Structural and electronic properties of metastable epitaxialFeSi1+xfilms on Si(111)

We have investigated the epitaxial growth and the electronic properties of a metallic metastable FeSi phase crystallizing with the CsCl structure on Si(111). Upon annealing below 500 °C the stoichiometry of thin films (<20 Å) evolves towards ${\mathrm{FeSi}}_2$ with no change of symmetry, i.e., the defect CsCl structure with a statistical occupation of metal sites remains epitaxially stable for all ${\mathrm{FeSi}}_{1+\mathit{x}}$ (0≤x≤1). Films thicker than -20 Å exhibit a transition to the cubic ε-FeSi phase. The electronic band structure of FeSi (CsCl) has been calculated self-consistently using the full-potential linear augmented–plane-wave method.