We have studied the spatial variation in carrier dynamics in ReS2 flakes using ultrafast pump-probe microscopy. In contrast to other highly symmetric TMDCs like MoS2 and WS2, ReS2 remains a direct bandgap semiconductor regardless of the number of layers due to its low-symmetry distorted 1T crystal structure. This low symmetry also gives rise to anisotropic optical and electronic properties. We have used polarization-resolved pump-probe microscopy to investigate how structural features, such as thickness and defects, influence the carrier dynamics in ReS2 nanoflakes. In these experiments, a localized region on a single nanoflake is excited with a linearly polarized 440 nm femtosecond laser pulse focused through a microscope objective. A second 880 nm laser pulse with variable arrival time and polarization probes how the excitation evolves in time. Carrier recombination dynamics were studied by measuring the difference in the transmission of the 880 nm probe as its time delay increases with respect to the initial 440 nm pump. At fixed time delays, changes due to polarization were resolved by rotating the probe polarization. Optical images, constructed by moving the sample stage at a fixed time delay and polarization, were then compared to atomic force microscopy (AFM) height profiles to correlate carrier dynamics with structural features.

Ultrafast pump-probe microscopy investigation of carrier dynamics in anisotropic ReS2 nanoflakes

ACS Fall 2020 Virtual Meeting

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.