The structure and energetics of charged vacancies on Si(111)-(7x7) were investigated by using density functional theory calculations supplemented by estimates of ionization entropy. The calculations predicted multiple possible charge states for the unfaulted edge vacancy in the adatom layer, although the -2 state was most stable on real Si(111) surfaces for which the Fermi level lay near to the middle of the band gap.

Vacancy Charging on Si(111)-(7x7) Investigated by Density Functional Theory. K.Dev, E.G.Seebauer: Surface Science, 2003, 538[3], L495-9