Epitaxial cubic iron silicide formation on Si(111)

Abstract

Ultra-thin (3–10 monolayers (ML)) Fe films deposited on Si(111)7×7 surfaces were annealed in the 300–600°C temperature range and investigated by X-ray photoelectron diffraction (XPD), angle-resolved ultraviolet photoelectron spectroscopy (ARUPS) and low-energy electron diffraction (LEED). ARUPS spectra reveal the formation of an iron-silicide film showing an increasing Si content with increasing annealing temperature. The comparison of the XPD results of these silicides to those of epitaxial CoSi 2 films and to the results of single-scattering calculations allows us to identify the formation of Fe silicides with a local cubic Fe environment. The orientation of the silicides with respect to the substrate is essentially of B-type. Thin-enough films (< 7 ML Fe) do not show a phase transition to β-FeSi 2 prior to disruption at about 600°C while thicker films ( ∼10 ML Fe) can transform from the metastable cubic silicide to the stable β-FeSi 2 phase at 550°C.