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.