Local Mixing Model with Sputtering/Redeposition and Projectile-Implanted Atom Interaction

摘要

A previously discussed local mixing model (LMM) accurately describes the buildup of implanted hydrogen to saturation concentration and subsequent isotope exchange for implantation into a variety of materials of interest to the fusion community. Sputtering and surface deposition were not initially included in this model. We have now incorporated into the LMM the effects of sputtering and target-atom redeposition and have also included (in an approximate fashion) the slowing and scattering of implanted ions by previously implanted impurity species. This latter effect has important consequences for high fluence implants. Equations are derived which govern the evolution of the depth profiles of the implanted species and a formal solution is given for conditions which often are encountered in laboratory experiments. The time (fluence) dependence of the depth profile is discussed, and numerical results are compared with experiment for oxygen implantation into graphite at energies for which surface erosion is a significant effect. Solutions to the equations are also discussed for cases in which surface redeposition is significant. These latter solutions are pertinent to impurity and hydrogen isotope buildup in first wall components in operating fusion reactors. (ERA citation 11:033410)