Complex optical conductivity of graphene measured by ultra-broadband THz time-domain spectroscopic ellipsometry

Carrier dynamics in a single-layered graphene has been studied by reflection-type THz time-domain spectroscopic ellipsometry (THz-TDSE). THz-TDSE determines the ellipsometric parameter ρ=r_p/r_s by measuring the p- and s-polarized THz waveforms after the reflection form sample. We successfully obtained the frequency-dependent complex sheet conductivity of monolayer graphene from 0.3 to 20 THz. By fitting with Drude model, the sheet resistance, sheet carrier density and mobility of graphene were estimated. THz-TDSE can be a novel tool for the non-contact and non-destructive characterization of the carrier transport property in graphene samples.