THz TDS study of several sp2 carbon materials: Graphite, needle coke and graphene oxides

Terahertz time-domain spectroscopy has been used to probe the properties of four carbon allotropes with a sequenced c-axis stacking order: single-layer reduced graphene oxide, few-layer graphene oxide, disordered needle coke and highly organized graphite. The results obtained demonstrate a very high sensitivity to the structural characteristics of the tested samples. The multi-layer materials show the same type of spectral response with strong variations in the attenuation in the whole terahertz band depending on their constructural organization. The single-layer sample shows a distinct response where conductive effects dominate. The results obtained are consistent with theoretical investigations using semi-empirical quantum chemistry methods.