title: Conductance of partially disordered graphene: crossover from temperature-dependent to field-dependent variable-range hopping.
abstract: We report an analysis of low-temperature measurements of the conductance of partially disordered reduced graphene oxide, finding that the data follow a simple crossover scenario. At room temperature, the conductance is dominated by two-dimensional (2D) electric field-assisted, thermally driven (Pollak-Riess) variable-range hopping (VRH) through highly disordered regions. However, at lower temperatures T, we find a smooth crossover to follow the exp(-E0/E)(1/3) field-driven (Shklovskii) 2D VRH conductance behaviour when the electric field E exceeds a specific crossover value EC(T)(2D) = (EaE(1/3)0 /3)(3/4) determined by the scale factors E0 and Ea for the high-field and intermediate-field regimes respectively. Our crossover scenario also accounts well for experimental data reported by other authors for three-dimensional disordered carbon networks, suggesting wide applicability.
authors.affiliation: MacDiarmid Institute for Advanced Materials and Nanotechnology, School of Chemical and Physical Sciences, Victoria University of Wellington, PO Box 600, Wellington 6140, New Zealand.
authors.forename: C Y
authors.initials: CY
authors.lastname: Cheah
authors.forename: C
authors.initials: C
authors.lastname: Gómez-Navarro
authors.forename: L C
authors.initials: LC
authors.lastname: Jaurigue
authors.forename: A B
authors.initials: AB
authors.lastname: Kaiser