  We use anhydrous ferric chloride (FeCl3) to intercalate graphite flakes
consisting of 2 to 4 graphene layers and to dope graphene monolayers. The
intercalant, staging, stability and doping of the resulting intercalation
compounds (ICs) are characterized by Raman scattering. The G peak of monolayer
graphene heavily-doped by FeCl3 upshifts to~1627cm-1. 2-4 layer ICs have
similar upshifts, and a Lorentzian lineshape for the 2D band, indicating that
each layer behaves as a decoupled heavily doped monolayer. By performing Raman
measurement at different excitation energies we show that, for a given doping
level, the 2D peak can be suppressed by Pauli blocking for laser energy below
the doping level. Thus, multi-wavelength Raman spectroscopy allows a direct
evaluation of the Fermi level, complementary to that derived by Raman
measurements at excitation energies higher than the doping level. We estimate a
Fermi level shift of~0.9eV. These ICs are ideal test-beds for the physical and
chemical properties of heavily-doped graphenes.
