Compositional effects in YxBayCuzO7minus;dgr;thin films prepared by metalorganic chemical vapor deposition

摘要

We report on effects of composition onto superconducting and structural properties of Yhyphen;Bahyphen;Cuhyphen;O thin films, prepared by a carrierhyphen;gas free metalorganic chemical vapor deposition technique. Thin films with critical temperaturesTcge;90 K, transition widths Dgr;Tcle;1 K, and critical current densitiesjc(T=77 K,B=0 T)ge;106A/cm2can be prepared by this method. Here we report on a strong dependence of theTcon the ratio of Ba/Cu. For Ba/Cu2 the surfaces show CuO precipitates, increasing in quantity and size with increasing concentration of Cu. An excess of Y leads to oriented inclusions of cubic Y2O3. A deficit of Y and Cu causes an expansion of thechyphen;lattice parameter. To investigate the influence of Y2O3and CuO precipitates on the pinning potential, resistive transitions in magnetic fields up to 12 T were measured and interpreted by a thermal activated fluxhyphen;creep model. These measurements indicate the inefficiency of both, inclusions and precipitates, on the enhancement of the pinning potential.