Strain engineering in single-, bi- and tri-layer MoS2, MoSe2, WS2 and WSe2

TL;DR

This paper details methods for applying and measuring uniaxial strain on 2D transition metal dichalcogenides, analyzing how strain affects their optical and electronic properties across different layers and samples.

Contribution

It provides a comprehensive calibration technique for strain measurement and systematic analysis of strain effects on multiple TMD materials and layer configurations.

Findings

Strain significantly alters optical properties of TMDs.

Calibration method achieves high accuracy in strain quantification.

Variability among flakes affects strain response.

Abstract

Strain is a powerful tool to modify the optical properties of semiconducting transition metal dichalcogenides like MoS2, MoSe2, WS2 and WSe2. In this work we provide a thorough description of the technical details to perform uniaxial strain measurements on these two-dimensional semiconductors and we provide a straightforward calibration method to determine the amount of applied strain with high accuracy. We then employ reflectance spectroscopy to analyze the strain tunability of the electronic properties of single-, bi- and tri-layer MoS2, MoSe2, WS2 and WSe2. Finally, we quantify the flake-to-flake variability by analyzing 15 different single-layer MoS2 flakes.