[en] The aim of this paper is: Characterisation of oxygen nonstoichiometry (7-x) and oxygen diffusion (D_o) in YBa₂Cu₃O_7-x-ceramics. Separation of electronic (σ_e) and ionic (σ_o2-) conductivities. Determination of the electronic structure at the surface and in the bulk of epitaxial YBa₂Cu₃O_7-x-films. Analysis of chemical reactions between YBa₂Cu₃O_7-x-films and substrates, electrodes, pasivation layers etc. with the aim of preparing epitaxial YBa₂Cu₃O_7-x-films on Si-substrates with high values for T_c and J_c. The results make it possible to prepare longterm stable epitaxial YBa₂Cu₃O_7-x-films on Si and to control the oxygen content in YBa₂Cu₃O_7-x thermodynamically or kinetically by controlled solid state diffusion. (orig./MM)

No abstract available

[en] Low temperature sintering of YBa₂Cu₃O_y ceramics by various Ag compounds was studied by in situ resistivity measurement using a four-probe method and silver ionic conductivity measurement using four silver ion conduction electrodes of Ag-β double-prime-Al₂O₃. Even silver ionic compounds promoted sintering, indicating that the Ag⁺ ion promotes sintering in the grain boundaries. The activation energies of Ag⁺ ionic conductivities of the Ag-added samples (0.2 - 1.4 eV) were much lower than those in the YBa₂Cu₃O bulk (2.3 - 2.5 eV), indicating that the Ag⁺ ion easily diffuses in the grain boundaries at low temperature

No abstract available

No abstract available

No abstract available

[en] Structures and stability ranges of the YBa₂Cu₃O_7-x/Si interface were studied with AES, SIMS, XPS, and TEM. For silicon substrates, the formation of Ba silicates can be detected which even at T=550 K leads to reduced Tc values and non-epitaxial growth of YBa₂Cu₃O_7-x (YBCO). Yttria stabilized zirconia (YSZ) buffer layers between Si substrates and YBCO lead to epitaxial overlayer growth and improved superconducting properties whereas CaF₂ is not suitable for this purpose. - Furthermore, SiO₂, YSZ, and CaF₂ were tested for their suitability as passivation layers against the influence of humidity. As-passivated superconducting films are stable up to 500 K in 100% humid air. Above this temperature the superconductor is reduced chemically. Non-passivated films, however, are stable only at temperatures below 450 K and are destroyed totally in humid air at higher temperatures. (orig.)

[en] Angle-dependent x-ray photoemission spectra (XPS) of epitaxial thin-film YBa₂Cu₃O_7-x show characteristic reversible and distinct changes with different surface treatments. These changes are analyzed by applying a new model for the quantitative XPS analysis, which takes into consideration the anisotropic structure of c-axis-oriented YBa₂Cu₃O_7-x. The analysis makes it possible to differentiate between different elemental compositions of the outer layers in the surface unit cell. Evaluations of our experimental data indicate that only surfaces with a nominal BaO and CuO layer composition exist in the outermost atomic layer

[en] Ferromagnetic resonance (FMR) and torsion magnetometry were carried out on 60 Ni/40 Fe (111) oligatomic thin films (2.4 <= Dsub(M) <= 9.4 atomic layers) at temperatures between 123 K and 373 K. A comparative discussion of the results is given. Anisotropies of the films, determined by both methods, agree roughly. Approximately, they show a 1/Dsub(M)-dependence on the film thickness, as expected from an interpretation as surface anisotropy. FMR is shown to be a useful experimental tool for the investigation of oligatomic ferromagnetic films. Informations may be taken from the resonance field, line width, line shape and total absorbed microwave power. The magnetic moment must be taken from magnetometry. (orig.)

[en] The scattering processes of slow electrons in high-resolution electron-energy-loss spectroscopy (HREELS) at the surface of organic solids have been studied, both theoretically and experimentally. We used selectively deuterated molecules which were prepared in highly ordered films by the Langmuir-Blodgett (LB) technique. In the framework of a microscopic approach the intensity ratios for CD- and CH-stretching vibrations in the dipolar and impact limit were estimated. The broad angular distribution of elastically reflected electrons scattered at organic surfaces as well as the anisotropy of the films were taken into account. In a first set of experiments the influence of the substitution of hydrogen by deuterium on the intensity of the corresponding methyl and methylene stretching vibrations was measured. Comparison of the results with the theoretical considerations supports a dipolar-dominated scattering at around 5 eV with an increase of the impact contribution at lower energies. Second, the information depth and its dependence on the impact energy of the electrons was studied. The strong increase in the information depth towards lower electron energies can be correlated with a decrease of the dipolar scattering intensity and an enhancement of short-range interaction. (orig.)