Amorphous-like nanocrystalline γ-Al₂O₃ films prepared by MOCVD

Alumina (Al₂O₃) films were prepared by metalorganic chemical vapor deposition using aluminum tri-acetylacetonate as a precursor. The effects of deposition conditions on film phase, microstructure, and deposition rate were investigated. γ-Al₂O₃ films were obtained at substrate temperatures ranging between 1173 and 1373 K and total chamber pressures ranging between 400 and 1000 Pa, whereas α-Al₂O₃ films incorporating a small amount of the γ phase were obtained at 1373 K and 800 Pa. Al₂O₃ films prepared at 1173 K showed a halo in X-ray diffraction patterns, consistent with amorphous structures. However, TEM observations suggested that these films consisted of a nanocrystalline γ-Al₂O₃ phase containing trace amounts of carbon.