Ab-initio theory of initial oxidation of silicon (001) surfaces

摘要

The oxidation of the Si(001) surface is an important process on both technological and theoretical grounds. Experimental studies have not provided a clear picture of even the relevant atomic structures during the initial stages of oxidation, while previous theoretical studies of these processes have yielded contradictory results. Using careful first principles total-energy calculations based on density functional theory, we study several mechanisms of incorporating a sub-monolayer coverage of oxygen into the characteristic p(2 x 1) dimer reconstruction of the Si(001) surface. Our recently developed Adaptive Coordinate Real-space Electronic Structure (ACRES) method allows us to obtain results that are adequately converged with respect to the numerous computational parameters associated with this difficult system. We compare our results with previous theoretical work and propose a physically motivated two step pathway for the initial incorporation fo an oxygen atom into the dimerized surface. Based on our results, we can explain what formerly appeared to be puzzling Ultraviolet Photoelectron Spectroscopy measurements which indicated that each initial oxygen atom saturates two surface dangling bonds.