A scanning tunnelling microscopic investigation was made of surfaces which had been bombarded with Ar+ ions that had energies which were near to the threshold of 40 to 100eV. In order to understand the effect of Ar atoms, trapped between the graphite basal planes, upon the scanning tunnelling microscopic images, the trapped atoms were evaporated by heating the surface to 600C after 50eV Ar+ impacts. It was found that such ion impacts created hillocks of various sizes in the scanning tunnelling microscopic images. The latter arose from an enhanced charge density at vacancy and interstitial defect sites.

J.R.Hahn, H.Kang: Surface Science, 1996, 357-358, 165-9