Cutting of Oxidized Graphene into Nanosized Pieces

We report a simple approach to producing nanosized graphene on the basis of chemical oxidation of a graphene sheet followed by cutting of the sheet using a scanning probe microscopic (SPM) manipulation technique. The structural and electronic properties of the oxidized sheet are characterized by noncontact atomic force microscopic (NC-AFM) imaging and SPM spectroscopy under ultrahigh vacuum conditions. Regularly spaced linear defects with a spacing of 5-10 nm and a length of >100 nm were found on the sheet, which can be attributed to the result of linear arrangement of epoxide functional groups. The cutting experiments are performed on sheets in which the linear defects were observed in advance. Cutting is initiated by a point contact between the preoxidized sheet and the AFM probe. The local mechanical stress caused by the point contact leads to rupture of the sheet, which proceeds linearly along the linear defect of the epoxide groups. We propose that the linear defect structures can be used as a template to determine the cutting direction of the sheet. According to recently proposed theoretical predictions, the linear epoxide groups have preferential alignment along a zigzag direction in the graphene lattice, and therefore, the cut edge shape could have well-defined alignment along the zigzag direction. This cutting procedure of the graphene sheet could be a useful method for the production of nanosized graphene with well-defined edges.