Microwave to terahertz characterization of carbon nanotube materials

Microwave to THz characterizations of standalone MWNT paper and SWNT and few-layer-graphene thin films on glass substrates are presented. The MWNT paper is treated as an effective medium and its complex permittivity and permeability are extracted from both transmission and reflection measurements done in microwave and THz regimes. The results from these two different frequency ranges agree well. Due to its much smaller thickness compared to the characterization wavelength, the SWNT and graphene films are treated as a boundary condition with finite surface conductivity at the air-substrate interface. Their surface conductivities are extracted from the characterization, and show good consistency with reported values in literature at DC and optical frequency ranges. This surface conductivity characterization method is also applied as a verification approach for a potential metallic SWNT removing process using microwave irradiation induced current.