MeV-ion axial surface-channeling from an electron irradiated KCl(0Â 0Â 1) surface

Surface-channeling of protons incident with 5 mrad on an electron-irradiated surface is investigated using a 0.55 MeV beam of protons. The target surface is KCl(0 0 1), which is damaged by electron-stimulated desorption with 5 keV electron irradiation. The direction of the incident beam is adjusted along the 〈1 0 0〉 and 〈1 1 0〉 channeling conditions and the channeling-dips of the scattering yields are observed. The irradiation dose-dependence of the minimum yields and widths of the dips is measured. Two dips are compared, i.e., for the 〈1 0 0〉 and 〈1 1 0〉 channelings. By increasing the irradiation dose up to 2 × 1016 cm−2, the dip around the 〈1 0 0〉 axis becomes opened, but that of the 〈1 1 0〉 axis becomes shallow. The irradiated surfaces are observed to have many overlapped terraces of sub-micron with monolayer steps. The surface morphology deformed by the irradiation effects to truncate trajectories of the 〈1 0 0〉 channeling protons. This roughness of the surface is more effective for the trajectories of the 〈1 1 0〉 channeling protons. The protons incident on the rough surface along the 〈1 1 0〉 axis are not reflected from the atomic row but reflected by a potential of the surface with steps. Results by a simple computer simulation of the trajectories of protons at stepped surfaces also indicate the scattering processes.