Growth of SrTiOx Buffer Layers and Their Effect on Surface Flatness of YBa2Cu3O7-δ Films on SrTiO3 (110) Substrates

Abstract
SrTiO x (110) homoepitaxial films as buffer layers grown on SrTiO3 (110) substrates are investigated as regards their effect on the surface flatness of high-T c YBa2Cu3O7-δ (YBCO) epitaxial films grown on them. It is observed that SrTiO x films thinner than 30 nm grow laterally so as to decrease the surface roughness of the SrTiO3 substrates, while thicker SrTiO x films grow three-dimensionally with conical islands so as to increase their surface roughness. From the former effect, all-epitaxial YBCO/SrTiO x /YBCO/SrTiO x łSrTiO3 (sub.) tetralayers with the maximum surface roughness (R max) less than 6 nm in a large area are successfully grown.