Optical pump-probe studies of carrier dynamics in few-layer MoS2

Femtosecond optical pump-probe technique is used to study charge carrier dynamics in few-layer MoS2 samples fabricated by mechanical exfoliation. An ultrafast pump pulse excites carriers and differential reflection of a probe pulse tuned to an excitonic resonance is detected. We find that the spectrum of the differential reflection signal is similar to the derivative of the resonance. The decay time of the signal is in the range of 150 to 400 ps, increasing with the probe wavelength. With a fixed probe wavelength, the signal magnitude is proportional to the pump fluence, while the decay time is independent of it.