Interference effect on Raman spectrum of graphene on SiO2/Si

The intensity ratio between two major Raman bands in graphene is one of the most important pieces of information for physics of graphene and has been believed to represent various intrinsic properties of graphene without critical assessment of extrinsic effects. We report a micro-Raman spectroscopy study on the Raman intensity ratio of the 2D band to the G Raman band of graphene varying the thickness of dielectric layers (SiO2) underneath it. The ratio is shown to change by almost 370% when the thickness is varied by 60%. The large variation in the ratio is well explained by theoretical calculations considering multiple Raman scattering events at the interfaces. Our analysis shows that the interference effect is critical in extracting the intrinsic 2D to G intensity ratio and therefore must be taken into account in extracting various physical properties of graphene from Raman measurements.