Stark Effect and Scanning Tunneling Spectroscopy of the Ag(111) Surface State

Low-temperature scanning tunneling spectroscopy is used to study the Ag(111) surface state over an unprecedented range of junction resistances. The presence of the tip causes a shift of the surface state towards higher binding energies, increasingly stronger as the resistance decreases. A one-dimensional model calculation reproduces this observation and provides a connection to existing photoemission spectroscopy data. Implications of the effect on STS studies are discussed