Frictional and electrical characterization of nanostructures induced by slow highly charged ion bombardment of HOPG surfaces

Bombardment of a highly ordered pyrolitic graphite (HOPG) surface with slow, highly charged ions (Arq+ and Xeq+) can be considered as a model system for surface layer modification. The topographic identification of the induced surface by atomic force microscopy (AFM) measurement in conventional tapping mode is difficult. However, using Friction Force Microscopy, where the cantilever is scanned perpendicular to its long axis in contact mode, the ion impact locations (dots) can be revealed as zones of enhanced friction in both, topographic and friction images. For quantitative lateral force measurements, an improved wedge calibration method is employed. The microscopic friction force coefficient of the ion impact locations on the surface has been determined as a function of ion charge state. The impact dot size detected by friction images clearly depend on the ion charge state. For electrical characterization of the ion bombarded surface, we employed conductive AFM, which clearly showed an increased conductivity at ion impact locations.