SCANNING TUNNELING MICROSCOPY OBSERVATION OF LOCAL DAMAGES INDUCED ON GRAPHITE SURFACE BY ION-IMPLANTATION

Highly oriented pyrolitic graphite was implanted with 50 keV argon ions. Low ion doses were deposited in order to observe, with the scanning tunneling microscope, surface damages due to single-ion impacts. Ion impacts were revealed by the formation of hillocks on the graphite surface. The raising of the surface is attributed to internal stresses which develop in the volume surrounding the ion track as damages and lattice defects are created by the collision cascade process. Structural transformations are induced by ion implantation: On the hillock the graphite structure was lost and no atomic organization of the surface was evidenced. Surface reconstructions and superstructures were also imaged next to some hillocks.