MICROSTRUCTURE AND MICROWAVE PROPERTIES OF YBA2CU3O7-DELTA THIN-FILMS GROWN ON NDGAO3

High-quality YBa2Cu3O7-delta thin films have been grown on NdGaO3(001) substrates by in situ laser ablation. The best transition temperature determined by AC susceptibility is 88.9 K and transition width is as narrow as 0.4 K. Critical current density of 1.2 x 10(6) A/cm2 at 77 K was obtained. However, the loss tangent of this substrate is measured to be 3 x 10(-4) at 77 K and 5 GHz which is ten times poorer than that of LaAlO3. A 2.3 GHz resonator made from films on NdGaO3 exhibited a low power Q of 4500 which is very close to the calculated limit based on the loss tangent data. The microwave performance is thus severely limited by the substrate loss in our test geometries.