YBaCuO Thin-Film Growth on Electrooptic LiNbO3 Substrate with Buffer Layer

Oxide superconducting YBaCuO thin films were grown on Y- and Z-cut LiNbO3 (LN) electrooptic crystal substrates with and without buffer layers, and their film crystallinity was closely investigated by X-ray diffraction, transmission electron microscopy, reflection high-energy electron diffraction and Auger electron spectroscopy. Due to the intensive reaction, direct deposition of films resulted in poor quality. When sputtered (111)-MgO film was introduced as a buffer layer, significant diffusion of constituent atoms was unavoidable among YBaCuO, MgO and LN. As a result, the superconductivity of the YBaCuO layer was substantially degraded. The Y2O3- stabilized ZrO2 (YSZ) grown by sputtering, followed by wet O2 anneal, served as a good buffer layer for Y1Ba2Cu3Oy films on LN substrates, and epitaxial growth of (00l)-Y1Ba2Cu3Oy with Tc0=89 K was reproducibly obtained on Y-cut LN substrates.