Visibility of few-layer graphene oxide under modified light using bandpass filters

In this study, a method of evaluating and enhancing the visibility of graphene oxide on dielectric films was investigated. To evaluate the visibility in a multiwavelength range, we have suggested two parameters, the red, green, and blue (RGB) contrast and the RGB difference. By using these two parameters, researchers can easily determine whether the visibility comes from the color difference or from the intensity difference between the material and substrate. A high contrast image can be acquired by filtering the light source with color filters. It is predicted that the visibility of the graphene oxide monolayer may be three times as high under normal halogen light. By measurement, the visibility of graphene oxide on 70 nm Si₃N₄/Si increased 2.67±0.13 times under a green-filtered light. The calculated colors of graphene oxide from the RGB parameter can be effectively used to estimate the graphene oxide layer thickness and effective dielectric film thickness for high visibility graphene oxide.