Buffers for high temperature superconductor coatings. Low temperature growth of CeO₂ films by metal-organic chemical vapor deposition and their implementation as buffers

Smooth, epitaxial cerium dioxide thin films have been grown in-situ in the 450-650 °C temperature range on (001) yttria-stabilized zirconia (YSZ) substrates by metal-organic chemical vapor deposition (MOCVD) using a new fluorine-free liquid Ce precursor. As assessed by X-ray diffraction, transmission electron microscopy (TEM), and high-resolution electron microscopy (HREM), the epitaxial films exhibit a columnar microstructure with atomically abrupt film-substrate interfaces and with only minor bending of the crystal plane parallel to the substrate surface near the interface and at the column boundaries. With fixed precursor temperature and gas flow rate, the CeO₂ growth rate decreases from approximately 10 angstroms/min at 450 °C to approximately 6.5 angstroms/min at 540 °C. The root-mean-square roughness of the films also decreases from 15.5 angstroms at 450 °C to 4.3 angstroms at 540 °C. High-quality, epitaxial YBa₂C₃O_7-x films have been successfully deposited on these MOCVD-derived CeO₂ films grown at temperatures as low as 540 °C. They exhibit T_c = 86.5 K and J_c = 1.08×10⁶ A/cm² at 77.4 K.