Charge Dynamics and Electronic Structures of Monolayer MoS₂Films Grown by Chemical Vapor Deposition

THz absorption and spectroscopic ellipsometry were used to investigate the charge dynamics and electronic structures of chemical-vapor-deposited monolayer MoS 2 films. THz conductivity displays a coherent response of itinerant charge carriers at zero frequency. Drude plasma frequency (∼7 THz) decreases with decreasing temperature while carrier relaxation time (∼26 fs) is almost temperature independent. The absorption spectrum of monolayer MoS 2 shows a direct 1.95 eV band gap and charge transfer excitations that are ∼0.2 eV higher than those of the bulk counterpart. The ground-state exciton binding energy is found to be about 0.48 eV.