Evaluation of local exciton dynamics of single-layer WS₂ using time-resolved multi-probe STM

Abstract

Transition metal dichalcogenide (TMDCs) two-dimensional semiconductors have attracted much attention in recent years as ultra-thin device candidates due to their two-dimensional optoelectronic properties. In this study, we measured exciton dynamics in the wrinkled structure in WS₂ prepared by chemical vapor deposition on a SiO₂ / Si substrate by combining a pump-probe optical system with a multi-probe STM. As a result of fitting the time-resolved spectrum with a single-component exponential function, the time constant was larger at the top than at the bottom. This suggests that the EEA process of excitons may be locally activated at the bottom due to the fluctuation of the potential derived from the substrate.