The evolution of Raman spectrum of graphene with the thickness of SiO2 capping layer on Si substrate

Abstract

In this paper, we have systematically studied the evolution of Raman spectrum of graphene with the thickness of SiO₂ capping layer on Si substrate. We find that, for both monolayer and bilayer graphenes, the intensities of D, G, and 2D bands, together with the intensity ratio of 2D to G Raman bands (I_2D/I_G), oscillate quasi-periodically with SiO₂ thickness increasing. The origin of the observed phenomena is theoretically analyzed. Our result shows that one must pay enough attention to the SiO₂ thickness when using the Raman footprints, especially the commonly used I_2D/I_G, to identify the graphene layers transferred onto SiO₂/Si substrate.