Rutherford backscattering and channeling studies of Al and Mg diffusion in iron oxide thin films

Thin films of $α-Fe2O3(0001)$ (hematite) and $γ-Fe2O3 (001)$ (maghemite) were epitaxially grown on $Al2O3(0001)$ and MgO(001) substrates, respectively, using the new molecular beam epitaxy (MBE) system at the Environmental Molecular Sciences Laboratory (EMSL). We have investigated the crystalline quality of these films using Rutherford Backscattering (RBS) and channeling experiments. Minimum yields obtained from aligned and random spectra are $2.7±0.3%$ for the $α-Fe2O3(0001)$ film and $14.5±0.6%$ for the $γ-Fe2O3 (001)$ film. Al and Mg outdiffusion into the hematite and maghemite films were observed at higher temperatures. Indiffusion of Fe atoms from the film into the substrate was observed for the $γ-Fe2O3(001)/MgO(001)$ system. In contrast, no Fe indiffusion was observed for the sapphire substrate.