The charge transfer between metal and an adsorbed atom observed by means of a scanning field emission microscope (SFEM)

This paper describes the application of a scanning field emission microscope to observe oscillations in the charge density surrounding an adsorbed impurity on a surface of a tungsten tip. It presents records of SFEM images of a selected part of the tip. The time interval between two successive scannings was ≅ 34 s. The images present fluctuations of a local field emission current which are interpreted as local variations in the electronic structure of the surface at the adsorbed molecule. These fluctuations are explained assuming the existence of the atomic-like oscillations of the local density of states which arise from the presence of the adsorbed molecule. This behavior was predicted earlier by Eigler, Weiss, Schweizer and Lang [Phys. Rev. Lett. 66 (1991) 1189].