On Estimating the G-peak shift in graphene Raman spectra

Resumo

The frequency shift of the Raman G peak of epitaxial graphene due to the interaction with a substrate described by effective bond force constant k is investigated using the model of two coupled oscillators. The relative G-peak shift is shown to be Δω(G)/ω(G) ∝ k/k_0g, where k0g is the bond-stretching force constant of single-layer graphene. Assuming k ∝ P and k ∝–T, where P and T are the pressure and temperature, and the k variation to be dominant, we qualitatively explain the experimental dependences of Δω(G) on P and T. The effect of the substrate on the G-peak broadening in epitaxial graphene is discussed.