X-ray-diffraction mapping of epitaxial ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{7\mathrm{-}\mathit{x}}$ thin films: Determination of in-plane epitaxy and a-, b-, and c-axis lengths in films with varying oxygen deficiency

Epitaxial ${\mathrm{YBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{7\mathrm{-}\mathit{x}}$ thin films with varying oxygen content have been studied by x-ray-diffraction (XRD) mapping. Results show that the films have a high epitaxial quality with the a and b axes aligned in the [100] or [010] directions of the (001) ${\mathrm{LaAlO}}_3$ substrate. The two twin domains in the orthorhombic films are present in equal amounts, both for the as-deposited and the oxygen-deficient films. From XRD maps of the (00l), (308), and (038) peaks, the a-, b-, and c-axis lengths were measured as a function of superconducting transition temperature ${\mathit{T}}_{\mathit{c}}$. The results show that the unit-cell variation for relaxed epitaxial films agrees with that of bulk material.