Formation and properties of thin films of iron silicides on Si(111) Surface: Ab initio simulation

Density functional theory in the generalized gradient approximation has been used to calculate the total energy and model the atomic and electronic structures of thin FeSi films with CsCl type lattice and $\gamma$-FeSi$_2$ films with CaF$_2$ fluorite type lattice on a Si(111) surface. It is shown that, upon the adsorption of two monolayers of iron atoms on Si(111), the most energetically favorable process is the growth of a $\gamma$-FeSi$_2$ film with CaF$_2$ type structure. The electronic structure of a silicide film formed upon the adsorption of one monolayer of iron atoms exhibits features that are characteristic of both FeSi and $\gamma$-FeSi$_2$. The density of states calculated for the $\gamma$-FeSi$_2$ well agrees with the experimental photoemission spectra reported in the literature.