Preparation and characterization of NdBa/sub 2/Cu/sub 3/O/sub y/ thin films

C-axis oriented epitaxial NdBa/sub 2/Cu/sub 3/O/sub y/ thin films on [100] SrTiO/sub 3/ substrates were prepared by off-axis rf sputtering. Thin films with T/sub c0/=90 K in a deviation of 0.5 K were prepared reproducibly under the optimal depositing conditions. A parabolic relation of T/sub c0/ to c-axis lattice parameter corresponding to a typical electronic phase diagram for high-T/sub c/ superconductors was observed, indicating an optimal oxygen content for the best superconductivity. The oxygen out-diffusion and thermal expansion of the films were studied by an in-situ high temperature x-ray diffraction.