Ion-beam mixing at the Fe/Al2O3interface as revealed by conversion-electron Mössbauer spectroscopy

The effects of ion-beam-induced atomic mixing and subsequent thermal treatments on the single-interface Fe/${\mathrm{Al}}_2$ ${\mathrm{O}}_3$ structure are investigated by use of the techniques of conversion-electron Mössbauer spectroscopy, small-angle x-ray diffraction, and resistivity measurements. On the basis of the average values of hyperfine-interaction parameters and also their distributions it is concluded that the as-mixed state of the interface consists of the ${\mathrm{FeAl}}_2$ ${\mathrm{O}}_4$ phase along with nonstoichiometric FeO. Upon annealing at 600?deC the mixed state leads to precipitation of α-Fe with a reduced contribution of ${\mathrm{FeAl}}_2$ ${\mathrm{O}}_4$, via gradual transformations at lower annealing temperatures of 300?deC and 450?deC. These features are distinctly different as compared with the case of the thermally induced transformations in the as-deposited sandwich structure, which do not show formation of the ${\mathrm{FeAl}}_2$ ${\mathrm{O}}_4$ phase. The dependence of the mixing reaction on the ion dose has also been investigated. Preliminary Mössbauer data on the influence of a pulsed ruby laser beam (694.3 nm) on the Fe/${\mathrm{Al}}_2$ ${\mathrm{O}}_3$ interface are also presented and compared with the data on ion-beam mixing.