In Situ Optical Tracking of Electroablation in Two-Dimensional Transition-Metal Dichalcogenides.

Two-dimensional (2D) transition-metal dichalcogenides (TMDs) are a unique class of 2D materials possessing unique optoelectronic properties when exfoliated into mono- and few-layer sheets. Recently, electroablation (EA) has become of interest as a promising synthesis method for single-layer sheets of TMDs. Here, we introduce spectroelectrochemical micro-extinction spectroscopy (SE-MExS) as a high-throughput technique to study electrochemical thinning of TMDs as it occurs. This approach enables the parallel use of spectroscopy and imaging to nondestructively characterize 2D materials in situ. We unravel optoelectronics of the TMDs by observing changes in optical properties during EA. We find that the EA process for MoS, WS, MoSe, and WSe occurs edge first, generating high density of edge sites. Our results show that stable monolayers of MoS, WS, and MoSe can be synthesized from bulk precursors by the EA process, while conversely, no WSe remains postablation.