2 phases were found. Moreover, a new 2-2-1-2 phase in the simple Bi-Sr-Cu-O system was fabricated by thin film processing and 80 K superconductivity was obtained

Preparation and characteristics of superconducting cuprate thin films: Nd(2-x)Ce(x)CuO4 and substituted Bi-system

Characteristics of the electron-doped-type Nd(2-x)Ce(x)CuO4 systems and substituted Bi2(Sr,Ln)3Cu2Oy system were systematically studied using the high quality thin-film samples. The Nd(2-x)Ce(x)CuO4 thin films with various Ce concentrations, x, were prepared by RF magnetron sputtering on SrTiO3 heated at around 500 C. After subsequent annealing at 1100 C in air, the films showed the c-axis orientation normal to the substrates. By means of the reducing treatment (annealing in a vacuum), superconductivity was induced for the films with 0.14 is less than or equal to x is less than or equal to 0.18. The superconductivity and transport properties of the films were strongly affected by the reducing treatment. The x = 0.15 film exhibited a sharp superconducting transition with zero resistivity at 22 K, in consistent with the diamagnetic properties. The resistivity of the films was fairly low with metallic characteristics, and the sight of the Hall coefficient was negative in the normal state. On the other hand, the normal-state optical measurements showed that the undoped Nd2CuO4 is a semiconductor with a charge transfer gap of 1.3 eV, and that, when Ce ions were doped, a plasma reflection due to the free-carriers came to be seen with the plasma frequency of 1.07 eV for 0.14 is less than or equal to x is less than or equal to 0.18. Moreover, x ray photoemission study revealed that the Cu valence of the film decreased for 2(+) for x = 0 to 1(+) for x = 0.15. These physical properties are in contrast with those of hole-doped-type cuprate superconductors. Bi2(Sr,Ln)3Cu2Oy thin films were also prepared on MgO substrates heated at 600 to 700 C by similar methods. It was found that the growth conditions for Bi-systems with two CuO2 planes were different for each composition and species of lanthanoid in the films. Moreover, preparation of Bi-system with three CuO2 planes was very difficult when lanthanoid atoms were doped in the system. Their electric transport properties and x ray photoemission spectroscopy were investigated. Carrier concentration and Cu valence were discussed with regard to the superconductivity

Magnetic properties of BiMnO3 nanoparticles in SBA-15 mesoporous silica

Nanoparticles of multiferroic material BiMnO3 were synthesized in the pores of the mesoporous silica SBA-15 and their magnetic properties were investigated. The powder X-ray diffraction pattern for the nanoparticles at room temperature was similar to that for bulk crystals with monoclinic symmetry. The particle size of the nanocrystals was estimated to be about 14 nm using Scherrer\u27s equation. The temperature dependence of the DC susceptibilities for the nanoparticles showed superparamagnetic behavior. The susceptibility and thermoremanent magnetization exhibited the ferromagnetic feature and the ferromagnetic transition temperature was almost same to that for bulk crystals, approx 100 K. However, the Weiss temperature Θ was evaluated as the negative value and the magnetization curve showed antiferromagnetic behavior. The results suggest the antiferromagnetic properties appeared prominently in the nanoparticles.Proceedings of the 25th International Conference on Low Temperature Physics (LT 25), August 6-13, 2008, Amsterdam, Netherland

Photoemission From Small Palladium Clusters Supported on Various Substrates

The core-electron binding energy obtained for small Pd clusters supported on various substrates is greater than that obtained for bulk Pd metal. The shifts of the core-electron binding energy and the core-valence-valence Auger-electron kinetic energy for small Pd clusters on the conductive amorphous carbon substrate are in good agreement with those calculated by the thermodynamic model using Miedema’s semiempirical theory. Both experimentally and theoretically, the positive shift of the Pd core-electron binding energy with decreasing coverage is shown to be due to the photoemission initial-state effect. The shifts of the Pd core-electron binding energy with the coverage for small clusters on the semiconductive InSb and InP substrates are primarily due to the initial-state effect. The ratio of the photoemission initial-state-effect change to the photoemission final-state-effect change decreases with an increase of the polarizability of the substrate. The photoemission final-state effect predominantly arises from the positive shift of the Pd core-electron binding energy with decreasing coverage on the insulating SiO2 and Al2O3 substrates. The changes in the terms of the extra-atomic relaxation energy for the Pd core hole and the potential energy of the Pd core electron differ for each substrate. The change in the extra-atomic relaxation energy for the Pd core hole varies with the change of the polarizability of the substrate. The change in the potential energy of the Pd core electron correlates with the difference in electronegativities of the substrate components

