Rutherford backscattering and channeling studies of Mg and Fe diffusion atthe interface of gamma-Fe2O3(001)/MgO(001)

We have investigated the crystalline quality of an epitaxially-grown gamma- Fe2O3(001) film on MgO(001) substrate along with Mg and Fe inter-diffusion using Rutherford backscattering spectrometry (RBS) and channeling experimen ts. The channeling effect in the film appears to be reduced compared to an ideal single crystal, with the minimum yield for Fe determined to be in the range 16-18%, Growth at a substrate temperature of 450 degrees C promotes limited Mg out-diffusion into the film. Subsequent appealing results in fur ther Mg out-diffusion, which increases in extent with increasing temperatur e. A minimum of 4 at.% Mg was detected throughout the film at temperatures below the onset of Fe in-diffusion, which was found to be 800 degrees C. Th is impurity cation concentration is comparable to the native vacancy concen tration in gamma-Fe2O3 (4.8 at.%), suggesting that Mg occupies cation vacan cy sites, as already established by Auger electron diffraction measurements for this system. The Mg concentration in the film was 8 at.%, while the as sociated Fe concentration in the substrate was 3.4 at.% after annealing at 800 degrees C. Moreover, these cation impurities were uniformly distributed throughout the film and substrate, with the fraction of substitution in bo th cases >90% at lower temperatures. Copyright (C) 1999 John Wiley & Sons, Ltd.