Observation of an HCI-induced nano-dot on an HOPG surface with STM and AFM

We have observed highly oriented pyrolytic graphite (HOPG) irradiated with highly charged ions (HCIs) with a scanning probe microscope. The same impact site was observed with both the scanning tunnelling microscope (STM) and atomic force microscope (AFM) modes. In the non-contact mode AFM image, protrusion-like dots have been observed as well as in the STM observations. The dot size (diameter) and height observed with the AFM mode were nearly equal to that with the STM mode. The present observation clearly indicates that an HCI impact induces topographic modification on an HOPG surface.