Electron-Hole Shake-Up in Adsorption Systems: Halogens on Semiconductor Surfaces

Abstract

In order to account for strong correlation effects, we have carried out a many body calculation of the electronic structure of the Cl/Si(100)-(2 × 1) system. The one-electron Green function is found directly from its Lehmann representation in terms of N - 1 and N + 1 electron states. These are obtained approximately by means of an iteration scheme (the lattice-configuration approach) whereby states with an increasing number of electron-hole pairs are successively included. This approach gives in a natural way the configurational composition of all the spectral features, which allows following in detail the character of possible relaxation processes. The resulting density of states is in quantitative agreement with the photoemission spectrum and describes qualitatively the desorption data of positive and negative Cl ions. It is found that most of the above spectral features are dominated by a strong shake-up of electron-hole pairs which largely invalidates a one-electron picture. This is ultimately traced to the (probably nonlinear) substrate response to the strong disruption produced by the Cl atoms (of large electronegativity).