Local electronic structure of the Si(111)-(7 × 7) surface interacting with Ag atoms

Spatially resolved scanning tunneling spectroscopy was used for the investigation of changes in electronic structure of the Si(111)-(7 × 7) surface which are induced by the presence of a silver atom, a dimer and a cluster in a half-unit cell of the surface reconstruction. Tunnel spectra were measured at room temperature at significant positions in half-unit cells. The presence of one or two Ag atoms moving quickly in a half-unit cell significantly influences only filled states in spectra, while empty states remain practically unchanged and are still dominated by silicon adatom states. Corresponding features identified in the filled states depend on the number of Ag atoms in a half-unit cell and localization of these new states reflects the dynamic behavior of the Ag atom in a half-unit cell. A cluster of silver atoms in the half cell exhibits pronounced maxima in both filled and empty states of the spectrum.