ABSTRACT
Ionisation of the surface atoms of a solid by bombardment with charged particles is an important field of study from the viewpoint of the fundamental physics it invokes. The subject has also several aspects of relevance to ion-beam methods and to surface analytical physics generally. Bombardment of solids with ions of energies typically used in Secondary Ion Mass Spectrometry (SIMS) excites secondary electrons and this ‘ion-induced’ electron emission is employed in a modern SIMS instrument to provide an ‘SEM’ image of the surface analysed. The yield of sputtered ions from a solid, produced by ion-impact, is determined by factors that include sputter rate, surface composition and probability of ionisation of a given species. The dramatic dependence of the relative intensities of atomic-like peaks, to the background silicon valence-band Auger emission, is consistent with the interpretation that these peaks arise from excited ions and neutrals outside the solid.
