Investigating carrier dynamics in TMD monolayer heterostructures for different stacking configurations (Invited Paper)

Investigations of heterostructures of transition metal dichalcogenides (TMDs) at the microscopic level have been carried out using a variety of methods. However, the charge carrier dynamics in heterostructures composed of different types of TMDs remain unclear. In this study, we investigate three different TMDs heterostructures using Raman spectroscopy and ultrafast pump-probe microscopy (UPPM) to gain a better understanding of the carrier dynamics taking place. The heterostructures are consisting of MoS₂ and WS₂ monolayers arranged in a vertical stacking configuration (MoS₂-MoS₂/WS₂), a lateral connection (MoS₂-WS₂) and a combination of both, resulting in a lateral connection with an additional layer on top (MoS₂-MoS₂/WS₂-WS₂). All three samples are grown by chemical vapor deposition (CVD) in a two-step process. The Raman characterization validates the configurations and examines the quality of the layers and interfaces. UPPM is performed using 3.1eV for pumping and 1.55eV for probing the sample at different delay times. The transmission through the sample is investigated by studying the behavior during the excitation and recombination processes in all three samples. Charge carrier dynamics are analyzed, considering the effect of defects in relation to the layer structure. Additionally, we briefly discuss the challenges arising from a high number of defects and the layer thickness. Our findings help to provide new insights into the carrier dynamics and the optimization of TMD heterostructures for potential applications in electronic and optoelectronic devices.