Electron stimulated desorption of positive and negative ions from [formula omitted] surfaces

Abstract

We have examined the role of core-hole excitations in electron stimulated desorption (ESD) of positive and negative hydrogen and oxygen ions from SiO 2 Si surfaces. Thresholds observed for positive ion emission at electron energies above 100 eV are correlated with core-level binding energies of substrate atoms and explained in terms of interatomic Auger transitions. Desorption of negative ions closely follows threshold behaviour of corresponding positive ions; it is explained in terms of a charge exchange process in which the outgoing positive ions (or neutrals) capture electrons in the surface region and desorb as negative ions.