On the development of long‐range order in ultra‐thin amorphous Al ₂ O ₃ films upon their transformation into crystalline γ‐Al ₂ O ₃

Abstract

Abstract The changes in the local chemical environments of Al and O ions in ultra‐thin (<1 nm) amorphous Al 2 O 3 films on Al{111} and Al{100} substrates during their transformation into γ‐like‐Al 2 O 3 have been deduced from the corresponding changes in the so‐called Auger parameters for Al and O (as measured using XPS), in combination with structural analysis by high resolution transmission electron microscopy and low‐energy electron diffraction. It is demonstrated that the difference between the O and Al Auger parameters can be employed to monitor the change in polarisation state of the O anions in the oxide film during the amorphous‐to‐crystalline transition. It follows that ( i ) the amorphous‐to‐crystalline transition occurs at higher temperatures (starting at T > 425 K) for the oxide films grown on Al{111} than for the oxide films formed on Al{100} (starting at T < 400 K) and ( ii ) the low‐mismatch (epitaxial) crystalline oxide films on Al{111} possess a higher degree of crystalline order as compared to the high‐mismatch oxide films formed on Al{100}. Copyright © 2008 John Wiley & Sons, Ltd.