Electronic structure of Al chemisorbed on the Si (111) surface

The electronic structure of Al chemisorbed on the Si(111) surface is investigated in detail by means of self-consistent pseudopotentials. Using the Lander substitutional model, we calculate the position of the Fermi level, the work function, and the local density of states. Surface states are identified and displayed in terms of charge-density contour maps. In agreement with experiment we find that the intrinsic surface states within the band gap are removed by the metal overlayer and replaced by extrinsic metal-induced surface states. These extrinsic states pin the Fermi level. In sharp contrast with jellium-semiconductor models, we find, in agreement with experiment, extrinsic surface states 1-3 eV below the Fermi level.