Low energy ion-solid interactions: Model, parameter determination, and applications.

摘要

he interactions of low energy (5-350 eV) ions with solid surfaces are studied in this dissertation. A general, phenomenological model for evaluation of the influences of ion energy on the surface is presented. This model centers on three distinct types of processes, namely penetration of the ion into subsurface layers, damage of the target surface induced by the ion, and diffusion of species formed as a consequence of ion bombardment. The first two are characterized by threshold energies. Both simple defect-mediated diffusion processes are considered. Static and dynamic forms of the model are developed. The static model is developed to determine the effects of ion energy on the quality of the surface in the absence of fluence dependence. The dynamic model is used to derive rate equations which explain the fluence-dependent behavior of a surface under conditions of low energy ion irradiation. Conditions are discussed under which the dynamic model leads to the static equation. The model is in excellent agreement with experimental evidence on both dose- and energy-dependence of the effects of low energy ion irradiation. Methods of determination of the relevant threshold energies are discussed, along with the properties of the surface which determines the value of the penetration threshold. An experimental method for determination of the threshold energy for ion induced defect production in Si is developed and used to measure that threshold at 23