Rapid Determination of the Thickness of Graphene Using the Ratio of Color Difference

An optical method was proposed, based on the ratio of color difference, to identify the thickness of graphene on dielectric/Si substrates. The effect of light source on the color difference of graphene sheets has been investigated. The result shows that for the number of graphene layers N <= 10, the ratio between the color differences of N- and single-layer graphene remains almost unchanged under different light sources. It suggests that one can accurately identify the number of graphene layers by comparing the experimental and theoretical ratio of color difference of graphene without knowing the illuminant's parameters. The method is rapid, nondestructive, and illuminant independent and needs only an optical image to determine the thickness of graphene sheets.