Optical conductivity measurement of chemically-doped graphene via terahertz time-domain spectroscopy

We study optical conductivity of CVD-grown graphene depending on chemical doping conditions using terahertz time-domain spectroscopy. Varying the exposure duration of FeCl 3 solution, used for copper etching in the transfer process, allows graphene to have various carrier densities. According to terahertz transmission measurement, we confirm that the terahertz conductivity of graphene tends to increase with the exposure time to the chemical solution. It supports that Fermi level of graphene film can be controlled by chemical doping based on cooper etchants.