We report terahertz and infrared transmission measurements of a high-performance thermoelectric material containing tellurium nanowires in a conducting polymer poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) matrix. The DC electrical conductivity of the hybrid material (41 S/cm) is approximately one hundred times that of pure PEDOT:PSS and more than 400 times that of a film of pure tellurium nanowires, while the terahertz-frequency (THz) conductivity of PEDOT:PSS and the hybrid material are comparable at f ∼ 2THz. A frequency-dependent conductivity model indicates that the increased DC conductivity of the hybrid material results from an increase in the DC charge mobility rather than in the free charge density. We suggest that the increased DC conductivity of the hybrid material results from an increase in linkage between PEDOT domains by the tellurium nanowires.

Terahertz (THz) Faraday rotation measurements were performed to investigate carrier dynamics in p-type Chemical vapor deposition (CVD) graphene. We used static and time-resolved polarizationsensitive THz transmission measurements in a magnetic field to probe free carriers in GaAs, InP, and Graphene. Static measurements probe the equilibrium carrier density and momentum scattering rate. Time-resolved (optical pump/THz probe) measurements probe the change in these quantities following photoexcitation. In a typical CVD graphene sample, we found that 0.5 ps following photoexcitation with 1 Â 10 13 photons/cm 2 pulses at 800 nm the effective hole scattering time decreased from 37 fs to 34.5 fs, while the carrier concentration increased from 2.0 Â 10 12 cm À2 to 2.04 Â 10 12 cm À2 , leading to a transient decrease in the conductivity of the film. V C 2014 AIP Publishing LLC.

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