Optical properties of sunlight reduced graphene oxide using spectroscopic ellipsometry

This paper demonstrates the appropriateness of the Spectroscopic Ellipsometry (SE), a non destructive optical characterization technique in analyzing the optical properties of a few layers of reduced graphene oxide (RGO) in NIR-UV-Vis range of spectrum. The paper discusses the study of the optical properties of RGO sample prepared by exposing GO to natural sunlight. The Drude-Lorentz model is used to extract the optical constants of RGO from the ellipsometric measurement. This paper investigates how the optical parameters change due to the variations in the degree of reduction along with the presence of defects on RGO sheets. The result reveals that the refractive index (n) and the extinction coefficient (k) increase, with the increase in the level of reduction. The effect of the variations in structural defects and the presence of functional groups on the absorption coefficient are studied. The paper also discusses the sensitivity of ellipsometry in analyzing the variations in the dielectric constant due to presence of the residual oxygen moieties. Such detailed optical characterization of RGO samples has great potential application in deciding the best suitable reduction technique for developing specific optical device.