Fabrication process of YBCO thin film starting from amorphous film for microstrip line device

We investigated the process for fabricating YBa2Cu3Oy (YBCO) thin film microstrip lines from amorphous thin films. First, we made amorphous YBCO thin films and then post-annealing was carried out. The amorphous 300-nm-thick YBCO thin films were deposited on a CeO2 buffered r-Al2O3 substrate by pulsed laser deposition. The 50-nm-thick CeO2 buffer layer was made by a facing target sputtering system. We examined the optimal conditions of the post-annealing process by using a two-step crystallization process. The heating rate of the first step was set to 360 K/min until 1023 K, and then the heating rate of the second step was set to 20 K/min until 1073 K. The oxygen pressure was kept to 3000 Pa at 1073 K for 210 min. From the XRD measurement, we observed that the YBCO thin films grew c-axis orientation on the CeO2/r-Al2O3 substrate. Both YBCO and CeO2 φ-scan peaks showed four-fold symmetry and rotated 45 degrees between YBCO (102) grain axis and CeO2 (220) grain axis. The surface roughness, Δφ, and Δφ of YBCO thin films were 35.12 nm, 0.89 degree, and 1.51 degree, respectively. We found these to be the optimal post-annealing conditions in which to make a single phase of YBCO films with Tc of 87 K from amorphous YBCO thin films. Therefore, our process is useful to make high-quality YBCO microstrip lines.