Weak Distance Dependence of Hot-Electron-Transfer Rates at the Interface between Monolayer MoS₂ and Gold

Abstract

Electron transport across the transition metal dichalcogenide (TMD)-metal interface plays an important role in determining the performance of TMD-based optoelectronic devices. However, the robustness of this process against structural heterogeneities remains unexplored, to the best of our knowledge. Here, we employ a combination of time-resolved photoemission electron microscopy (TR-PEEM) and atomic force microscopy to investigate the spatially resolved hotelectron transfer dynamics at the monolayer (1L) MoS2/Au interface. A spatially heterogeneous distribution of 1L-MoS2/Au gap distances, along with the sub-80-nm spatial-and sub-60-fs temporal resolution of TR-PEEM, permits the simultaneous measurement of electron transfer rates across a range of 1L-MoS2/Au distances. These decay exponentially as a function of distance, with an attenuation coefficient 𝛽 ~ 0.06 ± 0.01 Å -1 , comparable to molecular wires.Ab Initio simulations suggest that surface plasmon-like states mediate hot-electron transfer, hence accounting for its weak distance dependence. The weak distance dependence of the interfacial hot-electron transfer rate indicates that this process is insensitive to distance fluctuations at TMD-metal interfaces, thus motivating the further exploration of optoelectronic devices based on hot carriers.

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