Diffusion and intercalation of fluorine into highly oriented pyrolytic graphite: An in situ ESR study

An in situ ESR study of specially cut highly oriented pyrolytic graphite (HOPG) indicates dramatic changes in the ESR line shape (A/B ratio) and intensity upon exposure to a fluorine atmosphere. The results can be interpreted by the formation of a macroscopic intercalation layer and the advance of a boundary separating the intercalated and nonintercalated HOPG. Using a theoretical model previously developed for the ESR of layer-substrate systems, we extract the thickness of the intercalated layer as a function of the exposure time and the diffusion coefficient of fluorine into the HOPG.