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

摘要

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-square) 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-square and n(eff) than those of conducting domains. Interestingly, the sheet-conductance (Sigma(square)) and n(eff) followed rather opposite power-law behaviors like Sigma(square) proportional to n(eff)(-0.5) and Sigma(square) proportional to 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 (Delta Sigma(square)) and decreased noise-source density (Delta n(e)(ff)) following a relationship like Delta Sigma(square)proportional to -Delta n(eff)(0.5) for both conducting and insulting domains, which could be explained by the passivation of noise-sources at high biases. Furthermore, Delta Sigma(square) versus Delta n(eff) plot on the annealing also followed a power-law dependence (Delta Sigma(square) proportional to -Delta 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. (C) 2019 Elsevier Ltd. All rights reserved.