Nano-manipulation On Individual Graphene Oxide Sheets With A Heated AFM Tip

Graphene, a2D sheet of sp2-hybridized carbon, has been interested by manyresearchers from different fields. Great efforts have been made in studying its distinctiveelectronic, optical, magnetic, thermal, and mechanical properties, aimed at potentialapplications of graphene in various kinds of devices. Graphene oxide (GO) as an importantprecursor for large-scale synthesis of free-standing graphene sheets is electricallyinsulating. To make it electrically active, the GO is conducted mostly by using chemicalreduction or thermal treatment.To exploit the broad application of graphene, a key issue is to pattern the graphene-related materials in nanometer scale. Many methods, including scanning-probe-basednanolithography techniques, have been used. Recently, Wei et al. reported that a heated tipof atomic force microscope (AFM) can locally reduce the GO, and pattern nanoscale areasof the reduced GO sheet at high speed. The technique, which was well related to thermalnanolithography with heated AFM tips, can locally induce chemical reactions, depositmaterial on a surface, and modify a polymer film. However, the factors influencing thelocal thermal reduction of GO sheets have not been fully explored.In this paper, the factors that influence the local thermal reduction of GO sheets wereinvestigated. Heated AFM tips were employed to thermally reduce GO into electricalconductive nanostructures, which were verified by lateral force microscopy and scanningpolarization force microscopy. The tip temperature, heating time, and loading forceapplied by the AFM tip were found to play important roles on the thermal reduction of GO,while the effect of environmental humidity is neglectable. The presence of grapheneripping was observed and recorded，and the thermal conductivity through the monatomicgraphene layer was explored.