The role of the electronic structure in charge exchange between low energy ions and surfaces

In this study some of the fundamental aspects of neutralisation have been addressed. The validity of the three-stage approach to neutralisation which involves treating neutralisation along the approach to and departure from the surface as an Auger-like process, and the neutralisation during the collisional phase as an atomic-like process has been justified by measurements on the interaction of He⁺ with Pb. Neutralisation along the exit path is shown to be independent of the oscillatory niutralisation cross section associated with the collisional phase. In order to determine the role of the work function and valence band width in determining neutralisation rates for inert gas ions, a range of elements has been studied (Ni, Cu, Zr, Pd, Ag, Au, Pb). The role of the projectile has been assessed by the use of three inert gas ions (He⁺, Ne⁺, Ar⁺) as projectiles. This has been extended by comparison with previously reported results involving the neutralisation of Al⁺ of an Al surface and Si⁺ off a Si surface. The conclusion of this study is that there is no experimental evidence for higher neutralisation rates in situations where a resonance process is considered to be more likely than an Auger process. A linear correlation has been found between the conduction band width and v_c v₁. There is also some preliminary evidence for a universal behaviour for the variation of neutralisation rates with particle velocity, not previously reported. © 1988.