Twist Angle mapping in layered WS2 by Polarization-Resolved Second Harmonic Generation

TL;DR

This paper demonstrates a polarization-resolved second harmonic generation imaging technique for high-resolution, large-area mapping of twist angles in stacked WS2 layers, enabling detailed characterization of 2D material heterostructures.

Contribution

The study introduces a novel P-SHG imaging method combining intensity and polarization data for precise twist angle mapping in layered TMDs.

Findings

Effective large-area twist angle mapping in WS2 layers.

Ability to image individual layers at specific twist angles.

High accuracy in pixel-by-pixel twist angle determination.

Abstract

Stacked atomically thin transition metal dichalcogenides (TMDs) exhibit fundamentally new physical properties compared to those of the individual layers. The twist angle between the layers plays a crucial role in tuning these properties. Having a tool that provides highresolution, large area mapping of the twist angle, would be of great importance in the characterization of such 2D structures. Here we use polarization-resolved second harmonic generation (P-SHG) imaging microscopy to rapidly map the twist angle in large areas of overlapping WS2 stacked layers. The robustness of our methodology lies in the combination of both intensity and polarization measurements of SHG in the overlapping region. This allows the accurate measurement and consequent pixel-by-pixel mapping of the twist angle in this area. For the specific case of 30o twist angle, P-SHG enables imaging of individual layers.