Metastable iron silicide phase formation by pulsed laser annealing

Abstract

Thin films of ε-FeSi were grown by deposition of Fe on a Si〈111〉 substrate under ultrahigh vacuum conditions, followed by in situ annealing at 450 °C. These ε-FeSi films were subjected to irradiation from a pulsed excimer laser in the energy density range 0.30–0.90 J/cm2, in order to study the phase formation and crystallization processes of metastable [CsCl]Fe1−xSi phases. The samples were analyzed by Rutherford backscattering and channeling spectrometry and by cross-sectional transmission electron microscopy. Considerable diffusion of silicon into the silicide film was found to occur during the pulsed laser annealing, resulting in a film with nonstochiometric composition. In contrast to solid phase reaction, epitaxial ordering in the iron silicide film is observed during pulsed laser annealing when the film’s composition approaches that of FeSi2. Analysis by cross-sectional transmission electron microscopy confirmed that the phase which exhibits epitaxial ordering corresponds to the metastable [CsCl]Fe1−xSi phase. Upon annealing at 600 °C for 1 h, this metastable phase converts into the semiconducting β-FeSi2.