HRTEM characterization of YBa2Cu3O7-δ thick films on LaAlO3 substrates

High-quality superconducting YBa2Cu3O7-δ (YBCO) thick films with thickness over 2 μm were grown on LaAlO3 (LAO) substrates by photo-assisted metalorganic chemical vapor deposition (PhA-MOCVD) with a single liquid precursor delivery system. The YBCO thick films fabricated are single-crystal like with no visible grain boundaries or voids. Surface and interface microstructures of YBCO thick films have been systematically investigated by scanning electron microscopy, high-resolution transmission electron microscopy, and selected area electron diffraction. Large precipitates were observed on the surface of these films. These precipitates are mostly composed of crystalline BaCu3O4, along with some polycrystalline and amorphous YBCO phases, and were found to exist only on top of the YBCO films, with no penetration into the films. The high quality of the prepared YBCO thick films was confirmed further by the results of X-ray diffraction and Tc/Jc measurements. Thus, these thick YBCO films prepared by PhA-MOCVD have promising application potential in fields such as coated conductors