title: Intercalation of few-layer graphite flakes with FeCl3: Raman determination of Fermi level, layer by layer decoupling, and stability.
abstract: We use anhydrous ferric chloride (FeCl(3)) to intercalate graphite flakes consisting of 2-4 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 heavily doped monolayer graphene upshifts to ∼1627 cm(-1). The 2-4 layer ICs have similar upshifts, and a Lorentzian line shape for the 2D band, indicating that each layer behaves as a decoupled heavily doped monolayer. By performing Raman measurements 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, multiwavelength Raman spectroscopy allows a direct measurement of the Fermi level, complementary to that derived by performing measurements at fixed excitation energy significantly higher than the doping level. This allows us to estimate a Fermi level shift of up to ∼0.9 eV. These ICs are thus ideal test-beds for the physical and chemical properties of heavily doped graphenes.
authors: State Key Laboratory for Superlattices and Microstructures, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China.
authors: Weijie
authors: W
authors: Zhao
authors: Ping Heng
authors: PH
authors: Tan
authors: Jian
authors: J
authors: Liu
authors: Andrea C
authors: AC
authors: Ferrari