Investigating the nano-tribological properties of chemical vapor deposition-grown single layer graphene on SiO2 substrates annealed in ambient air

Abstract

Nano-tribological properties of graphene have attracted a lot of research interest in the last few years. In this work, X-ray photoelectron spectroscopy was used to study the distribution of chemical groups in chemical vapor deposition (CVD) of single layer graphene transferred onto a 90 nm SiO₂/Si substrate. It was demonstrated that the graphene was oxidized after thermal treatment at 520 °C in ambient air, as indicated by the formation of CO and C–OH bonds. Significantly enhanced D-band and decreased 2D-band were found in the Raman spectrum. Blue shift occurred for the G-band and 2D-band after thermal oxidation. The nano-tribological properties of graphene before and after thermal oxidation were studied with atomic force microscopy. A remarkable increase of friction was found on the surface of graphene after thermal oxidation. This was contributed to by the increased adhesion and decreased Young's modulus of the functionalized graphene, inducing the increase of contact stiffness. In addition, the adhesion force between the tip and the samples was discussed as an important factor affecting tribological properties on the nano-scale.