Theory of Auger line shapes in chemisorption of Cl on Si(111)

Abstract

L1L2,3V and L2,3VV Auger line shapes have been calculated for Cl and Si in the adsorption system Si(111)-Cl(1 × 1), based on an empirical tight-binding surface band-structure calculation. The fact that Cl and Si orbitals do not mix strongly means that the local densities of states (LDOS) at the Cl and Si atoms are very different; this difference is reflected in the predicted Cl and Si Auger spectra, and its experimental observation would be of considerable interest, as a demonstration that Auger spectra can provide local electronic structure information. The Si L1L2,3V spectra from clean and Cl-covered Si(111) will probably not be different enough, because of the breadth of the Si 2s level, to permit one to obtain useful information from their difference. However, if one uses a grazing incidence beam to enhance the contributions of the outermost Si layers, the differences between the Si L2,3VV spectra for the clean and covered surfaces should be quite prominent, and will reflect the changes in the Si electron energy distribution induced by the formation of strong - and weak -bonds with the Cl. The calculated Cl spectra decompose readily into contributions from the s- and p-like components of the Cl LDOS and from convolutions of them, a fact which will permit the experimental determination of Auger matrix-element angular-momentum dependence. © 1978 The American Physical Society.