Lateral force microscopy study of a mixed-layer graphene structure

Using a commercial (Park Systems, NX-10) atomic force microscope (AFM), we produced a mixed-layer graphene structure composed of one- to four-layer domains by folding a monolayer graphene. After, we obtained several lateral force microscopy (LFM) friction images of the fabricated structure in order to verify its atomic configurations under ambient conditions. LFM friction images show that the topmost layers of the respective domains have different in-plane crystallographic orientations. Based on a statistical analysis, we will show that the cut edges of the mixed-layer graphene tend to have zigzag or armchair directions while the folded lines do not reveal the tendency. In addition, certain strips have also been observed concurrently in the LFM images of graphene; it can result in the serious misinterpretation of the LFM images of atomic scale friction. We will discuss about the cause of the phenomenon and suggest a simple method to avoid it.