A systematic investigation was made of O diffusion in amorphous and γ-Al2O3 films by using 18O as a tracer and by observing depth profiles by using secondary ion mass spectroscopy. The O diffusion coefficients for amorphous Al2O3 films were 2 or 3 orders of magnitude larger than those of the γ-Al2O3 films. The activation energies of about 1.2eV for both films were considerably lower than those for bulk α-Al2O3. The results could be explained by the difference in Al2O3 structure. That is, α-Al2O3 had a dense corundum structure, while γ-Al2O3 had a defective spinel structure with cation site vacancies. It was found that the amorphous Al2O3 films prepared by atomic layer deposition could function as a barrier layer to O diffusion only within a limited range of heat-treatment conditions.

Comparative Studies of Oxygen Diffusion Coefficients for Amorphous and γ-Al2O3 Films using 18O Isotope. T.Nabatame, T.Yasuda, M.Nishizawa, M.Ikeda, T.Horikawa, A.Toriumi: Japanese Journal of Applied Physics-1, 2003, 42[12], 7205-8