High-quality as-grown MgB₂ thin-film fabrication at a low temperature using an in-plane-lattice near-matched epitaxial-buffer layer

An as-grown MgB₂ crystalline thin film was fabricated at a low temperature of 270°C on an in-plane-lattice near-matched TiZr buffer layer grown on a sapphire Al₂O₃ (0001) surface. The critical temperature and the superconductivity critical current density of MgB₂/TiZr/Al₂O₃ were found to be high compared with those of MgB₂/Al₂O₃. The film was characterized by using synchrotron x-ray diffraction. The epitaxial relationship in the plane was MgB₂[0110]//TiZr[0110]// sapphire [1120]. In-plane-lattice spacings, d_//^MgB₂, d_//^TiZr, and d_//^sapphire obtained were 0.268, 0.258, and 0.239 nm for the MgB₂(0110), TiZr(0110), and sapphire (1120) planes, respectively.