Evolution of Raman G and G′ (2D) modes in folded graphene layers
Date of Issue2014
School of Physical and Mathematical Sciences
Bernal- and non-Bernal-stacked graphene layers have been systematically studied by Raman imaging and spectroscopy. Two dominant Raman modes, G and G ′ (or 2D ), of folded graphene layers exhibit three types of spectral features when interlayer lattice mismatches, defined by a rotational angle varies. Among these folded graphene layers, the most interesting one is the folded graphene layers that present an extremely strong G mode enhanced by a twist-induced Van Hove singularity. The evolution of Raman G and G ′ modes of such folded graphene layers are probed by changing the excitation photon energies. In this paper, doublet splitting of the G ′ mode in a folded double-layer (1 + 1) and of the G mode in a folded tetralayer (2 + 2) graphene are observed and discussed. The G ′ mode splitting in folded double-layer graphene is attributed to the coexistence of inner and outer scattering processes and the trigonal warping effect as well as further downward bending of the inner dispersion branch at a visible excitation energy. The two peaks of the G mode in folded tetralayer graphene are assigned to Raman-active mode (E 2g ) and lattice mismatch activated infrared-active mode (E 1u ), which is further verified by the temperature-dependent Raman measurements. Our study provides a summary and discussion of Raman spectra of Bernal- and non-Bernal-stacked graphene layers and further demonstrates the versatility of Raman spectroscopy for exploiting electronic band structures of graphene layers.
Physical review B
© 2014 American Physical Society. This paper was published in Physical Review B and is made available as an electronic reprint (preprint) with permission of American Physical Society. The paper can be found at the following official DOI: http://dx.doi.org/10.1103/PhysRevB.89.235430. One print or electronic copy may be made for personal use only. Systematic or multiple reproduction, distribution to multiple locations via electronic or other means, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper is prohibited and is subject to penalties under law.