Structure of superconducting thin films of YBa2Cu3O7-x grown on SrTiO3 and cubic zirconia

Thin films of the superconductive oxide YBa2Cu3O7-x have been made by electron-beam coevaporation of the metals in an oxygen atmosphere onto single-crystal [001]-oriented SrTiO3 and yttria-stabilized zirconia (YSZ) substrates. The oxide films were superconducting in the as-deposited state (Tc = 81-83K, Jc = 10(6) A/cm2 at 4.2K). Bright-field imaging, selected-area diffraction (SAD), and high-resolution imaging in the transmission electron microscope were used to characterize the microstructure of these films. All of the films were polycrystalline. On SrTiO3 the films were oriented, for the most part, with [110] parallel to the substrate surface. On YSZ, two microstructures were observed: one with smaller rectangular grains oriented with (100) or (010) parallel to the substrate surface and the other with (001) parallel to the surface (i.e., c-axis up).