Ultrafast Charge Transfer Dynamics at the MoS${}_2$/Au Interface Observed via Optical Spectroscopy under Ambient Conditions

Abstract

To take advantage of the exceptional properties of atomically thin transition metal dichalcogenides (TMDC) for advanced devices and catalysts, integration with metallic surfaces is an efficacious approach for facilitating charge carrier injection and extraction from TMDC monolayers. Light-matter interactions predominantly occur at the K point in TMDC monolayers, making the charge carrier dynamics at this point essential for their optimal performance. However, direct access to and comprehensive understanding of the charge carrier dynamics at the K point of TMDC monolayer on a metal substrate remains challenging. In this study, we employed azimuth- and polarization-dependent final-state sum frequency generation (FS-SFG) spectroscopy to investigate the ultrafast dynamics of charge transfer at the K point of a MoS${}_2$ monolayer interfaced with an Au substrate. We observed an ultrafast injection (sub-20 fs) of photoexcited hot electrons from the Au substrate to the conduction band minimum (CBM) of the MoS${}_2$ monolayer. Subsequently, driven by an internal electric field induced by charge redistribution, injected hot electrons in MoS${}_2$ experience a relaxation and fast return ($\sim 2$ ps) from the CBM and a trap state mediated slow return ($\sim 60$ ps) process. The direct optical observation of the full electron dynamics at the K point of MoS${}_2$ monolayer in ambient conditions provides valuable insights into the mechanisms of charge carrier transfer across the TMDC-metal interface, informing the design of advanced TMDC-based devices with enhanced charge transfer rates.

16 pages, 3 figures and supplemental material

References in corpus (21)

• Coupled spin and valley physics in monolayers of MoS2 and other group-VI dichalcogenides
• Excitons in atomically thin transition metal dichalcogenides
• Exciton physics and device application of two-dimensional transition metal dichalcogenide semiconductors
• Observation of Intense Second Harmonic Generation from MoS${}_2$ Atomic Crystals
• Second harmonic microscopy of monolayer MoS2
• Ultrafast Dynamics of Defect-Assisted Electron-Hole Recombination in Monolayer MoS2
• Directly visualizing the momentum forbidden dark excitons and their dynamics in atomically thin semiconductors
• Trion Formation Dynamics in Monolayer Transition Metal Dichalcogenides
• Large spin-orbit splitting of deep in-gap defect states of engineered sulfur vacancies in monolayer WS2
• Single-layer MoS${}_2$ on Au(111): band gap renormalization and substrate interaction
• Observation of Ultrafast Free Carrier Dynamics in Single Layer MoS${}_2$
• The ultrafast onset of exciton formation in 2D semiconductors
• UV/Ozone treatment to reduce metal-graphene contact resistance
• Momentum-resolved observation of exciton formation dynamics in monolayer WS${}_2$
• Direct measurement of key exciton properties: energy, dynamics and spatial distribution of the wave function
• Electron irradiation of metal contacts in monolayer MoS${}_2$ Field-Effect Transistors
• Ultrafast charge-transfer dynamics in twisted MoS${}_2$/WSe${}_2$ heterostructures
• Layer Dependent Interfacial Transport and Optoelectrical Properties of MoS2 on Ultra-flat Metals
• Microscopic understanding of ultrafast charge transfer in van-der-Waals heterostructures
• Time-dependent screening explains the ultrafast excitonic signal rise in 2D semiconductors
• Isolating the Nonlinear Optical Response of a MoS${}_2$ Monolayer under Extreme Screening of a Metal Substrate