Characterization Techniques for Graphene-Based Materials

Graphene bearing 2D (dimensional) layer of carbon atoms bonded in sp2 hybridized state are only 1 atomic-scale thick. However, the graphene can be extended along the horizontal dimension. The alternate double bonds leading to perfect conjugation with sp2 hybridization are exhibited in the hexagonal structure (honeycomb) of graphene. Theoretically and experimentally, the thicknesses of graphene have been determined and are in the nano-meter range. The extraordinary mechanical and electrical properties exhibited by such a 2D material have inspired scientists for device fabrication methodologies that can shift the synthesis from lab scale to large scale. It is considered the strongest material on earth, almost 100 times stronger (i.e., strength) than the best steel. Since graphene is only 1 atomic-scale thick and transparent, the characterization of graphene is complex but essential. The thickness down to one atomic layer in graphene can be identified by the light interference causing color contrast. Thus, optical microscopy-based methods enable the identification of graphene or its derivatives; on the other hand, Raman spectroscopy, which is sensitive to molecular bonding and geometric structure, is commonly employed for the quality determination of graphene-based materials. In this chapter, various characterization techniques are discussed, enabling the characterization of graphene and graphene-based materials (GBMs).