The role of flux-focusing in the origin of shoulders in ion channeling angular scans

We have investigated the effect of ion channeling flux-focusing on the origin of high near-surface shoulders   in channeling angular scans of single crystals. We simulate 2 MeV He ion planar channeling in Si{100} and analyze the variation of ion flux distribution within the channel with respect to the angle of incidence. It is observed that at the angle of incidence corresponding to the channeling shoulder, the primary channeling focus overlaps with lattice atoms and dramatically enhances the ion flux density at atomic sites, increasing the ion–atom close encounter probability. We show that the so increased close encounter probability originates high near-surface shoulders in channeling.

► We study the effect of ion flux-focusing on origin of channeling shoulders.
► We simulate variation of ion channeling flux focus with incidence angle.
► Near channeling critical angle, flux focus superimposes on atomic sites.
► Ion flux focus superposition with atomic sites originates shoulders.