Counting graphene layers based on the light-shielding effect of Raman scattering from a substrate

We present a method for determining the number of stacked layers in graphene by exploiting its light-shielding effect. If a substrate supporting graphene has Raman-active modes, its Raman bands can be obtained simultaneously with the G and G′ bands of graphene. The Raman intensities from the substrate decrease with increasing the number of graphene layers because of the low opacity of graphene for visible light. The relationship between the number of graphene layers n and the relative intensities In,h/I0,h from the substrate can be represented by In,h/I0,h = 0.9772n, on the basis of the optical transmittance of visible light for single-layer graphene. The method is simple, convenient, highly accurate, and can be used to count beyond six layers up to 30 layers.