Gate-Controlled Nonlinear Conductivity of Dirac Fermion in Graphene Field-Effect Transistors Measured by Terahertz Time-Domain Spectroscopy

• DOI: 10.1021/nl202442b
• Publication Date: 2012-01-03T18:18:41Z
• Authors: Inhee Maeng; Seongchu Lim; Seung Jin Chae; Young Hee Lee; Hyunyong Choi; Joo-Hiuk Son
• Keywords: Optical conductivity

We present terahertz spectroscopic measurements of Dirac fermion dynamics from a large-scale graphene that was grown by chemical vapor deposition and on which carrier density modulated electrostatic doping. The measured frequency-dependent optical sheet conductivity shows electron-density-dependence characteristics, can be understood simple Drude model. In low regime, the is constant regardless applied gate voltage, but in high it has nonlinear behavior with respect to voltage. Chemical doping using viologen found efficient controlling equilibrium Fermi level without sacrificing unique graphene.