Two-dimensional semiconductors (2DSCs) such as the transition metal dichalcogenides are promising materials for a variety of optoelectronic applications. While the fabrication of 2DSCs with thicknesses down to the monolayer limit has been demonstrated through a variety of routes, an improved understanding of carrier transport within these materials is needed to guide the rational design of future devices. In this presentation, new approaches to visualizing carrier transport within 2DSCs are described. These methods utilize a combination of optical and electrochemical probes to locally generate carriers and probe their concentration at a spatially displaced electrolyte interface defined by a pipet-based probe. This approach, Carrier Generation-Tip Collection Scanning Electrochemical Cell Microscopy (CG-TC SECCM), is capable of directly probing transport along well-defined, µm-scale paths within 2DSCs, which allows the impact of individual structural defects on transport to be rigorously examined. The utility of this approach is demonstrated through studies of transport in a series of transition metal dichalcogenide (TMD) structures. CG-TC SECCM studies carried out in thick (&gt;10 nm) TMD structures allow bulk in-plane and out-of-plane carrier diffusion lengths to be evaluated and recombination at individual step-edge defects to be directly interrogated. Studies carried out within thinner TMD structures reveal how carrier transport varies as thicknesses approach the monolayer limit. Together, the presented work not only provides valuable new insights into carrier transport within 2DSCs, but also demonstrates electrochemical imaging to be a powerful, yet underutilized approach for visualizing solid-state processes in semiconducting materials.

Electrochemical methods for visualizing carrier transport and recombination in 2D semiconductors

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.