G phonon linewidth and phonon-phonon interaction in p-type doped CVD graphene crystals

Abstract

We employed conventional and time-resolved Raman spectroscopy to study the effects of electron-phonon and phonon-phonon interactions on the linewidth of the G phonon in both unintentionally and intentionally doped polycrystalline chemical vapor deposited (CVD) graphene samples. We directly measured the G phonon lifetime, observing a ≈14% decrease with doping up to EF = 270 meV. The anticipated reduction of G phonon linewidth due to a decrement in electron-phonon contribution deviates from first principles calculations. CVD samples exhibit a ≈30% decrease in the electron-phonon coupling constant, λΓ(EF = 0), compared to exfoliated graphene samples. Additionally, phonon-defect scattering makes a significant contribution to the G band linewidth in CVD graphene samples, owing to their lower crystal quality compared to exfoliated graphene.