Physical and chemical mechanisms affecting electrical conductivity in reduced graphene oxide films

• Electrical conductivity (σ) of graphene oxide (GO) & reduced graphene oxide (rGO)
• “σ” of GO and rGO varies with film thickness.
• “σ” of GO and rGO varies with the degree of film roughness.
• “σ” of GO and rGO varies with film percentage of functionalities.
• Micro-mechanical exfoliation influences the crystallinity of the films.

This article focuses on the influence of surface topography (roughness), surface chemistry (carbon and oxygen functional groups) and physical (film thickness) parameters on the electrical conductivity of graphene oxide (GO) and reduced graphene oxide (rGO) films. This study was carried out to understand how changes in chemistry, roughness and film thickness, arising from the reduction process, alter the electrical properties of the films. Improved understanding is needed to control and optimise these parameters in graphene/rGO films for future applications where targeted property performance is needed. Films with smooth surfaces, measured using confocal imaging, and lower thicknesses have been shown to possess higher electrical conductivity. X-ray diffraction patterns shows minor changes in d-spacing, though improvements in crystal perfection, orientation and crystallinity could be concluded. X-ray photoelectron spectroscopy shows a significant decrease in the oxygen present at the surface as the films are exfoliated to reduce their thickness. Conductivity improves as the materials become increasingly defect-free, achieved by careful control of reduction and post-processing techniques. Ideal practical conductivity is achieved for films of 4 μm thickness: beyond this point, no practical gains are made (about 25 exfoliation trials from the bulk cast film).