Chemical synthesis by ion implantation: Fluorine intercalated graphite

Abstract

The c -face of highly oriented pyrolytic graphite (HOPG) has been implanted with a high energy beam (25 keV) of F + ions at a fluence of 3×10 17 ions/cm 2. The implanted face turns blue and exhibits modified optical properties (sharp Drudè edge, high reflectivity below the edge) associated with metallic behavior. The optical properties are roughly the same as those engendered in third stage intercalation compounds of graphite with electron acceptors and by analogy with these compounds the fluorine is thought to be present largely as F − ions. X-ray photoelectron spectra of the implanted host have also been obtained. Relative signal intensities of the F 1s and F 2s levels reflect the strong F depth concentration gradient in the samples. The large C 1s:F 1s intensity ratio implies that only very modest etching of the sample surface has taken place during implantation. The sputtering coefficient of graphite is estimated from XPS data to be no greater than 0.3 for these implantation conditions.