Hyunyong Choi

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.

Exciton dynamics in atomically thin MoS2: Interexcitonic interaction and broadening kinetics

We report ultrafast pump-probe spectroscopy examining exciton dynamics in atomically thin MoS

Controllable synthesis of molybdenum tungsten disulfide alloy for vertically composition-controlled multilayer

{}_{2}

Rotation‐Misfit‐Free Heteroepitaxial Stacking and Stitching Growth of Hexagonal Transition‐Metal Dichalcogenide Monolayers by Nucleation Kinetics Controls

. Spectrally and temporally resolved measurements are performed to investigate the interaction dynamics of two important direct-gap excitons (

Interlayer orientation-dependent light absorption and emission in monolayer semiconductor stacks

A

High-field terahertz response of graphene

and

Unusually efficient photocurrent extraction in monolayer van der Waals heterostructure by tunnelling through discretized barriers

B

Ultrafast refractive index control of a terahertz graphene metamaterial

) and their associated broadening kinetics. The two excitons show strongly correlated interexcitonic dynamic, in which the transient blue-shifted excitonic absorption originates from the internal A-B excitonic interaction. The observed complex spectral response is determined by the exciton collision-induced linewidth broadening; the broadening of the

Solvent-Assisted Gel Printing for Micropatterning Thin Organic–Inorganic Hybrid Perovskite Films

B

Ultra-high modulation depth exceeding 2,400% in optically controlled topological surface plasmons.

-exciton linewidth in turn lowers the peak spectral amplitude of the