Preservation of substrate crystal and enhancement of YBa₂Cu₃O_7-x thin film growth using YSZ/Si₃N₄ as a buffer layer

Enhancement of high temperature superconducting YBa₂Cu₃O_7-x (YBCO) thin film growth on GaAs and preservation of the substrate crystal were succesfully realized using yttrium-stabilized ZrO₂ (YSZ)/Si₃N₄ as a buffer layer. Highly c-axis oriented YBCO thin films with a zero resistance temperature as high as 85.5 K were obtained due to the use of a sub-top buffer of YSZ. The preservation of the GaAs surface at a temperature as high as 700°C in an oxygen-rich ambient, as revealed by photoreflectance measurement on the GaAs surface after removing YBCO, YSZ, and Si₃N₄ layers, was realized owing to the use of a sub-bottom buffer of Si₃N₄. Material analysis using a combination of cross-sectional scanning electron microscopy and Auger electron spectroscopy depth profiling demonstrated quite weak interdiffusions among different regions. The electrical and structural properties of both the YBCO film and the GaAs substrate after YBCO thin film deposition are believed to be the best reported so far.