Thickness Dependent Formation of Iron Silicides on Clean and Boron Modified Si(001) Surface

Abstract

Comparative study of solid phase epitaxy (SPE) of iron silicides on Si(001)2×1 and boron modified Si(001)4×4-B was conducted for iron coverage, which was varied from 0.6 to 11.3 monolayers (MLs). It was found that annealing of Fe film at 800 • C leads to formation of islands of iron silicide, whose type depends on the Fe film thickness. Using reflection high energy electron diffraction method (RHEED) and atomic force microscopy (AFM), it was shown that at Fe coverage of less than 1 ML the growth of ε-FeSi and α-FeSi2 islands occurs on Si(001)2×1 surface. Increase of Fe coverage up to ∼3 ML results in growth of three dimensional (3D) γ-FeSi2 islands, preferentially, as well as 2D islands of β-FeSi2. For iron film with thickness of 4-4.6 ML the complete transition to growth of β-FeSi2 islands was observed. It was found that in the case of the Si(001)4×4-B surface preferable growth of 3D γ-FeSi2 islands occurs starting from the coverage of 0.6 ML, while the transition to growth of β-FeSi2 islands takes place at Fe coverage of ∼6.3 ML.