Growth and formation of the microstructure of YBCO films deposited by magnetron sputtering on fianite substrates

The dependence of the electrophysical and structural properties of the high-$T_c$ YBa$_2$Cu$_3$O$_{7-\delta}$ superconductor films deposited by magnetron sputtering on fianite on the growth temperature is studied. Scanning electron microscopy and X-ray diffraction demonstrate that the layer-by-layer island growth of an YBa$_2$Cu$_3$O$_{7-\delta}$ film occurs on fianite substrates without an additional buffer layer. An increase in the deposition temperature leads to the division of the growing film into regions with strongly different microstructures. The regions of the first type are represented by a high-quality YBa$_2$Cu$_3$O$_{7-\delta}$ layer, and the regions of the second type consists of an YBa$_2$Cu$_3$O$_{7-\delta}$ layer with well-pronounced granule boundaries, which hinder the passage of an electric current.