Adsorption of atomic and molecular oxygen and desorption of silicon monoxide on Si(111) surfaces

Quantum chemical theoretical calculations were performed to investigate the adsorption reaction of an ${\mathrm{O}}_2$ molecule or an O atom with a single dangling bond on the Si(111) surface and the desorption reaction of SiO gas from the O-adsorbed Si surface. The dissociative reaction of an ${\mathrm{O}}_2$ molecule requires an activation energy of $58\hspace{0.5em}\mathrm{k}\mathrm{c}\mathrm{a}\mathrm{l}/\mathrm{m}\mathrm{o}\mathrm{l},$ whereas no potential-energy barrier exists in the reaction of an O atom. The most stable O-adsorbed species has a Si-O-Si bridging configuration. This configuration is formed by a conversion from the preceding metastable species where an O atom directly attaches to a surface dangling bond. It was revealed in the SiO desorption that the dissociation of two Si-Si bonds and one Si-O bond was responsible for the SiO generation. The activation energy of each dissociation was estimated to be $89$ and $44\hspace{0.5em}\mathrm{k}\mathrm{c}\mathrm{a}\mathrm{l}/\mathrm{m}\mathrm{o}\mathrm{l},$ respectively. In addition, the consistency of the theoretical calculations for the kinetics of the oxygen adsorption and subsequent SiO desorption was examined under change in the size of the computational model clusters.