Enhancing the electrical conductivity of vacuum-ultraviolet-reduced graphene oxide by multilayered stacking

Vacuum-ultraviolet light irradiation under a high vacuum is a facile method to reduce graphene oxide (GO) sheets and therefore to enhance their electrical conductivity. The aim of this study was to investigate the local electrical properties of a reduced graphene oxide (rGO) monolayer and bilayer by using conductive atomic force microscopy (CAFM). Both the lateral and vertical CAFM measurements showed a higher current signal on the rGO bilayer than on the rGO monolayer. The enlargement of the tip contact area significantly affected the vertical CAFM measurements and enhanced the current signal in the bilayer regions. However, when performing the lateral CAFM measurements, the enlarged tip contact area had no obvious influence on the current signal. The increase in the current signal can be ascribed to the intrinsic enhancement of the electrical conductivity on the rGO bilayer. These results suggested that the stacked rGO sheets formed the new conductive paths for the carrier transportation in the lateral direction. This process can be further applied in producing microconductive patterns in multilayered GO.