Image formation in the field ion microscope

Abstract

Present theories of field ionization at a metal surface neglect the effect of the field on the electronic structure of the surface. The variations in the local electronic structure near an ion core give rise to field fluctuations above the surface. The ionization probability is a sharp function of field strength and fluctuations of a few per cent may be detected. The field fluctuations are themselves enhanced by changes in the electronic structure occurring near the applied field. The field ion microscope depends for its success on this enhancement and on the sensitivity of the ionization probability to local changes in field strength.