SPUTTER-DEPOSITION OF LARGE-AREA YBA2CU3O7-DELTA THIN-FILMS

The utilization of a sputtering system equipped with three planar magn etron guns in off-axis geometry results in very homogeneous films spre ading an area of two inches in diameter. During deposition the substra te is directly heated by the thermal radiation of quartz lamps. No the rmal contact is required between the heater and the substrate. The tem perature of the substrate surface is controlled using an infrared pyro meter with adapted emissivity calibration taking into account the diff erent optical properties of the film and the substrate. In DC resistan ce measurements the films show a T-c around 90 K and a superlinear tem perature dependence in the normal state. The resistance ratio Gamma = R(300K)/R(100K) ranges up to 4.0 and the resistance at T=0 clearly ext rapolates to negative values.