Raman scattering efficiency of graphene

Abstract

We determine the Raman scattering efficiency of the $G$ and $2D$ peaks in graphene. Three substrates are used: silicon covered with 300 or 90 nm oxide, and calcium fluoride (CaF${}_{2}$). On Si/SiO${}_{x}$, the areas of the $G$ and $2D$ peak show a strong dependence on the substrate due to interference effects, while on CaF${}_{2}$ no significant dependence is detected. Unintentional doping is reduced by placing graphene on CaF${}_{2}$. We determine the Raman scattering efficiency by comparison with the 322 cm${}^{\ensuremath{-}1}$ peak area of CaF${}_{2}$. At 2.41 eV, the Raman efficiency of the $G$ peak is $\ensuremath{\sim}200\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}5}$ m${}^{\ensuremath{-}1}$Sr${}^{\ensuremath{-}1}$, and changes with the excitation energy to the power of 4. The $2D$ Raman efficiency is at least one order of magnitude higher than that of the $G$ peak, with a different excitation energy dependence.