Comparison of temperature dependences of electrical conductivity of composite rGO-SWNT film with rGO and SWNT films

Temperature dependences of electrical conductivity of reduced graphene oxide composite with single-walled nanotubes (rGO-SWNTs) and rGO films has been studied in the temperature range of 25-290 K. Both films were obtained by vacuum filtration of aqueous suspensions. Temperature dependences of conductivity of films were found similar to the conductivity observed in disordered semiconducting systems. It was demonstrated that the behavior of the conductivity temperature dependence of pure rGO, SWNTs and composite film is different. The temperature dependences of the resistance R(T) of the films were analyzed within the framework of the variable range hopping (VRH) transport in which electron motion is due to the thermo-activated quantum tunneling between localized states. Two-dimensional Mott VRH (Mott 2D VRH) and Efros-Shklovskii VRH (ES VRH) models were applied for analysis. Mott 2D VRH was observed for rGO-SWNT film in the interval of 25-200 K. At higher temperatures R(T) of rGO-SWNT was fitted with Arrhenius-like equation describing electron activation from localized states to delocalized ones. R(T) of the rGO film followed the Mott 2D VRH model from 165 to 290 K, however, at lower temperatures ES VRH model was exploited. From approximation of R(T) by these models the parameters of the electron transport in rGO-SWNT and rGO films were estimated. It was suggested that nanotubes in rGO-SWNT composite serve as conductive bridges among rGO sheets enhancing the conductivity as compared to rGO. The conductivity of rGO also influences on the composite properties because 2D character of electron motion is kept in sharp contrast to SWNT film which demonstrated three-dimensional Mott VRH electron transport in the same temperature range.