Atomically Resolved Imaging of the Defect Structure on Graphite After Oblique Single-Ion Impact

Using scanning tunnelling microscopy (STM), defect structures on (0001) graphite surfaces after irradiation with 132 Xe ions are studied. Ion fluences of typically 10 11 ions/cm 2 with energies ranging from 50 keV to 90 keV were implanted. The angle of incidence (relative to the surface normal) was varied between 0° and 75°. Two types of isolated, hillock-shaped defects were observed, the arrangement and number of which are compared with computer-simulated linear-collision cascades. The hillock shape of the defects is explained by the formation of interstitial clusters between the carbon layers. The measured hillock volumes are attributed to the expansion volumes of single interstitials near the surface.