Vacancy charging on Si(1 1 1)-“1 × 1” investigated by density functional theory

The structure and energetics of charged vacancies on Si(1 1 1)-“1 × 1” are investigated using density functional theory calculations supplemented by estimates of ionization entropy. The calculations predict multiple possible charge states for surface vacancy. The neutral state of the vacancy dominates up to 1200 K, but the −1 state dominates above this temperature on real Si(1 1 1) surfaces for which the Fermi level lies near the middle of the band gap.