Abstract
We have examined the fabrication conditions of epitaxial CeO 2 films on a-plane sapphire substrates, and also examined epitaxial growth of YBa 2Cu 3O 7− δ (YBCO) films on CeO 2/ a-plane sapphire substrate. The θ/2 θ XRD analysis of these composite films revealed that grains of the CeO 2 and YBCO on CeO 2/ a-plane sapphire substrate were perpendicular to the substrate. From the φ-scan XRD measurement, we found that the four 1 0 2 φ-scan peaks of the YBCO film were observed and the peak positions were shifted by 45° compared with those of the CeO 2 films. From the peak shifts we could estimate that the angle between the [1 0 0] axis of the CeO 2 and the [1 0 0] axis of the YBCO was 45°. From temperature dependence of resistivity of the YBCO/CeO 2/ a-plane sapphire substrates, we obtained a zero-resistance temperature ( T C) of 88.6 K. We found that their crystallinity and critical temperature ( T C) were quite similar to those of YBCO film on CeO 2/ r-plane sapphire substrate. At the moment, YBCO thin films on a-plane sapphire are inferior to YBCO thin film on r-plane sapphire in terms of surface resistance.
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