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/spl deg/C were c-axis oriented and YBCO films deposited on the top at 700/spl deg/C were also c-axis oriented. T/sub /spl alpha//(R=0)=89 K and J/sub c/>10/sup 6/A/cm/sup 2/ were obtained for a 120 nm thick YBCO film deposited on 50 nm thick CeO/sub 2/ layer. High oxygen pressure /spl sim/1 Pa 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.