Charge Transport in Thick Reduced Graphene Oxide Film

We have investigated temperature-dependent charge transport behavior in thick reduced graphene oxide (RGO) film. Our results show that charges transport through two parallel percolating conducting pathways. One contains large disordered regions as one of its constituents, so its conductance is determined dominantly by variable range hopping (VRH). The other is composed of small and medium disordered regions and crystalline sp(2) domains, so its conductance is determined by a serial connection of quantum tunneling and thermal activation. The more oxygen functional groups are removed from GO film upon progressive reduction, the lower the potential barriers between the crystalline sp(2) domains and disordered regions become. The contribution of thermal activation to total conductance does not appear evidently for highly reduced GO film having low potential barriers, but thermal activation causes the conductance of moderately reduced film to change continuously, even at low temperatures where the VRH is almost frozen out.