Sputtering of a Solid with Ion Beams

Abstract

We have already noted that beams of ions or neutral atoms striking a solid surface engender collisions between the incident particles and target atoms accompanied by the scattering and penetration of the incident particles and the emission of electrons. At the same time, some of the energy and momentum is transferred to the target atoms, and as a result of this the atoms may leave the target in the form of atoms, ions, or molecules [1]. This phenomenon, taking place in parallel with the scattering of the primary particles, was originally observed on the cathodes of ionic devices and was accordingly called cathodic (or cathode) sputtering. In the presence of adsorbed particles on the target surface (arising from the primary ions and residual-gas atoms), these may also be subject to sputtering. As a result of this, in addition to neutral atoms sputtered from the film, the secondary ions may include positive and negative ions arising as a result of film sputtering; these are quite indistinguishable from the rest. Thus, the phenomena of the scattering of primary ions and cathodic sputtering are closely related and sometimes experimentally indistinguishable. In view of this these phenomena cannot be considered in isolation, either theoretically or experimentally, although, until now, in view of experimental difficulties, secondary emission and cathodic sputtering have been considered separately.