Nanoscale mapping of noise-source-controlled hopping and tunneling conduction in domains of reduced graphene oxide

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We report a nanoscale mapping of noise-source-controlled transport characteristics in the domains of reduced graphene oxide by utilizing noise-source imaging strategies. In this method, current and noise images were measured simultaneously using a scanning noise microscopy and analyzed to map sheet−resistances (R□) and noise−source densities (neff). The maps showed the formation of conducting and insulating domains, where the insulating domains exhibited up to three-four orders of higher R□ and neff than those of conducting domains. Interestingly, the sheet−conductance (Σ□) and neff followed rather opposite power−law behaviors like Σ □∝ neff−0.5 and Σ□ ∝ neff0.5 in conducting and insulating domains, respectively, which could be attributed to the difference in mesoscopic charge transport mechanisms controlled by neff in domains. Notably, high biases resulted in the increased conductance (ΔΣ□) and decreased noise−source density (Δneff) following a relationship like ΔΣ□ ∝−Δneff0.5 for both conducting and insulting domains, which could be explained by the passivation of noise−sources at high biases. Furthermore, ΔΣ□versus Δneff plot on the annealing also followed a power−law dependence (ΔΣ□ ∝−Δneff0.5) in conducting domains, which could be attributed to carrier generation on the annealing. Our results about mesoscopic charge transports could be significant advancements in fundamental researches and applications.