  For the first time, we have observed the obvious triple G peak splitting of
ABA stacked trilayer graphene. The G peak splitting can be quantatively
understood through the different electron-phonon coupling strength of Ea', Eb'
and Ea" modes. In addition, the fluctuation of G peak position at different
sample locations can also be understood from the view of the varied interaction
strength among graphene layers of TLG, which is induced by nonuniform hole
doping at the microscopic level.
