title: Unusual infrared-absorption mechanism in thermally reduced graphene oxide.
abstract: Infrared absorption of atomic and molecular vibrations in solids can be affected by electronic contributions through non-adiabatic interactions, such as the Fano effect. Typically, the infrared-absorption lineshapes are modified, or infrared-forbidden modes are detectable as a modulation of the electronic absorption. In contrast to such known phenomena, we report here the observation of a giant-infrared-absorption band in reduced graphene oxide, arising from the coupling of electronic states to the asymmetric stretch mode of a yet-unreported structure, consisting of oxygen atoms aggregated at the edges of defects. Free electrons are induced by the displacement of the oxygen atoms, leading to a strong infrared absorption that is in phase with the phonon mode. This new phenomenon is only possible when all other oxygen-containing chemical species, including hydroxyl, carboxyl, epoxide and ketonic functional groups, are removed from the region adjacent to the edges, that is, clean graphene patches are present.
authors.affiliation: Department of Materials Science and Engineering, University of Texas at Dallas, Richardson, Texas 75080, USA.
authors.forename: M
authors.initials: M
authors.lastname: Acik
authors.forename: G
authors.initials: G
authors.lastname: Lee
authors.forename: C
authors.initials: C
authors.lastname: Mattevi
authors.forename: M
authors.initials: M
authors.lastname: Chhowalla
authors.forename: K
authors.initials: K
authors.lastname: Cho
authors.forename: Y J
authors.initials: YJ
authors.lastname: Chabal