Spatial variations in the oxygen content of YBa₂Cu₃O_{7 - δ} epitaxially deposited on MgO as assessed using a transmission electron microscopy moiré method

Abstract

Thin films of YBa₂Cu₃O_{7 - δ} (YBCO) grown by sputter deposition on MgO(001) have been examined using transmission electron microscopy. Moiré fringes originating from interference between YBCO and MgO reflections have been used to obtain values for the degree of orthorhombic distortion of the YBCO and hence its oxygen content. It is found that the oxygen content can vary and that such variations, when seen, are related to the separation of the twin boundaries. The reliability and scope of the technique used are discussed, and the results compared with information concerning the oxygen content deduced from resistance-temperature curves for the same material.