| High-T{dollar}sb{lcub}rm c{rcub}{dollar} superconducting thin films of YBa{dollar}sb2{dollar}Cu{dollar}sb3{dollar}O{dollar}sb{lcub}7{lcub}-{rcub}delta{rcub}{dollar} were synthesized by the electron beam co-evaporation method. Guided by various characterization methods, optimum deposition parameters, substrates, and annealing conditions were found. The best films were obtained when they were deposited onto (100) SrTiO{dollar}sb3{dollar} at ambient substrate temperature and annealed in flowing oxygen. Resistive transitions were measured by four point probe method. Samples were analyzed by x-ray diffraction, electron microprobe, Rutherford backscattering, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Critical current densities (J{dollar}sb{lcub}rm c{rcub}{dollar}) were measured by transport and magnetization method.; Theory for upper critical field and thermodynamic fluctuations in layered superconductors is reviewed. Upper critical field (H{dollar}sb{lcub}rm c2{rcub}{dollar}) and fluctuation-enhanced conductivity were measured for highly oriented thin films. The H{dollar}sb{lcub}rm c2{rcub}{dollar} results demonstrate the intrinsic anisotropy in this layered superconductor. Using these data, the intra- and inter-layer coherence lengths {dollar}xisb{lcub}rm ab{rcub}{dollar}(0) and {dollar}xisb{lcub}rm c{rcub}{dollar}(0) are determined. The shape of the resistive transitions in applied magnetic fields and the positive curvature of the initial slope of H{dollar}sb{lcub}rm c2{rcub}{dollar} are considered in view of flux creep and critical fluctuations. The results of fluctuation-enhanced conductivity above T{dollar}sb{lcub}rm c{rcub}{dollar} have shown a 3D to 2D crossover in accord with the Lawrence-Doniach theory for layered superconductors coupled by Josephson tunneling. The effective dimensionality of the superconductivity in YBa{dollar}sb2{dollar}Cu{dollar}sb3{dollar}O{dollar}sb{lcub}7{lcub}-{rcub}delta{rcub}{dollar} is discussed.; Another class of high-T{dollar}sb{lcub}rm c{rcub}{dollar} oxide superconducting thin films of Bi-Sr-Ca-Cu-O was synthesized and characterized. This material was deposited onto (100) SrTiO{dollar}sb3{dollar} in a similar way to YBa{dollar}sb2{dollar}Cu{dollar}sb3{dollar}O{dollar}sb{lcub}7{lcub}-{rcub}delta{rcub}{dollar} and oxygen post-annealed. One dimensional superstructure was observed in this material by x-ray diffraction and TEM. In addition, two dimensional superlattice structure was observed by TEM. |
