Adsorption of O2 and CO2 on the Si(111)-7 × 7 surfaces

► O2 and CO2 both dissociatively adsorb on the Si(111)-7 x 7 surfaces. ► The oxide film contains two chemisorbed oxygen species. ► Oxygen atoms adsorb at the on-top site (SiOy) and the Si-Si bridge site (SiOx). ► Thermal-induced conversion between these two oxygen species was detected.