New Insight into the Characterization of Graphene Oxide and Reduced Graphene Oxide Monolayer Flakes on Si-Based Substrates by Optical Microscopy and Raman Spectroscopy

Abstract

Graphene oxide (GO) and reduced GO (RGO) have attracted interest as economical alternatives for pristine graphene with controllable properties spanning their applications in many fields. Abundant lattice defects present in GO and RGO have made their physical and chemical properties largely diverse from that of pristine graphene. This makes their identification and characterization ambiguous as the rules applied for pristine graphene may not be practical for GO and RGO. Here, we report a new insight into the characterization of GO and thermally reduced GO monolayer flakes deposited on different commonly used Si-based substrates by Raman spectroscopy along with optical visualization to address this uncertainty. It was found that the dielectric substrates with a lower reflectance in the visible range give a better optical contrast under normal white light illumination and intense Raman signals owing to the multiple reflection and interference at the interfaces of the multilayer system. Accordingly, a Si substrate with a 90 nm SiO2 layer gives the highest IG′/IG ratio along with a better optical visibility for monolayer RGO flakes.