Seeded Solid-Phase Epitaxy of Atomic Layer Deposited Aluminum Oxide

Abstract

We report the intentional seeding and crystallization of atomic layer deposited (ALD) aluminum oxide thin films. By decorating amorphous films with sapphire seeds and annealing to temperatures in the range of 950–1050 °C, lateral crystallization within the film plane resulted in monocrystalline regions up to several micrometers in width. Electron backscatter diffraction measurements indicated that the crystallized regions were α-Al2O3. The shape of the crystallized domains was correlated with crystal orientation, reflecting the anisotropic growth rates of α-Al2O3, in which the basal plane growth directions were found to have the largest growth rates. Lateral growth rates were not constant and decayed to near zero after 8 and 40 h for samples annealed at 950 and 1050 °C, respectively, which was attributed to solid-state reaction with the SiO2 substrate or other changes in the amorphous regions. We also demonstrate that a large fraction of the film area can be crystallized using a dense array of seed crysta...