Effect of illumination on the preferred oxygen initial adsorption sites ata Si(111)7x7 surface

A p-Si(111)7x7 surface was exposed to oxygen both while being illuminated w ith super-band-gap energy photons and while in the dark. The initial sticki ng probability into an adsorption mode that appears as a protrusion in scan ning tunneling microscope images doubled due to illumination with 500 mW/cm (2) 532 nm light. No changes were observed in the similar to 3:1 preference of the "faulted" over the "unfaulted" halves of the 7x7 unit cell. However , exposure to Oz under illumination removed the similar to 5:1 preference o f the "corner adatom" over the "center adatom" sites, which was observed af ter exposure in the dark.