Microwave and structural properties of YBa/sub 2/Cu/sub 3/O/sub 7-δ/ films on R-cut sapphire buffered with post-annealed CeO/sub 2/ layer

Abstract

Effects of the post-annealing temperature of CeO/sub 2/ buffer layer on the microwave and structural properties of YBCO films on CeO/sub 2/-buffered sapphire (CbS) were investigated using YBCO films grown on CeO/sub 2/ buffer layer post-annealed at temperatures of 950-1100/spl deg/C. YBCO films on post-annealed CbS appeared to have better properties than those on as-grown CbS with regard to the morphological, structural and microwave properties when the YBCO films were prepared on CeO/sub 2/ buffer layer post-annealed at temperatures of 1000-1050/spl deg/C. The TE/sub 011/ mode Q of a rutile-leaded cavity resonator with YBCO films on CbS post-annealed at 1000-1050/spl deg/C showed the unloaded Q as high as 1.8/spl times/10/sup 5/ at 77 K at 8.6 GHz, a value more than 2 times the corresponding value with the YBCO films replaced by those on as-grown CbS. Also, the decrease in the unloaded Q of a microstrip resonator made of the YBCO film on CbS post-annealed at 1000/spl deg/C appeared less than 3% at 60 K for input power increase of 10 dBm, while the corresponding value was about 24% for a microstrip resonator prepared from the YBCO film on as-grown CbS.