Theoretical studies of metal disilicide–silicon interfaces

Abstract

General trends of the chemical bonding and electronic structure for the interfaces between Si(111) and a series of metal disilicides (${\mathrm{CaSi}}_2$, ${\mathrm{ScSi}}_2$, ${\mathrm{TiSi}}_2$, ${\mathrm{VSi}}_2$, ${\mathrm{CrSi}}_2$, ${\mathrm{MnSi}}_2$, ${\mathrm{FeSi}}_2$, ${\mathrm{CoSi}}_2$, and ${\mathrm{NiSi}}_2$) have been studied using the empirical tight-binding method and the slab model. For all the disilicides the ${\mathrm{CaF}}_2$ structure is adopted. With the increase of the atomic number Z from Ca to Ni, the occupancy of the nonbonding d state of the metal at the interface changes from empty to full. The positions of the Fermi level $E_F$ for various structures of the ${\mathrm{NiSi}}_2$/Si(111) and ${\mathrm{CoSi}}_2$/Si(111) interfaces have been compared. The 180° rotation of the orientation of the ${\mathrm{NiSi}}_2$ film with respect to the substrate does not seem to affect the position of $E_F$.