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

Effects of the post-annealing temperature of CeO₂ buffer layer on the microwave and structural properties of YBCO films on CeO₂-buffered sapphire (CbS) were investigated using YBCO films grown on CeO₂ buffer layer post-annealed at temperatures of 950-1100°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 CeO₂ buffer layer post-annealed at temperatures of 1000-1050°C. The TE₀₁₁ mode Q of a rutile-leaded cavity resonator with YBCO films on CbS post-annealed at 1000-1050°C showed the unloaded Q as high as 1.8×10⁵ 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°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