a-axis oriented YBa2Cu3Oy thin films grown on novel buffer layers

Preferable growth conditions for preparing a-axis oriented YBa2Cu3Oy (YBCO) and PrBa2Cu3Oy(PBCO) thin films on SrTiO3 substrates were investigated. The structural analysis of thin films deposited at various substrate temperatures and growth rates revealed that cubic structure films with high crystallinity were grown at relatively low substrate temperatures in the Y-Ba-Cu-O system and at a high deposition rate in the Pr-Ba-Cu-O system, respectively. Although the a-axis orientation growth of YBCO was found to be enhanced on the cubic-YBCO film with excellent lattice matching with YBCO, a large density of segregated particles was observed both in the cubic-YBCO films and the YBCO films grown on them. The surface morphology of a-axis oriented YBCO thin films was significantly improved by utilizing a cubic-YBCO/cubic-PBCO bilayer buffer. The surface roughness of the 250 nm thick a-axis oriented YBCO thin film grown on the bilayer buffer was confirmed to be less than 25 nm and the T-c(onset) reached 90 K.