Study of nano-scale surface modification processes induced by slow highly charged ion collisions

We have studied about nano-scale surface modification processes induced by slow highly charged ion collisions on highly oriented pyrolytic graphite (HOPG). The diameter of hillock induced by an ion increases with increasing potential energy of incident ions. The shape of induced modifications has changed from a hillock-like to a caldera-like between Bi70+ and Bi75+. In gradient incidence experiments, we observed interesting surface modifications that are asymmetric hillocks and several hillocks induced by an incident ion.