Microwave and structural properties of YBa2Cu3O7-delta films on R-cut sapphire buffered with post-annealed CeO2 layer

Effects of the post-annealing temperature of CeO2 buffer layer on the micro wave and structural properties of YBCO films an CeO2-buffered sapphire (CbS ) were investigated using YBCO films grown on CeO2 buffer layer post-anneal ed at temperatures of 950 - 1100 degreesC. YBCO films on post-annealed CbS appeared to have better properties than those on as-grown CbS with regard t o the morphological, structural and microwave properties when the YBCO film s were prepared on CeO2 buffer layer post-annealed at temperatures of 1000 - 1050 degreesC. The TE011 mode Q of a rutile-loaded cavity resonator with YBCO films on CbS post-annealed at 1000 - 1050 degreesC showed the unloaded Q as high as 1.8 x 10(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 Nm on CbS post-annealed at 1000 degreesC appeared less than 3 % at 60 K for input power increase of 10 dBm, while the corresponding value was ab out 24 % for a microstrip resonator prepared from the YBCO film on as-grown CbS.