Sputtered and Reactively Grown Epitaxial GdAIO3Films as Buffer Layers for C-Oriented YBa2Cu3O7-δFilms on R-Sapphire

Abstract

AbstractThin films of the orthorhombic perovskite GdAlO3were grown on R-plane sapphire single crystals. Two different film growth methods were used,viz.(i) a chemical reaction of a Gd-O plasma with the sapphire crystals, and (ii) the reactive radio frequency (r.f.) sputtering of a GdAlO3target. Subsequently, YBa2Cu3O7-δ(YBCO) films were deposited onto the GdAlO3buffer by pulsed laser deposition (PLD). The GdAlO3and YBCO films were investigated by Xray diffraction pole figure analysis and transmission electron microscopy (TEM), including highresolution transmission electron microscopy of cross sections. Independent of the deposition method the GdAlO3films grew according to the nearly equivalent orientation relationshipsThe GdAlO3grains are additionally tilted by angles up to ± 3° around the sapphire [11.1] axis. On top of these buffer layers the YBCO films grew with c-orientation and with an in-plane rotation of 45°. YBCO films of 200 nm thickness on GdAlO3buffer layers with a thickness of 10 to 20 nm showed a Tc> 87 K and a jc(77 K) > 3×106A/cm2.