Microwave properties of YBCO thin films

We have measured the microwave properties of high quality YBCO thin films using a copper cavity (87 GHz) and a dielectric resonator (19 GHz) for unpatterned films as well as a coplanar resonator (5, 8, 10, 15 and 16 GHz) for patterned films. For the patterned films the surface resistance (R/sub S/) and non-linear effects were studied as a function of temperature below T/sub C/. For practical applications, the assessment of non-linear effects in the surface resistance are of great importance. The best films showed R/sub S/ approximately constant up to microwave peak current densities of the order of the dc critical current density. The measurements were performed on samples fabricated by a number of different techniques.>