Secondary ion production by electron and ion bombardment of alkali halides

Abstract

We have investigated desorption of positive and negative ions for electron and ion bombarded NaCl single crystals. Our experiments include the first systematic measurements of electron-stimulated desorption of negative ions from an electron irradiated (100) surface of NaCl. Measurements of the mass distributions and relative yields of emitted particles indicate that during electron bombardment, positive ions are formed by gas-phase ionization of neutral atoms and molecules by primary and secondary electrons. In contrast, electron desorbed negative ions are created by direct emission of Cl − from the surface due to electronic processes. A mechanism of ion formation during keV, heavy ion bombardment is discussed in terms of an Auger process and/or direct emission of lattice ions from a collision cascade.