Electric field and oxygen concentration-dependent transport properties of nano-graphene oxide

Electrical transport properties of the nano-graphene oxide were investigated by measuring current-voltage characteristics in the wide temperature range of 15 K∼450 K. The n-GO is composed of nanometer-sized intact graphene-like sp2 domains embedded in the sp3 matrix which acts as a charge transport barrier between the highly conductive sp2 domains. The oxygen in the n-GO has the concentration of 4.43 at% in the form of oxygen functional groups. Below the conduction band, four discontinuous localized states with the activation energies of 1.92 meV, 3.27 meV, 5.54 meV, and 6.58 meV were observed. These activation energies decrease with decreasing oxygen concentration and increasing external electric field in the n-GO material. Moreover, we found that the direct tunneling of charge carrier through the sp3 barrier was a dominant transport mechanism for the n-GO material. Also, unlike the activation energy of charge carrier, the transport barrier was independent of both the concentration of the oxygen functional groups and external electric field. The transport barrier was mainly determined by insulation property of the sp3 structure.