Nano-structure formation due to impact of highly charged ions on HOPG

Highly ordered pyrolitic graphite (HOPG) was irradiated with slow highly charged Arq+ and Xeq+ ions in a kinetic energy range of 150–360 keV and has been observed by scanning probe microscopy. Nano-sized hillock-like structures are found for all charge states and kinetic energies with both the scanning tunneling microscope and the atomic force microscope. However in the latter case, the dependence of the detected structures on scan conditions points towards a surface modification which manifests itself only in frictional forces and therefore in height measurement artifacts. Furthermore the generated defects are not stable but can be erased by continuous scanning in contact mode.