Resolution of the Atomic Structure of a Metal Surface by the Field Ion Microscope

Abstract

A formula for the resolution of the field ion microscope is derived by considering that most of the ions originate from rebounding molecules after random elastic collision with the surface. Cooling the tip with solid N₂ or liquid H₂ in order to obtain a large accommodation coefficient drastically reduces the lateral velocity of the ions in a helium operated microscope. As a result the potential resolution for a tip of radius 1000 A is improved to 1.5 A. Photographs show the individual atoms of a tungsten surface. The actual resolution is sufficient to resolve neighboring atoms with 2.74 A separation.