Charge Dynamics and Electronic Structures of Monolayer MoS2 Films 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 MoS2 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 MoS2 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.