STM studies of the interaction of surface state electrons on metals with steps and adsorbates

Scanning tunneling microscopy (STM) studies have shown that scattering of surface state electrons by steps and adsorbates leads to long-range oscillations in the local density-of-states (LDOS). Here we examine the nature of the states probed in the vicinity of the scatterer. We find that at steps, the LDOS primarily reflects the Smoluchowski charge-redistribution process. Perturbation of the surface state by the step extends more than 10 إ from the step-edge and induces bulk-surface state mixing. Unusually narrow spectra and delocalized images are observed for adsorbed sulfur on Ag(111) and are explained in terms of the electronic structure changes induced by chemisorption.