MICROSTRUCTURE AND SUPERCONDUCTING PROPERTIES OF THIN-FILMS OF YBCO ON (100) MGO SUBSTRATE GROWN BY GLOW-DISCHARGE DEPOSITION

Direct growth of YBa2Cu3O7-x superconducting thin films on (100) MgO s ingle crystal substrate has been achieved by a glow discharge sputteri ng process from a single target of stoichiometric compound. Films have been deposited in the temperature range of 923-973 K and oxygenated a l 673 K in a single uninterrupted cycle. The YBa2Cu3O7-x films prepare d under optimum processing conditions have a strong texture (c-axis pe rpendicular to film plane), have transition temperatures at zero resis tance of 86 K and the width of transition of about 2 K. The films have transport critical current density of about 5 X 10(5) A/cm2 at 77 K a nd 2 X 10(6) A/cm2 at 50 K at zero magnetic field. The processing cond itions and relation between the microstructures and superconducting pr operties have been studied in detail. It is shown that the microstruct ure corresponding to the best superconducting properties is a basket w eave microstructure at the resolution limit of an optical microscope.