Localized and Delocalized Features of Microscopic Work Functions

Recent measurements of the microscopic work function distributions based on the local tunneling barrier height by means of scanning tunneling microscopy have been reviewed. Highly localized and widely delocalized features of the microscopic work function have been observed. As a former case, individual atoms on NiAl(HO) show element-specific local work functions. On the other hand, the effect of work function reduction by Cs adsorption on Pt(111) extends over an area wider than tens of nanometers. These results indicate that the work function distribution can not be explained within the framework of electric dipole moments induced by surface atoms, and that detailed features of wave functions should be taken into account