SURFACE-RESISTANCE, RESIDUAL LOSSES, AND GRANULARITY IN AG-DOPED YBA2CU3O7-DELTA THIN-FILMS

We have studied microwave surface resistance R(s) and residual resistance R(res) in undoped and Ag-doped laser ablated thin-film YBa2Cu3O7-delta mirostrip resonators On LaAlO3 substrates. While the undoped films showed a frequency dependence R(s) is-proportional-to f(p), where p = 1.9 +/- 1, Ag-doped films showed p = 1.6 +/- 1 and 1.4 +/- 1 for 5 and 10 wt % Ag doping, respectively. Lower p values and higher R(res) observed in Ag-doped films indicate a metallic contribution. However, the advantage of Ag-doped films has been shown to be at 77 K at which they not only have a lower R(s) but also a low dR(s)/dT, thus making them superior to undoped films for microwave devices operating at 77 K.