Microstructure characterization of YBa₂Cu₃O_7-y thin film derived from the metal (Y, Ba, and Cu) naphthenates gels coated on the SrTiO₃ (100) substrate

By postdeposition annealing at temperature range from 650-850°C in the gas mixture containing O₂ and Ar with the oxygen partial pressure of p(O₂) = 10^-4 atm, thin films of YBa₂Cu₃O_7-y (Y123) have been derived from the metal (Y, Ba, Cu) naphthenates gels spin-coated on the SrTiO₃ (100) substrate. The film derived at 700°C has been characterized by means of cross-sectional high resolution electron microscopy (HREM) so as to clarify the details of the microstructures in the derived films. The epitaxial c-axis, a-axis and then nonepitaxial Y123 polycrystal layers were observed successively from the lower to the upper part of the film. The c-axis Y123 thin film, thickness range from 10 nm to 60 nm, was epitaxially formed on the substrate and the a-axis island-shaped grains generated from the c-axis film. The 90° oriented a-and c-axis Y123 grains were found to form meandering grain boundaries; another 90° domain was formed from two differently oriented a-axis grains in which their b- and c-axis are alternatively parallel to each other. A small amount of poly-crystallized Y123 embedded in the amorphous were observed in the upper part of the film.