A review of compositional changes of multicomponent materials (especially biomaterials) induced by ion sputtering

Abstract

It is well known that the ion sputtering process may modify the surface chemical composition of multicomponent materials as a result of preferential sputtering. Ion bombardment leads generally to surface enrichment of the component having a lower sputtering yield. Although the sputtering yield studies are very important, they do not contribute to understanding the mechanism of the preferential sputtering. The main reason is that the sputtering yield is the phenomenological coefficient and it depends on many factors, particularly on ion energy, its angle of incidence, target atomic mass to ion mass ratio, and target surface binding energy. For multicomponent materials, the effects of component mass difference and binding energy seem to be of fundamental importance for understanding the nature of the preferential sputtering mechanism. Another interesting problem is the influence of ion mixing and diffusion on the compositional changes of multicomponent materials. The main purpose of the article is to discuss the mechanism of preferential sputtering of multicomponent materials and to present the role of such phenomena as recoil and cascade sputtering, recoil implantation, mixing, diffusion, and segregation. Another issue worthy of discussion is the practical aspect of preferential sputtering, i.e., the influence of ion sputtering on compositional changes of biological implant materials.