Raman signature of electron-electron correlation in chemically doped few-layer graphene

We report an experimental Raman study of few-layer graphene after chemical doping achieved by a plasma process in CHF₃ gas. A systematic reduction of both the splitting and the area of the $2D$ band is observed with increasing doping level. Both effects can be ascribed to the electron-electron correlation, which, on the one hand, reduces the electron-phonon coupling strength and, on the other hand, affects the probability of the double-resonance Raman process.