Gate-controlled nonlinear conductivity of Dirac fermion in graphene field-effect transistors measured by terahertz time-domain spectroscopy.
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 was modulated by electrostatic and chemical doping. The measured frequency-dependent optical sheet conductivity of graphene shows electron-density-dependence characteristics, which can be understood by a simple Drude model. In a low carrier density regime, the optical sheet conductivity of graphene is constant regardless of the applied gate voltage, but in a high carrier density regime, it has nonlinear behavior with respect to the applied gate voltage. Chemical doping using viologen was found to be efficient in controlling the equilibrium Fermi level without sacrificing the unique carrier dynamics of graphene.
Department of Physics, University of Seoul, Seoul 130-743, Korea.
Inhee
I
Maeng
Seongchu
S
Lim
Seung Jin
SJ
Chae
Young Hee
YH
Lee
Hyunyong
H
Choi
Joo-Hiuk
JH
Son
D004553:Electric Conductivity; D005740:Gases / Q000737:chemistry; D006108:Graphite / Q000737:chemistry*; D010316:Particle Size; D013499:Surface Properties; D055068:Terahertz Spectroscopy; D013997:Time Factors; D014173:Transistors, Electronic; D014835:Volatilization
D005740:Gases; D006108:Graphite