Simulation of the atomic and electronic structure of a solid Fe wetting layer on Si(001) obtained by layer-by-layer deposition

The atomic and electronic structure of the solid wetting layer (SWL) of Fe on Si (001) is studied in the process of layer – by-layer deposition of Fe-monolayer by monolayer by quantum mechanical modeling in the framework of the electron density functional theory. It is shown that Fe atoms in SWL occupy the gaps between the atomic rows along the Si(001) – 2 $\times$ 1 dimer chains, and Fe growth occurs by stratification of SWL. In this case, coverage SWL is coated with two-dimensional layers with the structure and composition, respectively, at thicknesses of: 1–2 ML – (1 $\times$ 1)-FeSi; 3 ML – ($\sqrt2\times\sqrt2$)R45$^\circ$-Fe$_3$Si; 3 ML, 4 ML and 5 ML – (1 $\times$ 1)-Si, (1 $\times$ 1)-FeSi and (2 $\times$ 1)-Fe$_2$Si; and 6–7 ML – (1 $\times$ 1)-Fe. At the same time, starting from the thickness $d$ = 2 ML, the substrate atoms change their packing to hexagonal – with packing defects. At the same time, the electronic structure of SWL ischaracterized by $(a)$ hybridization of states, $(b)$ changing the shape and position of the bands (moving them away from the Fermi level), $(c)$ filling in states at the Fermi level, and $(d)$ complete disappearance of the band gap.