In this work, a study of resonance effects in the Raman spectra of twisted bilayer graphene (tBLG) is presented. The analysis takes into account the effect of the mismatch angle $\theta$ between the two layers, and also of the excitation laser energy on the frequency, linewidth, and intensity of the main Raman features, namely the rotationally induced $R$ band, the $G$ band, and the second-order $G^{\prime }$ (or $2D$) band. The resonance effects are explained based on the $\theta$ dependence of the tBLG electronic structure, as calculated by ab initio methodologies. The twist angle $\theta$ also defines the observation of a “$D$-like” band which obeys the double-resonance process, but relies on the superlattice along with long-range defects in order to fulfill momentum conservation. The study was possible due to the development of a route to produce and identify rotationally stacked bilayer graphene by means of atomic force microscopy (AFM).

• Received 1 March 2013

DOI:https://doi.org/10.1103/PhysRevB.88.085401