Theory of the evolution of 2<i>D</i> band in the Raman spectra of monolayer and bilayer graphene with laser excitation energy

Abstract

Abstract A double‐resonance process gives rise to the 2 D band in the Raman spectra of monolayer and bilayer graphene. Based on the electronic and vibrational dispersion energies of graphene, the wavenumbers of the 2 D band were calculated under different laser excitation energies (from 1.0 to 4.4 eV). Calculated results are in good agreement with experimental data and reproduce the experimental dispersion slope of the 2 D band very well. The calculated wavenumbers of the 2 D band do not show a linear dependence on the laser excitation energies. Moreover, it is explained that the lowest wavenumber peak of the 2 D band of the bilayer graphene, which is composed of four components, has the largest slope with laser excitation energy. Copyright © 2009 John Wiley &amp; Sons, Ltd.