Towards a universal model for sputtered ion emission

Experiments are described in which the positive and negative relative ionization probabilities are measured for fourteen elements and two compound semiconductors, sputtered with either oxygen or cesium primary ions. By measuring the relative ionization probabilities of three dopant elements, ion-implanted simultaneously in all samples to the same common dose, a matrix-effect factor was determined for each sample. It is shown that, when the substrate ion yields are corrected for their respective self-matrix effects, the positive ion yields, and, to some extent the negative ion yields, scale exponentially with ionization potential or electron affinity. The extent to which such exponential ion yield behavior is a universal feature of sputtered ion emission is examined, and it is shown that, not only must a universal model of sputtered ion emission rationalize such behavior, but also the detailed nature of the exponential ion yield data closely constrains the nature of such a model. In particular, it is shown that the ion yield data contains no evidence for nearest neighbor effects or band structure effects in sputtered ion emission.