Comparative Studies on Oxygen Diffusion Coefficients for Amorphous and γ-Al₂O₃Films using¹⁸O Isotope

Abstract

We systematically investigated the oxygen diffusion in both amorphous and γ-Al2O3 films using 18O as a tracer and observing depth profiles by secondary ion mass spectroscopy. The oxygen diffusion coefficients for amorphous Al2O3 films were two or three orders of magnitude larger than those of the γ-Al2O3 films. The activation energies of about 1.2 eV for both films were considerably lower than those for bulk α-Al2O3. These results could be explained by the difference in Al2O3 structure: α-Al2O3 has a dense corundum structure while γ-Al2O3 has a defective spinel structure with cation site vacancies. We found that the amorphous Al2O3 films prepared by atomic layer deposition could function as a barrier layer against oxygen diffusion only within a limited range of heat treatment conditions.