Nanometer-Scale Structure Property of WS2 Flakes by Nonlinear Optical Microscopy: Implications for Optical Frequency Converted Signals

Structural irregularities have attracted increasing attention in two-dimensional transition metal dichalcogenides (TMDCs), whose impacts on the electronic structure cannot be neglected. Here, nonlinear optical spectroscopy and microscopy are used to investigate these effects in tungsten disulfide (WS2) flakes based on the spatially resolved second harmonic generation (SHG) and room-temperature two-photon photoluminescence (2PPL). Notably, SHG intensity appears the strongest at these flake edges, which is anticorrelated with the room-temperature 2PPL response in monolayer WS2. This work provides a convenient method to probe the second-order susceptibility of TMDCs for the purpose of achieving a high optical frequency converted signal for nonlinear optical applications.

Automated summary

This study investigates the effects of structural irregularities on the electronic structure of two-dimensional transition metal dichalcogenides (TMDCs) using nonlinear optical spectroscopy and microscopy. It is found that the edges of tungsten disulfide (WS2) flakes exhibit the strongest second harmonic generation (SHG) intensity, which is anticorrelated with the room-temperature two-photon photoluminescence (2PPL) response in monolayer WS2. This work provides a convenient method to probe the second-order susceptibility of TMDCs and achieve high optical frequency converted signals for nonlinear optical applications.