Figure 15.3 — Raman spectra of carbon tetrachloride and graphene Figure 15.3 — Raman spectra of carbon tetrachloride and graphene. (a) Stokes and anti-Stokes Raman spectra of carbon tetrachloride molecules (CCl4) at room temperature excited by an argon ion laser at 514.5 nm. (b) Raman spectrum of an optically trapped graphene flake with 633 nm trapping and excitation wavelength. Besides the G and 2D peaks, typical of carbon structures, it features significant peaks at D, D’ and the combination mode D+D’. Although the D peak is generally associated with structural defects, in this case it is related to the edges of the trapped sub-micrometre flakes (Ferrari and Basko, 2013).Figure (a) is reprinted from Gucciardi et al. (2007) with kind permission from Springer Science and Business Media.Figure (b) is reprinted with permission from Maragò et al., ACS Nano 4, 7515–7523. Copyright (2010) American Chemical Society.