Superconducting YBa2Cu3O7 films grown on TiO2 buffer layers derived from various processes

Abstract

YBa2Cu3O7 (YBCO)/TiN and YBCO/TiO2 bilayer structures have been prepared on SrTiO3 (STO)(100) 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(100) layer was oxidized and transformed into rutile TiO2(110) film. On the other hand, pure anatase TiO2(001) films were prepared by PLD using a rutile TiO2(110) substrate as the target. YBCO films grown on both phases of TiO2 films show virtually the same transport properties of typical good quality singlelayer YBCO films. Comparative studies of depositing YBCO films directly onto a de-sputtered TiO2 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 TiO2 interface are reported. (C) 2001 Elsevier Science B.V. All rights reserved.