Influence of critical parameters in the synthesis of superconducting thin films of YBa2Cu3O7-x on (100) SrTiO3 by glow discharge sputtering

A systematic study on the influence of process parameters such as substrate temperature, gas composition and ion current in the synthesis of superconducting thin films of YBa2Cu3O7-x on (100) SrTiO3 by glow discharge or high pressure sputtering is presented for the first time. This method offers a route to grow good quality thin films at substrate temperature as low as 923-933 K in a single uninterrupted cycle. The films grown at an optimum substrate temperature of 933 K and an ion current of 50 mA show a transition temperature at zero resistance of about 87 K, a transition width of 1.5 K and critical current density of about 106 A.cm-2 at 77 K, in zero magnetic field. These films show a characteristic basket weave microstructure, whereas the films grown at larger ion currents show an overgrowth morphology. An optimum oxygen content in the argon-oxygen gas mixture ratio of 6:1 yields films of superior quality. The improvement in the superconducting properties of the films in relation to the quality of the target material used is also discussed. (author). 37 refs., 16 figs