Growth of epitaxial γ-Al₂O₃(111) films using an oxidized Si(111) substrate

High-quality epitaxial γ-Al₂O₃(111) films were grown on a Si(111) substrate covered with a chemically formed 2 nm SiO₂ layer using reactive ionized beam deposition. An epitaxial γ-Al₂O₃ layer was formed at above 800°C, while the films showed polycrystalline below this temperature. Al₂O₃ films grown on an oxidized Si substrate showed a better crystalline quality, a more fiat surface and a sharper interface than the films grown on a clean Si substrate. A thin SiO₂ layer acts as a barrier to prevent a direct reaction of incident Al with Si substrate, the thin layer is consumed during the Al₂O₃ growth to yield an abrupt Al₂O₃/Si interface. The role of the thin oxide layer on the film growth and the chemical reactions at the interface during the initial growth of Al₂O₃ were investigated.