Photoemission study of the surface states that pin the Fermi level at Si(100)2 × 1 surfaces

Clean Si(100) surfaces of a heavily n-doped crystal have been studied with angle-resolved photoemission. A new surface state is observed at the Fermi level, only appearing close to the Γ and J̄^' points in the 2 ×{} 1 surface Brillouin zone. Because of the localization in momentum space it is concluded that the observed states are spatially extended and not related to localized defects. The emission at the Fermi level is assigned to the dispersion minima of an unoccupied surface-state band responsible for the pinning of the Fermi level at Si(100)2 ×{} 1 surfaces.