Aspects of Intercalation of Fluorine and Metal Fluorides into Graphite

The peculiar reactivity of fluorine with graphite can be related to some characteristic parameters of this element. The competition between strong C-F bonds in covalent graphite fluorides and weak semi-ionic bonds in graphite intercalation compounds is pointed out. The different experimental routes for the intercalation of fluorine and metal fluorides into graphite are reviewed. The oxidation state, the environment of the metal and the nature of the bonding between the intercalated species and carbon can be approached by various techniques, including XANES, EXAFS, and XPS spectroscopies. The structural relationships between the graphene sublattice and the intercalate sublattice can be pointed out on the basis of single crystal data. Concerning the transport properties, acceptor-GICs have proved to be very appropriate to investigate the effects of disorder and reduced dimensionality. The charge transfer which accompanies the insertion of fluorinated species between the graphene layers can be evaluated from optical reflectivity and the subsequently calculated conductivity is compared with direct electrical data. In fibrous samples, disorder-induced phenomena are evidenced in both electrical and thermal transport properties. The electrical resistivity results can be analyzed in the framework of weak localization and carrier-carrier interaction models for 2D disordered electron systems.