THz time-domain spectroscopy characterization of carbon nanostructures

Abstract

Carbon nanotubes and graphene show potential in commercial application due to their extreme mechanical, and electrical properties. This work deals with analysis of single-walled carbon nanotubes (SWCNT with a chiral index of 7,5) wrapped in poly 9, 9-di-n-octylfluorenyl-2, 7-diyl (PFO) in a toluene solution, in a thin film sample and graphene flakes embedded in PET ((polyethylene terephthalate) with 1 % graphene content). In this study, a nondestructive THz time-domain spectroscopy (THz-TDS) method utilizing the emission and detection of coherent and linearly polarized THz waves were used for characterization of the index of refraction, the optical absorption, electric permittivity and conductivity of mentioned forms of carbon in wide range 0.1 ÷ 3.5 THz frequencies. Our experimental results show that the most intensive optical absorption in SWCNT liquid and thin film samples as well as in graphene flakes appears to be at frequencies higher than 2 THz and varies in different forms of carbon bonding. Our calculated the real and imaginary parts of the electric conductivity and their dependences on frequency of incident THz wave can be also explained by different carbon bonding in our tested samples. All experimental results are presented and discussed.