Quantum-dot-like electrical transport of free-standing reduced graphene oxide paper at liquid helium temperatures

We present the results of a study of the electrical properties of macroscopic free-standing reduced graphene oxide paper (RGOP) with a 60 % fraction of sp2-carbons at liquid helium temperatures. Graphene domains form an array of quantum dots that determine material properties. At low temperatures, the electrical conductivity of the RGOP can be described by the model of tunneling of charge carriers through a disordered quasi-2D quantum dot array. In the free-standing RGOP at the temperature of 4.2 K, the charge carriers are localized in the quantum dots due to the Coulomb blockade. The effective localization length (-5-8 nm) of charge carriers coincides with the average size of the sp2-carbon regions (-6-8 nm). The transfer of charge carriers in the RGOP at liquid helium temperatures occurs due to tunneling between energetically close graphene domains, which are not nearest neighbors in space and are rather far from each other (up to-100 nm).