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

Abstract 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 ( n eff ). The maps showed the formation of conducting and insulating domains, where the insulating domains exhibited up to three-four orders of higher R □ and n eff than those of conducting domains. Interestingly, the sheet−conductance ( Σ □ ) and n eff followed rather opposite power−law behaviors like Σ □ ∝  n eff −0.5 and Σ □ ∝  n eff 0.5 in conducting and insulating domains, respectively, which could be attributed to the difference in mesoscopic charge transport mechanisms controlled by n eff in domains. Notably, high biases resulted in the increased conductance (Δ Σ □ ) and decreased noise−source density (Δ n eff ) following a relationship like Δ Σ □ ∝−Δ n eff 0.5 for both conducting and insulting domains, which could be explained by the passivation of noise−sources at high biases. Furthermore, Δ Σ □ versus Δ n eff plot on the annealing also followed a power−law dependence (Δ Σ □ ∝−Δ n eff 0.5 ) 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.