Y1BA2CU3O7-X THIN-FILMS GROWN ON SAPPHIRE WITH EPITAXIAL MGO BUFFER LAYERS

We have developed a process for growing as-deposited Y1Ba 2Cu3O7-x (YBCO) thin films on R-plane sapphire substrates with an intermediate layer of epitaxial MgO. The orientation of the layers has YBCO (001) parallel to MgO (100) which is parallel to the substrate normal. These films are superconducting by 88.5 K and exhibit J c=1×106 A/cm2 at 77 K and 2.5×107 A/cm2 at 4.2 K. The MgO layers may be grown at temperatures as low as 370 °C and are very stable in air. Little or no diffusion occurs between the substrate and the two layers as measured by Auger profiling.