In situ epitaxial growth of YBa2Cu3O7−x superconducting thin films on (100)BaF2 substrates has been successful by an off-axis dc planar magnetron sputtering method. The zero-resistance temperatures of these thin films are about 81–84 K with transition width of 1.5 K. The characteristics of the films were examined by x-ray diffraction, reflection high energy electron diffraction, Rutherford backscattering spectroscopy ion channeling techniques, and scanning electron microscopy. The experimental results suggest that BaF2 is a promising material as substrates or buffer layers for the epitaxial growth of high Tc superconducting thin films, especially in high frequency applications. Discussions on the heteroepitaxy of the YBCO/BaF2 system are propounded.

Perfect epitaxial growth of superconducting YBa2Cu3O7−x thin films have been achieved on (100) SrTiO3, (110) SrTiO3, and (100) ZrO2 substrates using a modified planar dc magnetron sputtering system. The films exhibit zero resistances at 87–90 K with transition widths of about 2 K. The critical current density of 1.4×106 A/cm2 at 77 K so far has been measured on the (100) SrTiO3 substrate. The epitaxial orientation of the thin films was influenced by the substrate orientation, the substrate temperature, and the oxygen partial pressure. The quality of growth and the epitaxial orientation of the films were examined by electron channeling, x-ray diffraction, and reflection high-energy electron diffraction techniques. The preferential epitaxial orientation is discussed.