Substrate using epitaxial Al_2O_3 film for hetero-epitaxial growth and device applications

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We proposed the use of an epitaxial γ-Al_2O_3 film as a buffer layer to form epitaxial PZT thin file and, epitaxial Pt films on Si substrates. The epitaxial γ-Al_2O_3 films were grown on a Si substrate using chemical vapor deposition (CVD) and their applications have been reported γ-Al_2O_3 is spinel structure as is MgO. The lattice mismatch between γ-Al_2O_3 and Pt is smaller than that between MgO and Pt. This suggests a possibility of growing epitaxial Pt films on γ-Al_2O_3. We report the first successful formation of epitaxial Pt films and PZT film on Si substrates by using an epitaxial γ-Al_2O_3 buffer layer. Epitaxial Pt films were successfully RF sputtered on Si substrates using an epitaxial γ-Al_2O_3 buffer layer. The Crystallinity of the Pt films was strongly affected by deposition temperature. XRD and RHEED patterns indicated that an epitaxial Pt film was grown on the γ-Al_2O_3/Si substrate. Epitaxial Pt on γ-Al_2O_3/Si substrates could provide a possible way to improve the performance of a device whose properties depend on the orientation of a ferroelectric film.