Preparation of YBCO films on sapphire with CeO sub(2) deposited by ion beam sputtering

Although sapphire has superior high frequency properties, an adequate buffer layer is required to form a high-Tc film. We deposited a CeO sub(2) buffer layer by ion beam sputtering in high oxygen pressure, and investigated the influence of the deposition conditions on the superconducting properties of YBa sub(2)Cu sub(3)O sub(7-y) (YBCO) films. CeO sub(2) films deposited at higher than 600 degree C were c-axis oriented and YBCO films deposited on the top at 700 degree C were also c-axis oriented. T sub(ce)(R identical with 0) identical with 89K and J sub(c) > 10 super(6)A/cm super(2) were obtained for a 120nm thick YBCO film deposited on 50nm thick CeO sub(2) layer. High oxygen pressure approx. 1Pa is desirable. Grain boundary Josephson junctions were also successfully fabricated on bicrystal sapphire substrate. It was found that high pressure ion beam sputtering is a promising method for superconductive electron devices.