Microstructures of epitaxial YBa2Cu3O7-δ thick films grown by photoassisted metal-organic chemical vapor deposition

Epitaxial, high-quality YBa₂Cu₃O_7-δ (YBCO) thick films were grown by a photoassisted metal-organic chemical vapor deposition technique with a single liquid precursor delivery system, and characterized by X-ray diffraction (XRD), scanning electron microscopy, and low-high-resolution transmission electron microscopy techniques. Very dense and single-crystal-like film structure was observed in all of these YBCO thick films. Large precipitates on these thick films were identified as BaCu₃O₄, sprinkled only at surface of these YBCO thick films. YBCO thick films with high crystalline and superconductive quality were confirmed by data of XRD analyses and superconductivity measurements. At the same time, the reason why epitaxial YBCO thick films with high-quality single-crystal-like structure can be grown up to about 4.5 μm thick is illustrated from the point of view of photoactivation. It is also found that these thick films were optimally oxygenated with their superconductive properties in concern.