Characteristics of YBa2Cu3O7 thin films deposited on substrates buffered by various TiO2 layers

Abstract

Titanium nitride (TiN) and superconducting YBa2Cu3O7 (YBCO) thin films have been deposited sequentially on SrTiO3(STO)(100) substrates by in situ pulsed laser ablation. The TiN films were originally intended to serve as the lower contact electrode of the c-axis YBCO thin films. It was found that, although high-quality YBCO films could be obtained with the YBCO/TiN/STO(100) bilayer structure, the TiN(100) layer was oxidized which changed the structure into YBCO/TiO2/STO(100) during YBCO deposition. Comparative studies of depositing YBCO films directly onto a dc-sputtered TiO2/STO(100) template conventionally used in the selective epitaxial growth (SEG) process have, however, resulted in formation of a nonsuperconducting YBCO top layer. The characteristics of the resultant TiO2 layers obtained using various processes were analyzed to delineate the apparent discrepancies.