C. Y. Cheah, C. Gómez-Navarro, L. C. Jaurigue, A. B. Kaiser
We report and analyze low-temperature measurements of the conductance of partially disordered reduced graphene oxide, finding that the data follow a simple crossover scenario. At room temperature, 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(-E_0/E)^(1/3) field-driven (Shklovskii) 2D VRH conductance behaviour when the electric field E exceeds a specific crossover value E_C (T)_2D = (E_a E_0^(1/3) /3)^(3/4) determined by the scale factors E_0 and E_a 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.
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http://arxiv.org/abs/1305.0315
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