Atom Ejection Mechanisms and Models

Abstract

In a series of publications the authors have been exploring atom ejection from clean and chemically reacted copper and nickel surfaces under argon ion bombardment at 600 eV ion energy by classical trajectory simulations. The calculations generate a variety of experimental observables including relative sputtering yields, energy and angular distributions for the ejected atoms, multimer yields and surface damage information. The method provides a necessary first step in the development of rigorous ejection models, prior to the inclusion of ionization effects. A general conclusion from all of the calculations is that surface morphology — the location of specific atoms with respect to each other — effectively controls the ejection mechanisms for a specific system. A comprehensive comparison between the predictions of the simulations and experimental SIMS results obtained from clean and reacted surfaces has been published [1]. These comparisons are most successful when ratios of variables between different crystal faces or adsorbates in different coverages are used. Computed yields are sensitive to the crystal structure, coverage, binding energy and site symmetry of adsorbates. A recent investigation was concerned with the Cu(lll)/Ar⁺ system as a function of the ion energy [2]. This report summarizes and extends that work.