Raman spectroscopy of graphene and graphite: Disorder, electron–phonon coupling, doping and nonadiabatic effects

We review recent work on Raman spectroscopy of graphite and graphene. We focus on the origin of the DD and GG peaks and the second order of the DD peak. The GG and 2D2D Raman peaks change in shape, position and relative intensity with number of graphene layers. This reflects the evolution of the electronic structure and electron–phonon interactions. We then consider the effects of doping on the Raman spectra of graphene. The Fermi energy is tuned by applying a gate-voltage. We show that this induces a stiffening of the Raman GG peak for both holes and electrons doping. Thus Raman spectroscopy can be efficiently used to monitor number of layers, quality of layers, doping level and confinement.