Influence of surface morphology on the Si(100) and (111) ionization potentials - art. no. 195305

Using an ab initio pseudopotential approach, we have investigated the depen dence of the Si ionization potential on surface atomic relaxation, reconstr uction, and crystallographic orientation. Surface reconstruction and relaxa tion tend to decrease the Si (100) and (111) ionization potentials. The Si( 100) ionization potential, however, is systematically larger than the Si(ll l) potential for all surface geometries examined, i.e., bulk-truncated, rel axed, and (2 x 1) reconstructed configurations. Such a trend is at variance with the behavior of most metals, whose ionization potential increases wit h increasing surface atomic packing (Smoluchowski's rule). Based on an atom ic-scale analysis of the surface electronic charge, we explain this reverse d trend, and relate it to an anomaly previously observed in the Al ionizati on potential and attributed to the open p-shell nature of this element.