Reliably Counting Atomic Planes of Few-Layer Graphene (n>4)

We demonstrate a reliable technique for counting atomic planes (n) of few-layer graphene (FLG) on SiO2/Si substrates by Raman spectroscopy. Our approach is based on measuring the ratio of the integrated intensity of the G graphene peak and the optical phonon peak of Si, I(G)/I(Si), and is particularly useful in the range n>4 where few methods exist. We compare our results with atomic force microscopy (AFM) measurements and Fresnel equation calculations. Lastly, we apply our method to unambiguously identify n of FLG devices and find that the mobility (~2000 cm2 V-1 s-1) is independent of layer thickness for n>4.