Variations in the Raman Spectrum as a Function of the Number of Graphene Layers

We studied variations in the Raman spectrum as a function of the number of graphene layers by using micro-Raman spectroscopy and atomic force microscopy (AFM). The sample preparation was done by micromechanical cleaving of natural graphite on an ∼300 nm SiO2 layer. The Raman G band (∼1580 cm−1), G ∗ band (∼2450 cm−1) and 2D band (∼2700 cm−1) varied as functions of the number of graphene layers. The Raman 2D band was especially sensitive to the number of graphene layers. These features are related to the electronic band structure of graphene. Moreover, areas of different numbers of graphene layers were clearly identified using spatially-resolved micro-Raman imaging spectroscopy. PACS numbers: 73.22.-f, 78.30.-j, 78.66.-