Theoretical calculation of core level shifts for [formula omitted] surfaces

Abstract

Si 2p and O 1s peaks in X-ray photoemission spectroscopy (XPS) spectra from initial oxidized Si surfaces were systematically studied using O Si(111) 2 × 2 adatom-restatom models with the non-empirical self-consistent band method. The calculations sho that 2p levels of Si atoms with an intermediate number of bonding O atoms appear at intermediate positions with about 1 eV spacing, which supports the validity of the peak assignments widely used in the experimental analysis. However, 2p levels of Si atoms with a dangling bond are found to be exceptions where the traditional assignment does not hold. For O 1s levels, the assignment widely used in the experimental analysis cannot be justified. These breakdowns of assignments can be explained by the variety of the bonding configurations on the surface. O 1s peaks are found to be more sensitive to the bonding structure than Si 2p peaks, which suggests that they are more useful in rigorously determining the structure.