Optical conductivity of single layer graphene from experimental measurements and theoretical calculations

Abstract

With the fast growing research and applications of graphene in photonics, understanding its properties and their correlation over broad spectral range is essential. The study presented herein is an analysis of optical conductivity and absorbance of chemical vapour deposition (CVD) single layer graphene (SLG). Optical transmittance measurements of the SLG module were performed over photon energy range from nearultraviolet (NUV, 300 nm) to near-infrared (NIR, 2500 nm) spectral regions. For photon wavelengths between 380 and 750 nm, graphene yielded an average transmittance of 97.6% with a maximum transparence peak of 98.3% at 710 nm wavelength. These results compares favorably with the reported theoretical T( )  of 97.7%. Arguably, the numerical value of optical conductivity,  for SLG (expressed in terms of universal optical conductivity,  o ), equates to the absorbance (in units of  ). Within the visible region, /   o = 1.04, which shows a close approximation of  to  o . However, within the NIR and NUV, this approximation of  disappears, where its value decreases sharply with energy in the NUV region. This behavior of the optical conductivity approximating to the universal optical conductivity may be explained in terms of the contributions from inter-band and intra-band transitions.