GROWTH OF SRTIOX BUFFER LAYERS AND THEIR EFFECT ON SURFACE FLATNESS OF YBA2CU3O7-DELTA FILMS ON SRTIO3(110) SUBSTRATES

SrTiOx (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-delta (YBCO) epitaxial films grown on them. It is observed that SrTiOx films thinner than 30 nm grow laterally so as to decrease the surface roughness of the SrTiO3 substrates, while thicker SrTiOx films grow three-dimensionally with conical islands so as to increase their surface roughness. From the former effect, all-epitaxial YBCO/SrTiOx/YBCO/SrTiOx//SrTiO3 (sub.) tetralayers with the maximum surface roughness (R(max)) less than 6 nm in a large area are successfully grown.