Figure 4.

(a) The measured refractive index n and extinction coefficient k of CVD graphene on three different substrates. For the tabular data, see Appendix A Table A1. (b) Comparison of the measured optical constants (red lines) and some previous results for CVD graphene obtained under the assumption of the presence of nanometer-thick layers of water in the ellipsometric model (cyan and magenta lines). Solid, n, and dashed, k, lines. The data of Ochoa-Martinez and Castriota are adopted from refs. [28,31], respectively.