Bonding Configurations and Observed XPS Features at the Hydrogen Terminated (100) Si Surface: What Can We Gain from Computational Chemistry

摘要

Density functional (DFT) calculations for different size cluster models of the hydrogen-terminated HF_(aq)-etched (100) Si surface have been performed to verify that the quantities of interest (namely, atomic net charges and interatomic distances) in assigning the lines observed by X-ray photoelectron spectroscopy (XPS) vary weakly with cluster size. Net charge analysis based on Voronoi Deformation Density (VDD) method and accurate DFT geometry optimization calculations involving the smallest clusters as local models of various surface silicon atoms are used to assign chemical species to the features observed in the XPS spectra through evaluation of the chemical shifts, which are controlled by both the net chaxge and the Madelung potential truncated to nearest neighbours of the considered atoms.