Epitaxial films of YBa₂Cu₃O_7-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 O7-δ by laser ablation on NdGaO3, LaGaO 3, 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 Tc (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 10 6 A/cm2 at 60, 77, and 80 K in the films on LaGaO 3, 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.