A Method for Reducing the Effect of Surface Contamination Layers in Reflection Diagnostics of Graphene-like 2D Materials

Abstract

The values of the published dielectric constants of graphene determined on the basis of optical diagnostics methods differ significantly from each other. This is due, in particular, to contaminating layers on the surface of graphene or between the substrate and the graphene layer, the parameters of which are not generally known and which, therefore, are difficult to take into account. In this work, it is shown how to integrate ellipsometric and reflectance measurements so that the influence of contaminating layers on the determination of dielectric constants of graphene-like 2D materials is minimal or practically absent at all. The inversion problem is solved analytically within the long-wavelength approximation. The equations for determining the dielectric constants of graphene have only one definite solution and do not need the knowledge of the initial guesses. A thorough analysis has been made of the dependence of the method error on the parameters of the structure under study, the wavelength and angle of incidence of optical radiation.