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

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.