Electronic mechanisms for sputtering of condensed-gas solids by energetic ions

Abstract

The sputtering of condensed gas films by ions with energies > 10 keV / amu is controlled by the electronic energy loss of the ions. The sputtering yields are large, from 0.1 to 10 3 or more molecules lost per incident ion, and they are predominately quadratically dependent on the electronic energy loss. The sputtering mechanisms that may be effective depend on the radial distribution of the initial ionization and excitation, the Coulomb energy in the separated charge distribution, the relaxation of the charge cloud to form a neutral plasma and the transfer of energy from the electronic to the nuclear system. The formation of mobile fragments in condensed molecular gas films and their activated diffusion are also features of the process. These factors that lead to loss of heavy particles from the surface of the films are considered in some detail.