STM studies of HCl-induced surface damage on highly oriented pyrolytic graphite

Scanning tunneling microscopy (STM) with atomic scale resolution has been a pplied to study surface defects in highly oriented pyrolytic graphite (HOPG ) which have been produced by impact of 150 eV singly and multiply charged Ar ions (charge state up to 9+). The most prominent surface defects axe pro trusions. Their area density is in good agreement with the applied ion dose , implying that about every single ion impact causes one protrusion. A (roo t3 x root3) R 30 degrees surface reconstruction, as characteristic for inte rstitial defects in HOPG, is observed in the vicinity of most defects. As t he most remarkable result we find that the measured size of the hillocks (m ean diameter and height) increases with projectile charge state.