Microwave surface resistance of iinpatteraed and patterned Yba_2Cu_3O_(7-δ) thin films produced by pulsed laser deposition

摘要

High quality epitaxial thin films of Yba_2Cu_3O_(7-δ)(YBCO) deposited by pulsed laser deposition were first chracterised at 15 GHz using a dielectric resonator technique. They were then patterned into coplanar resonators and characterised at 8 and 16 GHz. The values of surface resistances are relatively unaffected by the patterning process and at 15 GHz are around 140μΩ at 20 K, rising to 780μΩat 77K. The coplanar resonator technique allows us to study the effects of high microwave fields owing to the peaking of the microwave current at the patterned film edges, and we find that significant non-linearity occurs only for edge current densities in excess of the measured dc critical current density.