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Formation of Very Thin Epitaxial Al2O3 Pre-layer with Very Smooth Surface on Si (111) Using a Protective Oxide Layer

We propose the formation of an Al2O3 pre-layer using a protective Si-oxide layer and an Al layer. Deposition of a thin layer of aluminum onto a Si surface covered with a thin Si-oxide layer and annealing at 800°C led to the growth of Al2O3 layers on Si (111). A very smooth and uniform Al2O3 (111) pre-layer film was epitaxially grown on a Si (111) substrate. The surface of the γ-Al2O3 film grown on the Al2O3 pre-layer was very smooth with a Z range of ∼3 nm. However, the surface grown without the Al2O3 pre-layer had numerous convex structures concerning with SiOx clusters with a Z range of ∼10 nm. Etching of the Si substrate by N2O gas could be avoided in the initial growth stage by the Al2O3 pre-layer. It was confirmed that the Al2O3 pre-layer was effective in improving the surface morphology of the very thin γ-Al2O3 films.