Interfacial solid‐state reaction at thermally oxidized In1−xGaxAsyP1−y alloys

The interfacial reaction between thermally oxidized In1−xGaxAsyP1−y and an In1−xGaxAsyP1−y epilayer was studied using Raman and x-ray photoelectron spectroscopy (XPS) analyses. In Raman spectra, it was found that the appearance of the phonon modes, i.e., the first-order longitudinal (LO) and transverse-optical (TO) modes for crystalline arsenic, was due to the In1−xGaxAsyP1−y -oxide interfacial reaction. The XPS analyses showed that this reaction corresponded to the GaAs-oxide interfacial reaction, i.e., As2O3+2GaAsGa2O3+4As. Furthermore, the reaction depends on the composition y of In1−xGaxAsyP1−y, which may be due to the enhancement in the initial transient reaction by thermal damage of In1−xGaxAsyP1−y occurring at the interface. Journal of Applied Physics is copyrighted by The American Institute of Physics

Enhanced Conductivity of Zinc-oxide thin-films by Ion-Implantation of Hydrogen-atoms

Enhancement of the conductivity of zinc oxide through doping with hydrogen atoms was examined by using ion implantation of highly resistive thin films deposited by rf magnetron sputtering at room temperature. With a doping of 1 X 10(17) atoms cm-2, the conductivity after annealing at 200-degrees-C in an N2 atmosphere at 1 atm rose from the initial 1 X 10(-7) OMEGA-1 cm-1 to 5.5 X 10(2) OMEGA-1 cm-1

Cuinse2 Homojunction Diode Fabricated by Phosphorus OP9

Homojunction diodes were fabricated by doping of phosphorus to n-type Cu-In-Se thin films. The junction prepared by P implantation at the energy of 50 keV with the dose of 1 x 10(15) ions/cm 2 showed a rectification ratio of more than 100. Conduction in Cu-In-Se thin films, whose crystal structure is of the chalcopyrite type, changes from n- to p-type in such a way that group V elements (N, P, Sb, or Bi) substitute for Se in the film

Characterization of Ingaasp surface Corrugation Used for Distributed Feedback Lasers by Means of Raman－Spectroscopy

Thermally deformed surface corrugations on both an InP substrate and an InGaAsP layer have been analyzed by means of x-ray photoelectron spectroscopy and laser Raman spectroscopy. From the spectra of the deformed surface corrugations on an InP substrate on which a GaAs wafer was placed during its heat treatment, it has been found that material formed in the grooves is an InGaAsP alloy single crystal. Applied Physics Letters is copyrighted by The American Institute of Physics

Optical and dielectric properties of quantum-confined SrBi2Ta2O9 mesocrystals

We report an increase in optical absorption peak energy from 3.9 to 5.3 eV, and a lowering of dielectric constant maximum temperature from 320 to 180 °C for SrBi2Ta2O9 mesocrystals

Interfacial Solid－State Reaction at Thermally Oxidized in1－Xgaxasyp1－Y Alloys

The interfacial reaction between thermally oxidized In1−xGaxAsyP1−y and an In1−xGaxAsyP1−y epilayer was studied using Raman and x-ray photoelectron spectroscopy (XPS) analyses. In Raman spectra, it was found that the appearance of the phonon modes, i.e., the first-order longitudinal (LO) and transverse-optical (TO) modes for crystalline arsenic, was due to the In1−xGaxAsyP1−y -oxide interfacial reaction. The XPS analyses showed that this reaction corresponded to the GaAs-oxide interfacial reaction, i.e., As2O3+2GaAsGa2O3+4As. Furthermore, the reaction depends on the composition y of In1−xGaxAsyP1−y, which may be due to the enhancement in the initial transient reaction by thermal damage of In1−xGaxAsyP1−y occurring at the interface. Journal of Applied Physics is copyrighted by The American Institute of Physics