Operation of the Field Ion Microscope with Neon

Abstract

The image quality obtained with neon as an imaging gas was studied. Neon can give stable images of non‐refractory metals because its ionization field is lower than the evaporation field of these metals. Field evaporation occurs in helium and in neon at slightly lower fields than in vacuum when the incoming nonionized gas molecules which have both thermal and dipole attraction energy collide with the surface atoms. Localized field evaporation leads to dynamic end forms of the emitter tip which are characteristic for vacuum, neon, and helium. The ion image obtained with helium containing a few percent neon has a reduced contrast and shows more details around the low‐field areas. Field evaporation in this mixed gas produces surface vacancies inside closed net planes. These effects indicate that adsorbed neon atoms act as intermediate collision partners to allow a more efficient transfer of the energy from the light helium atom to the heavy metal atom.