Electronic Raman scattering in graphite and single-layer and few-layer graphene

Abstract

We investigated polarization-resolved electronic Raman scattering in different graphitic structures, including bulk graphite and single-layer and few-layer graphene. For all investigated samples, the broad continua of interband electronic transitions were detected at an energy $\ensuremath{\sim}0.35$ eV, while they were expected to be at $\ensuremath{\sim}6$ eV [Phys. Rev. B 88, 085416 (2013)]. The symmetry of the observed excitations corresponds to the ${A}_{2g}$ irreducible representation. A quasilinear behavior of the Raman response is observed at low energies in all cases at room temperature, in agreement with performed tight-binding calculations. High-energy features at $\ensuremath{\sim}0.8$ eV are detected in the spectra of graphite and few-layer graphene. They are attributed to interband transitions in the vicinity of the $K$ point, which involve electronic bands split by interlayer interaction. The effects of the substrate type, defect amount, and doping on the continuum line shape and symmetry are discovered. The silent layer-breathing mode is observed in a single-layer graphene. The results evidence that the electronic light scattering in graphitic structures without an external magnetic field is a powerful tool, which provides a variety of data on the structure and symmetry of low-energy electronic excitations.