An investigation was made of the structure and energetics of charged vacancies on Si(100)-(2x1) by calculations using density functional theory. The calculations predict multiple stable charge states for all vacancy structures investigated, although the neutral state was most stable for typical Si(100) surfaces. The multiplicity of possible states lends significant support to a hypothesized mechanism for non-thermal illumination influences on surface diffusion. The calculations also showed that the +1 state of the upper dimer monovacancy was destabilized by structural relaxations, leading to negative-U properties.

Vacancy Charging on Si(100)-(2x1) - Consequences for Surface Diffusion and STM Imaging. H.Yeung H.Chan, K.Dev, E.G.Seebauer: Physical Review B, 2003, 67[3], 035311 (7pp)