AVS 47th International Symposium
    Surface Science Tuesday Sessions
       Session SS2-TuA

Paper SS2-TuA3
Ion-Influenced Nucleation and Surface Diffusion: A Computational Study

Tuesday, October 3, 2000, 2:40 pm, Room 209

Session: Stimulated Processes and Excitations
Presenter: Z. Wang, University of Illinois, Urbana-Champaign
Authors: Z. Wang, University of Illinois, Urbana-Champaign
E.R. Blomiley, University of Illinois, Urbana-Champaign
E.G. Seebauer, University of Illinois, Urbana-Champaign
Correspondent: Click to Email
Ion-beam assisted deposition (IBAD) has been used to improve material properties for a wide variety of semiconductors, metals and oxides. In many applications, beneficial effects derive from ion-induced surface diffusion, while deleterious effects derive from ion-induced damage to the substrate. Process optimization involves finding a kinetic balance between these opposing effects, which in turn demands useful rate expressions. We have recently demonstrated experimentally both the enhancement and inhibition of surface diffusion by low-energy ions in the case of Ge/Si(111). We have simulated this system via molecular dynamics, and have developed a fairly nuanced picture of the interplay between sputtering, knockin, and vacancy formation on the surface and within the bulk. Our simulations show marked thresholds for both ion energy and substrate temperature, with a previously unknown conservation law relating these two parameters: E + bT = constant. The physical significance of the proportionality constant b we derive is discussed. The ideas deriving from these simulations are then applied to continuum simulations of ion-influenced nucleation during IBAD, with the goal of explaining why ions sometimes increase nucleation densities and other times decrease them.