IMPROVED MICROWAVE PERFORMANCE OF AG-DOPED Y1BA2CU3O7-DELTA THIN-FILMMICROSTRIP RESONATORS

Microwave transmission properties of undoped and Ag-doped laser ablate d thin film Y1Ba2Cu3O7-delta microstrip resonators have been studied b oth on [100] MgO and [100] LaAlO3 substrates at X-band frequencies. Wh ile the Q factor and microwave surface resistance, R(s) of undoped fil ms showed better performance on LaAlO3 as compared to that on MgO, Ag- doped films on LaAlO3 showed far greater improvement as reflected not only by a decrease in R(s) but also by a total absence of its microwav e power dependence up to 13 dBm at 77 K. These results are explained a s due to the influence of Ag in increasing the grain size and grain al ignment and thus, significantly decreasing the density of grain bounda ry weak links which are known to affect the microwave transmission in high temperature superconductor films.