Recently solid phase epitaxial YBa2Cu3O 7-δ films such as metal organic deposition using trifluoroacetate (TFA-MOD) technique, chemical solution-based coating pyrolysis, and BaF2 ex situ post reaction process have been improving their crystalline quality. In order to grow thick films, larger thermal expansion coefficient substrates than that of YBCO are preferable. From the viewpoint of thermal expansion coefficient, MgO is a promising substrate. However, it is difficult for solid phase epitaxial YBa2Cu3O 7-δ films to grow directly on the MgO substrate, because fluorine reacts with Mg in the substrate. Therefore we evaluate buffer layer materials to protect MgO substrates against fluorine. Buffer layer are grown by pulsed laser deposition at around 730 °C on polished MgO substrates. Thin CeO2 buffer layers are difficult to grow directly on the MgO substrates. However, CeO2-capped double buffer layers grow epitaxially on MgO substrates. The examined materials for double buffer layers are CeO2/SrSnO3, CeO2/BaSnO3 and CeO2/BaZrO3. Crystallinity of the buffer layers are characterized by X-ray diffraction (XRD) θ-2θ-scans and XRD φ-scans. From XRD θ-2θ-scans patterns crystallinity of the CeO2 on BaSnO3 is higher than those of the others. From XRD φ-scans patterns, all of these buffer layers were the perfect in-plane alignment. The intensity of CeO2 film on BaSnO3 was the highest in all films. Surface morphologies are observed by AFM. From AFM observation, it was demonstrated that the surface of CeO2 film on BaSnO3 was smooth. We confirmed that CeO2 film grown on a BaSnO3 buffer layer crystallized better than others.
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