Large grain size obtained by substrate directly heating for YBCO epitaxial films

It is very important for high temperature superconducting electronic devices to increase the grain size of YBCO epitaxial films because it can effectively reduce the defects and improve the probability of successful preparation of Josephson junction. In this study, YBa₂Cu₃O_7–δ (YBCO) films with grain size in excess of 1.5 μm were successfully prepared by the directly heating SrTiO₃ substrates coated by SiC on their back. Interestingly, the grain size of YBCO film is enhanced greatly by this directly heating method, and the critical temperature T_C and critical current density J_C of YBCO films are as high as 91.5 K and 3.5 MA/cm², respectively. Compared with the traditional indirect heating method, which involves applying silver paste and then using a heat soaking block (e.g. Inconel 600), this direct heating method effectively enhances the grain size of YBCO film and the possibility of successful preparation of Josephson junction.