Interlayer Coulomb interaction in twisted bilayer graphene nanofragments characterized by the vibrational mode of Gr+ band

Tip enhanced Raman spectra of AB-stacked bilayer graphene (BLG) and twisted bilayer graphene (TwBLG) nanofragments have been studied by using density functional theory. Different from a normal Raman spectrum of BLG, a unique Raman band G(r)(+) is observed in its tip enhanced Raman spectrum and assigned as a split of the G band. We attribute this split to the nonuniformity distribution of the charge on carbon atoms. Compared with BLG, the G(r)(+) band intensity of TwBLG is dramatically enhanced at a small twist angle and decreases with the angle increasing. Interlayer Coulomb interaction represented in the G(r)(+) mode of TwBLG matches well with the atom vibration strength distribution of the G(r)(+) band at different twist angles, and thereby the properties of the G(r)(+) band can be tuned by the twisted angle. The results may help to further understand the Raman spectra of TwBLG and provide deep insights for exploring vibrational modes of two-dimensional nanomaterials. Published under an exclusive license by AIP Publishing.

Automated summary

Tip enhanced Raman spectra of AB-stacked bilayer graphene and twisted bilayer graphene nanofragments have been studied. A unique Raman band G(r)(+) is observed and can be tuned by the twisted angle.