Scanning tunnelling microscopy with atomic scale resolution was applied to study surface defects in highly oriented pyrolytic graphite which were produced by impact of 150eV singly and multiply charged Ar ions (charge state up to 9+). The most prominent surface defects were protrusions. Their area density was in good agreement with the applied ion dose, implying that about every single ion impact causes one protrusion. A (√3 x √3)R30° surface reconstruction, as characteristic for interstitial defects in highly oriented pyrolytic graphite, was observed in the vicinity of most defects. As the most remarkable result It was found that the measured size of the hillocks (mean diameter and height) increases with projectile charge state.

STM Studies of HCl-Induced Surface Damage on Highly Oriented Pyrolytic Graphite. G.Hayderer, S.Cernusca, M.Schmid, P.Varga, H.P.Winter, F.Aumayr: Physica Scripta, 2001, T92, 156-7