Weak Distance Dependence of Hot-Electron-Transfer Rates at the Interface between Monolayer MoS<sub>2</sub> and Gold
Ce Xu, Hui Wen Yong, Jinlu He, Run Long, Alisson R. Cadore, Ioannis Paradisanos, Anna K. Ott, Giancarlo Soavi, Sefaattin Tongay, Giulio Cerullo, Andrea C. Ferrari, Oleg V. Prezhdo, Zhi-Heng Loh
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 hot-electron-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 the TMD/metal interface, thus motivating further exploration of optoelectronic devices based on hot carriers.