Laser processing of YBCO thin films on sapphire for microwave applications

Laser ablation has been used to fabricate YBa/sub 2/Cu/sub 3/O/sub 7-x/(YBCO) thin film on sapphire substrates for microwave applications. The Interfaces between the YBCO laser ablated thin films and the r-plane Al/sub 2/O/sub 3/ substrates have been investigated by a transmission electron microscopy (TEM) and an Auger electron spectroscopy (AES) depth profile. The PrBa/sub 2/Cu/sub 3/O7-x (PBCO) buffer layer has been used to prevent the interdiffusion. The interfaces of YBCO/Al/sub 2/O/sub 3/ and YBCO/PBCO/Al/sub 2/O/sub 3/ have been compared. The intermediate diffusion layer in the YBCO film deposited on bare sapphire was visible between the film and the substrate but no diffusion layer between the YBCO/PBCO thin film and the substrate was observed directly by the cross-section image of TEM. The thickness of the diffusion layer on bare sapphire is about 300 /spl Aring/. This result of TEM is consistent with that of AES depth profile. We have fabricated a perturbed superconducting ring resonator on PBCO buffered sapphire for the microwave application. A fundamental resonance peak split was observed in the frequency range of 7.0-8.4 GHz.