Simple valence force field-bond energy bond order (SVFF-BEBO) model for chemisorption of Oxygen on Si(111)

Abstract

When information is available for the configuration of an adsorbate during various stages of chemisorption on an absorbent, in principle, the energetics of the adsorption process can be calculated. Oxygen adsorption on silicon (111) has been studied extensively and various configurations of the silicon-oxygen molecular complex have been proposed. A Simple Valence Force Field-Bond Energy Bond Order (SVFF-BEBO) semi-empirical model has been used to determine the energetics of the initial stages of the oxidation of the ideal silicon (111) surface. The SVFF-BEBO method allows consideration of the lattice strain energy that is involved in the localized surface bonding during the formation of the surface complex. Using the best available data we show that direct oxidation of silicon to produce a SiO 2-like surface configuration is energetically feasible, but unlikely. A large activation barrier separates this possible final chemisorbed oxide state from an easily formed peroxide-bridge structure. The results of this calculation are compared with, and are in agreement with, the most recent experimental data.