Etchant-based chemical doping of large-area graphene and the optical characterization via terahertz time-domain spectroscopy

We investigate simple chemical doping process and the optical characterization of large-area graphene. The large-area graphene is grown on copper foil by chemical vapor deposition method, where carrier density is varied by exposure duration within FeCl 3 solution after complete etching of copper. Using terahertz time-domain spectroscopy, we obtain terahertz conductivity with different exposure duration. We confirm that the longer exposure time, the higher conductivity, which results from p -type doping due to copper etchant. The result implies that varying etching time during transfer process enables distinguished Fermi levels in graphene sheet, essential for simple fabrication of doping-level-controlled graphene sample.