Electronic excitations of the H : Si(001)-(2x1) monohydride surface: First-principles calculations

Abstract

We investigate electronic excitations of the H:Si(001)-(2x1) monohydride surface using first-principles approaches. Density-functional theory is used to calculate the ground-state geometry of the system. The quasiparticle band structure is calculated within the GW approximation. Taking the electron-hole interaction into account, electron-hole pair states and optical excitations are obtained from the solution of the Bethe-Salpeter equation for the electron-hole two-particle Green's function. In this work we focus, in particular, on localized excitations of the silicon-hydrogen bonds at the surface layer. These excitations give rise to an outward-directed force on the hydrogen atoms, which may well explain their optically induced desorption from the surface as observed in recent experiments. The localization of the excitation is described by an artificial confinement potential in addition to standard many-body perturbation theory.