Monte-Carlo calculation of low energy ion collection in the presence of sputtering, range shortening, knock-on and diffusion

Monte-Carlo calculations of ion collection show that the “range shortening” effect due to previously collected atoms is nearly cancelled by the knock-on effect of the bombarding ions at moderate fluences (maximum concentration < 10 at.%). At saturation collection the effects are more noticeable, e.g. in the 74 keV Xe implantation in Si, the range profile is moved towards the surface, the total amount of Xe is smaller by 25% and a maximum appears in the collection curve, if these effects are taken into account. The greater part of the differences between theory and experiment is assumed to be due to diffusion. A simple and efficient Monte-Carlo method is proposed to treat diffusion and changes in the target during ion collection. Discrepancies between the theory and recent range measurements of aluminium in several metals can be explained by diffusion combined with trapping.