Surface influences on resonant ionization during sputtering

Abstract

The surface motion in resonant charge exchange processes, between a sputtered atom and a metal, has been represented by a simple mechanism in which diatomic molecular systems, formed transiently, in the collision cascade, generated by the primary bombardment, between secondary emitted and substrate atoms, may trap an electron into a localized state. An Anderson–Newns Hamiltonian, containing both the atomic and the quasi-molecular levels, interacting resonantly and independently with the conduction band of the metal, has been adopted for evaluating the final ionized fraction in the outward atomic beam. Analytical calculations, including temperatures, have been performed on an interaction dynamics evolving over two different time scales, related to the classical motion of the particles in the quasi-molecules. The velocity behavior of the ionized flux has been obtained in a very simple case and its comparison to a SIMS experiment has provided interesting arguments to identify a kinematic region of dominant surface effects with respect to the well known hopping mechanism of resonant ionization.