Epitaxial films of YBa2Cu3O7−δ on NdGaO3, LaGaO3, and SrTiO3 substrates deposited by laser ablation

Abstract

Frequency‐doubled Nd:YAG laser (532 nm) pulses of 1.7 J/cm² and 10 ns duration were used to deposit thin films of YBa₂ Cu₃ O_7−δ by laser ablation on NdGaO₃ , LaGaO₃, and SrTiO₃ substrates held at 725±5 °C in 0.2 Torr of O₂ ambient. Electrical resistivities versus temperature of all films show normal metallic behavior and sharp superconducting transitions with T_c (R=0) at 92–93 K. Critical current densities in 0.3–0.6 μm thick, 200 μm long, and 10–30 μm wide strips were measured to be 10⁶ A/cm² at 60, 77, and 80 K in the films on LaGaO₃, NdGaO₃, and SrTiO₃, respectively. X‐ray diffraction patterns show that all films grew epitaxially, with domains of only two crystalline orientations rotated 90° with respect to each other in the a‐b plane (consistent with twins), and the c axis perpendicular to the substrates. The closely matched lattice constants of the film and substrates (0.8–2.1%) result in epitaxial growth of the films.