Preparation and characterization of graphene and few-layer graphene

Few-layer graphene was prepared from highly oriented pyrolytic graphite by micromechanical cleavage and transferred to the silicaon coated with silicon dioxide (SiO2/Si). The thickness of graphene on the SiO2/Si support was investigated by color and contrast variations under an optical microscope. Atomic force microscopy and Raman spectroscopy were used to determine the number of layers. Results show that a monolayer, double layers and multiple layers of graphene were prepared. The optical microscope images can give a satisfactory identification of the graphene thickness on SiO2/Si. In the Raman spectrum the 2D band is narrower and G band is weaker for double layers than that for multiple layers. Chemical vapor deposition was also used to grow large area (~cm2) graphene. However, micromechanical cleavage is a more simple method to prepare graphene.