OBSERVATION OF THREEFOLD SYMMETRY IMAGES DUE TO A POINT-DEFECT ON A GRAPHITE SURFACE USING SCANNING TUNNELING MICROSCOPE (STM)

This paper reports an observation of a point defect on a graphic surface with a threefold-symmetric electronic perturbation, which is a required characteristic of a point defect predicted by a simulation. A scanning tunneling microscope (STM) was used. Due to the covalent system of graphite, the propagation length of the electronic perturbation is only one tenth of that in the free electron system and its symmetry reflects the crystallographic symmetry. By considering the effects of the electronic enhanced dimers, this electronic perturbation can be interpreted as an initial formation stage of a (root 3 x root 3)R30 degrees superlattice which is often observed in the neighborhood of larger defects.