  We report an experimental Raman study of few-layer graphene after chemical
doping achieved by a plasma process in CHF$_3$ gas. A systematic reduction of
both the splitting and the area of the 2D band is observed with increasing the
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 resonant
Raman process.
