RF POWER DEPENDENCE STUDY OF LARGE-AREA YBCO THIN-FILMS

In an effort to develop HTS superconducting filters with sufficient po wer handling capability for PCS (Personal Communication Services) base station transmit applications, we have undertaken a study of the powe r dependence of large area YBCO thin films on LaAlO3 substrates, We em ployed a coplanar-wave-guide (CPW) resonator technique to obtain the c hanges of loss and inductance versus circulating microwave currents in the films. Data have been collected on uniform large area (2'' diamet er) films grown by coevaporation and off-axis sputtering techniques un der varying deposition conditions, We found correlations between the R F power dependence and other film properties such as penetration depth and crystal structure. The most intrinsic sample, from the coevaporat ion technique, characterized by the smallest penetration depth, good o rthorhombicity and absence of tetragonal phase, shows the least amount of nonlinearity. Such correlations can be used to prescreen films for fabrication and monitor the film production line, However, films from coevaporation and off-axis sputtering show very distinct power depend ent behaviors.