Study of concentration variations in the metastable [CsCl]Fe1−xSi phase

The aim of this work is to investigate phase formation in the Fe–Si system upon pulsed laser annealing of an ε-FeSi layer on Si(111). The layers have been analysed with Rutherford backscattering spectrometry (RBS) and conversion electron Mössbauer spectroscopy (CEMS). Results of RBS indicate that layers are formed with an altered Fe/Si composition. Additionally, the Fe/Si composition within one layer is not homogeneous; a composition gradient is present throughout the layer. CEMS, a nuclear technique sensitive to the local environment of the 57Fe nucleus, indicates that no stable or combinations of stable Fe-silicide phases have been formed. The CEMS spectra observed point in the direction of the metastable [CsCl]Fe1−xSi phase. However, the CEMS spectra are hard to interpret, on one hand, due to the large amount of different local environments of the Fe nucleus in this [CsCl]Fe1−xSi phase giving rise to a distribution of electric field gradients and isomer shifts, and on the other hand the influence of the concentration gradient on this distribution of electric field gradients and isomer shifts. To gain more insight in the hyperfine interaction parameters of the metastable [CsCl]Fe1−xSi phase and their dependence on concentration variation, FLAPW calculations are performed. These are necessary for the confirmation of the CEMS results.