CeO$_2$ 완충층에 대한 고온 열처리가 CeO$_2$ 완충층을 지닌 R-cut 사파이어 기판 우에 성장된 YBa$_2Cu_3O_{7-{\delta}}$ 박막의 표면상태에 미치는 영향

Effects of High-temperature Annealing of CeO$_2$ Buffer Layers on the Surface Morphology of YBa$_2Cu_3O_{7-{\delta}}$ Films on CeO$_2$-buffered R-cut Sapphire Substrates

YBa$_2Cu_3O_{7-{\delta}}$ (YBCO) films grown on CeO$_2$-buffered r-cut sapphire substrates (CbS's) were prepared and their structural and electrical properties were measured. Post-annealed CeO$_2$ films were used as buffer layers for the experiments. It turned out that the YBCO films grown on post-annealed CbS's had the rms roughness of less than 20 ${\AA}$ and peak-to-peak roughness of about 30 ${\AA}$ when the YBCO film thickness was 3000 ${\AA}$. Meanwhile, YBCO films on in-situ grown CeO$_2$ buffer layers on r-cut sapphire substrates appeared to have the peak-to-peak roughness of more than 450 ${\AA}$. X-ray diffraction data revealed that the YBCO flms were epitaxially grown along the c-axis with the typical FWHM of(005) ${\theta}$ -2 ${\theta}$ peak about 0. 16 $^{\circ}$ and ${\Delta}$ ${\omega}$ of the (005) peak about 0.5 $^{\circ}$. T$_c$ > 87 K, ${\Delta}$T < 1 K and R(look)/R(100K) ${\ge}$3 were observed from the YBCO films. Applicability of the YBCO films for high-frequency applications was described.