YBa2Cu3O x superconducting thin films prepared by low temperature vacuum codeposition

Y-Ba-Cu-O films were prepared by low temperature codeposition of three components. The Y and Cu contents were evaporated from metallic sources, while Ba was vacuum-evaporated from Ba, BaO and BaF₂ sources in separate codeposition experiments. The lowest temperature at which superconducting YBa₂Cu₃O _x thin films (about 0.5µm thick) preparedin situ was near 500°C. This process enables preparation of superconducting films on various substrates (SrTiO₃, MgO, Al₂O₃, Si) without a buffer layer. Zero-resistance critical temperature was as high as 88 K and the critical current density was 10⁴ A/cm² at 4.2 K. The morphology of the films was granular with disordered grain orientation, the average grain size being typically 0.5µm.