Structural and optical analysis ofβ−FeSi2thin layers prepared by ion-beam synthesis and solid-state reaction

The $\ensuremath{\beta}\ensuremath{-}{\mathrm{FeSi}}_{2}$ phase was fabricated using two different techniques: ion-beam synthesis and solid-state reaction of a thin Fe layer with Si substrate. The crystal structure of the films was investigated by grazing incident asymmetric x-ray diffraction. The generalized matrix method was used to obtain the dispersions of the absorption coefficient $\ensuremath{\alpha}(E)$ and of the refractive index $n(E)$ from the experimental transmittance and reflectance spectra, accounting for the surface and interface roughness. From $\ensuremath{\alpha}(E)$ and $n(E)$ dependences a direct band-gap energy, ${E}_{g}=0.80$ eV was determined. When interpreting quantitatively the $\ensuremath{\alpha}(E)$ dependences, the Burstein-Moss effect was considered.