Secondary-Ion Emission in Grazing Collisions between Highly Charged Ions and Surfaces

In order to study the potential sputtering processes in collisions between highly charged ions and surfaces, we conducted secondary-ion mass spectroscopy, measured simultaneously with the scattered atoms at grazing incidence angles. Efficient proton emission was observed in both metal (A1) and wide-gap semiconductor (GaN) surfaces. We conclude that the electron capture by highly charged ions above the surface caused the efficient proton emission. The three-dimensional momentum of protons emitted from the surface was successfully visualized, and the anisotropic angular distribution of the momentum was observed. Contrary to the adsorbed atoms or molecules, no efficient emission of the substrate atoms was observed in the metal (A1) surface.