Superconducting YBa 2Cu 3O 7 films grown on TiO 2 buffer layers derived from various processes

Abstract

YBa 2Cu 3O 7 (YBCO)/TiN and YBCO/TiO 2 bilayer structures have been prepared on SrTiO 3 (STO)(1 0 0) substrates by in situ pulsed laser deposition (PLD). The TiN films were originally intended to serve as the lower contact electrode for studying the c-axis transport properties of YBCO thin films. It was found that, under the optimum conditions of depositing YBCO thin films, the TiN(1 0 0) layer was oxidized and transformed into rutile TiO 2(1 1 0) film. On the other hand, pure anatase TiO 2(0 0 1) films were prepared by PLD using a rutile TiO 2(1 1 0) substrate as the target. YBCO films grown on both phases of TiO 2 films show virtually the same transport properties of typical good quality single-layer YBCO films. Comparative studies of depositing YBCO films directly onto a dc-sputtered TiO 2 template commonly used in the selective epitaxial growth process have, however, resulted in formation of a nonsuperconducting YBCO top layer. Experiments including interfacial X-ray absorption spectroscopy for determining the possible interactions occurring at the YBCO and TiO 2 interface are reported.