Surface-bulk core-level binding-energy shifts for Al(100).

Abstract

The mechanisms responsible for the core-level binding-energy (BE) shifts that occur for surface and bulk atoms of the Al(100) surface are identified and characterized through theoretical analyses of the surface electronic structure. Two initial-state mechanisms are shown to be responsible for the shifts of the surface atom BE's from bulk values; final-state effects make only very minor contributions to these shifts. We are able to directly relate the important initial-state effects to the chemical environment and the chemical bonding of atoms at the surface and in the bulk. These mechanisms affect the different levels differently and we predict that the Al surface core-level shifts will be larger in magnitude for the Al 2p level than for the 2s level. The difference predicted, \ensuremath{\sim}50--100 meV, can, in principle, be resolved by present-day high-resolution photoemission measurements.