LONG-TIME BEHAVIOR OF THE HIGH-FREQUENCY PROPERTIES OF YBCO THIN-FILMS

The long-time behaviour of the high-frequency properties of c-axis ori ented YBa2Cu3O7-delta (YBCO) thin films was studied using photolithogr aphically patterned coplanar waveguide resonators. The temperature and power dependence of the surface resistance (R(s)), the transition tem perature (T(c)) and the critical current density (j(c)) were monitored over time periods of more than one year while keeping the samples at ambient air. There was no evidence for a significant degradation for s amples with j(c) (77 K) as high as 4 x 10(6) A/cm2 as well as for film s exhibiting a granular high-frequency behaviour with j(c) (77 K) of 1 x 10(6) A/cm2. The results are discussed with respect to the reactivi ty of YBCO thin-film surfaces to atmospheric components as observed by X-ray photoelectron spectroscopy (XPS).