Charge Effects\nand Electron Phonon Coupling in Potassium-Doped\nGraphene

Herewith, we propose a comprehensive study of the vibrational\nresponse\nof chemical doping of free-standing graphene (Gr). Complementary insights\non the increased metallicity have been demonstrated by the emerging\nplasmon excitation in the upper Dirac cone, observed by inelastic\nelectron scattering and core-level photoemission. The electron migration\nin the π* upper Dirac band unveils an electron–phonon\ncoupling of contaminant-free K-doped Gr, as evidenced by advanced\nmicro-Raman spectroscopy in ultrahigh vacuum ambient. The vibrational\nresponse of potassium-doped Gr correlated with the charge injected\nin the upper Dirac cone, and the Fermi level shift unravel a notable\nelectron–phonon coupling, which is stronger than that observed\nfor gate voltage-doped Gr.