Rapid and non-destructive identification of graphene oxide thickness using white light contrast spectroscopy Original Research Article

By white light contrast spectroscopy, we have successfully identified number of graphene oxide (GO) layers (⩽10 layers) and obtained a new refractive index of GO sheets (⩽10 layers) of nGO = 1.2–0.24i. For few layers (⩽10 layers) GO sheets, both the contrast at ∼580 nm wavelength and the Raman intensity of G band linearly increase with the increase of the layer numbers. However, due to the laser induced heating effects and the requirement of a reference Raman spectrum in Raman spectroscopy measurements, contrast spectroscopy is non-destructive and more efficient. Simulations based on the Fresnel’s equations agree well with evolution of the contrast and G band intensity as a function of number of layers. The precise refractive index of GO obtained in this work can be widely used in further study of GO. Therefore, our experimental contrast values can be directly used as a standard to identify the thickness of GO on Si substrate with 300 nm SiO2 capping layer, which paves a novelty way towards future fundamental research and applications of graphene-based materials.