Variable angle spectroscopic ellipsometry characterization of graphene oxide and reduced graphene oxide thin films

Recently, the optical properties of Graphene Oxide (GO) and Reduced Graphene Oxide (RGO) films have been determined in the ultraviolet and visible spectral range. However, the accurate optical properties in the extended near-infrared and mid-infrared range have not been published yet. In this work, we report a Variable Angle Spectroscopic Ellipsometry (VASE) characterization of GO thin films dip-coated on SiO2/Si substrates and thermally reduced GO thin films in the [0.38-4.1] eV photon energy range. Moreover, the optical properties of RGO stabilized with poly(sodium 4-styrenesulfonate) (PSS) films dip-coated on SiO2/Si substrates are studied in the same range for the first time. The Lorentz optical models fit well the experimental data. In addition, the morphological properties of the samples were investigated by Scanning Electron Microscopy (SEM) analysis.