INTERFACE ANALYSIS OF EPITAXIAL YBA2CU3O7 THIN-FILMS DEPOSITED ON SAPPHIRE (AL2O3) WITH YSZ BUFFER LAYERS

Single-orientation, c-oriented thin films with high critical transport currents (j(c) > 5 X 10(5) A/cm2 at 77 K) were deposited on sapphire with YSZ buffer layers. High-resolution transmission electron microscopy was used to image the various interfaces. At the YSZ-YBa2Cu3O7 interface, a BaZrO3 intermediate layer of 3-5 nm thickness was observed. The intermediate layer was highly oriented and grew on the single-crystalline buffer layer via the diffusion of Ba into the YSZ. The Al2O3-YSZ interface was planar on the atomic scale, and local mechanical strain fields at the interface being due to the mismatch between (012)-Al2O3 and (220)-YSZ lattice planes were found.