Crystalline orientation of YBa2Cu3O<i>y</i> film prepared by liquid-phase epitaxial growth on NdGaO3 substrate

Abstract

Superconducting YBa2Cu3Oy films were grown by liquid-phase epitaxy on NdGaO3(110) single-crystalline substrates by a modified top-seeded solution growth method. Two different melt compositions were used. In the case of Cu-poor melt compositions (Ba:Cu=3.0:5.0), only c-axis oriented growth was observed. However, if we used Cu-rich melt compositions (Ba:Cu=3.0:6.5), both c-axis and a-axis oriented films were obtained. In the latter case the crystalline orientations of the YBa2Cu3Oy films were dependent on the temperature of the surface of the melt. At lower temperatures, c-axis oriented films were obtained, whereas the films showed a-axis orientation at higher temperatures. The width of the temperature region over which the orientation changes is less than 3 °C, which is very narrow compared to the width observed in conventional vapor phase depositions (typically 50 °C). We propose that changes in orientation during the liquid-phase epitaxial growth is due to the unique properties of the phase diagram of the Y–Ba–Cu–O system.