Modification of electron density in surface states: scanning tunnelling microscopyobservation of standing waves on Pd overlayers

Abstract

Modification of electron density in the surface states of Au(111) and Cu(111)surfaces by Pd deposition is demonstrated. Using a low-temperature scanningtunnelling microscope, electronic standing wave patterns are observed on amonolayer-high Pd layer whose wavelength is longer than that of the substrates.The observation indicates an upward shift of the energy level of the surface statesand reduced electron density in the states on the overlayer. A standing wavepattern depending on magnetic field was observed around an impurity atom onthe Au(111) surface.