Resonance Raman spectroscopy of G-line and folded phonons in twisted bilayer graphene with large rotation angles

We report the synthesis and systematic Raman study of twisted bilayer graphene (tBLG) with rotation angles from below 10 degrees to nearly 30 degrees. Chemical vapor deposition was used to grow hexagon-shaped tBLG with a rotation angle that can be conveniently determined by relative edge misalignment. Rotation dependent G-line resonances and folded phonons were observed by selecting suitable energies of excitation lasers. The observed phonon frequencies of the tBLG superlattices agree well with our ab initio calculation. (C) 2013 AIP Publishing LLC.