Temperature dependence conductivity of r-GO in the presence of UV irradiation

Graphene oxide (GO) was synthesized by the thermal decomposition of sucrose and was reduced by thermal annealing under a nitrogen atmosphere. We report on the conductivity of reduced graphene oxide (r-GO) thin films in the temperature range 20K < T < 300K. The conductivity measurements were performed in vacuum under dark conditions and in the presence of UV irradiation of two different wavelengths (365nm and 254nm). Our results confirm that UV irradiation increases the conductivity, with the short wavelength radiation showing a larger conductivity increase. During the cooling run, the conductivity showed a metallic response at high temperatures, while at low temperatures there was a switch to semiconducting behavior. Short wavelength UV irradiation extended this metallic behavior to lower temperatures compared to that measured under dark conditions. During the heating run however, the conductivity response was semiconducting indicating that the metallic response could have shifted to higher temperatures beyond 300K. Preliminary results indicate that the response to UV irradiation is slow, taking several minutes or even hours to reach saturation. We shall present our analysis on possible conduction mechanisms in r-GO and the response/recovery times to UV irradiation.