STM OF CRCL3-GRAPHITE INTERCALATION COMPOUNDS - ISLANDS, GRAPHITE INPLANE DEFECTS

Samples of stage-2 chromium chloride graphite intercalation compounds have been studied by Scanning Tunneling Microscopy (STM) with atomic resolution. Due to the existence of Daumas-Herold domains with one and two graphite layers on the guest layer closest to the surface, which exhibit different STM images, the first direct evidence is given for the existence of small intercalated islands. The island shape is shown to be very complicated. In addition, a new kind of defects has been observed in some images, where extra carbon atoms give rise to the presence of heptagons and triangles inside the hexagonal lattice of the carbon layers. These defects could be responsible for the well known particular chemical properties of Kish graphite and for the shift of its Fermi level relative to pristine graphite, as deduced from magnetic susceptibility experiments.