Behaviour of charge carriers in thermally reduced graphene oxide: Magnetism and ambipolar transport

We report a research study on reduced graphene oxide conducted with electron paramagnetic resonance and impedance spectroscopy techniques. Coupling of the two experimental methods allowed us to obtain detailed information on the charge carrier transport in the graphene material and make an attempt at explaining the peculiar behaviour of para- and ferromagnetic properties of the studied system. Two scattering processes characterized by different dynamics were found. An ambipolar-like character of the charge transport was observed with transition between holes and electrons driven by the bias voltage, temperature, and adsorption. Electron paramagnetic resonance spectra showed a typical signal from localized centers as well as weak ferromagnetism. The latter correlates with the change of carriers' polarity. This indicates that ferromagnetic coupling between the localized states in graphene is related to the type of charge carriers. Such behavior points to the similarity of reduced graphene oxide to the dilut...