Ultrapure multilayer graphene in bromine-intercalated graphite

We investigate the optical properties of bromine-intercalated highly orientated pyrolytic graphite (Br-HOPG) and provide an interpretation of the data. We observe absorption features below 620 meV which are absent in the absorption spectrum of graphite. Comparing our results with those of theoretical studies on graphite, single- and bilayer graphene, as well as recent optical studies of multilayer graphene, we conclude that Br-HOPG contains the signatures of ultrapure bilayer graphene, ultrapure single-layer graphene, and graphite. The observed supermetallic conductivity of Br-HOPG is identified with the presence of very high mobility (121000 cm2V^-1s^-1 at room temperature and at very high carrier density), multilayer graphene components in our sample. This could provide an avenue for single- and multilayer graphene research.