Surface Structure on Ar + -Ion Irradiated Graphite by Scanning Probe Microscopy

The surface structure of a highly oriented pyrolytic graphite (HOPG), irradiated by Ar + ions with an ion energy of 0.5–1.0 keV at doses below 5×10 11 ions/cm 2 during annealing, was characterized by scanning probe microscopy. The ion-induced hillocks were observed by both scanning tunneling microscopy (STM) and atomic force microscopy (AFM) after the ion irradiation, the heights of which, measured by STM, were larger than that measured by AFM in the tapping mode. The hillocks were recovered distinguishably by annealing above 470 K. Almost 85% of the hillocks disappeared after annealing at 1270 K and they disappeared completely after annealing above 1770 K. The behavior of defects produced by ion-irradiation in HOPG during annealing is discussed.