The π-bonded chain-model for Si(111)-(2 × 1) in view of recent wavevector-resolved electron energy loss spectra

Abstract

Transition energies between the occupied and empty dangling bond surface state bands of cleaved Si(111)-(2 × 1) surfaces are measured by means of high resolution electron energy loss spectroscopy. The wavevector transfer q ∥ is parallel to the Γ-J and J'-K' lines of the surface Brillouin zone. Near the energy gaps relatively large dispersion of the bands is found. This is in contradiction to band structure calculations for the buckling model but supports the recently suggested π-bonded chain model for the (2 × 1) reconstruction.