Quantum plasmonic imaging of 2D transition metal dichalcogenides

Two-dimensional (2D) transition metal dichalcogenides (TMDs) are of particular interest due to their unique optoelectronic properties. Nano-optical imaging techniques such as tip-enhanced Raman spectroscopy (TERS) and tip-enhanced photoluminescence (TEPL) are useful tools for investigating the nanoscale properties of materials below the diffraction limit. We investigated the topography and optical properties of monolayer TMDs using atomic force microscopy (AFM), TERS, and TEPL. Near-field TEPL and TERS signals have been found to be successful in identifying distinct crystalline boundaries with higher spatial resolution compared to far-field imaging. Subwavelength optical characterization techniques are necessary to study nanoscale phenomena such as the lateral heterojunctions of 2D materials. We also performed tip-sample distance dependence experiments and observed quantum plasmonic effects. Specifically, manipulating the plasmonic tip location results in nano-optical imaging capabilities and plasmon-induced hot-electron injection. As a result, there is significant potential for applying quantum plasmonic effects to nanodevices with tunable photoresponse.