Theory of Strain-Induced Confinement in Transition Metal Dichalcogenide Monolayers

TL;DR

This paper presents a continuum-mechanical model to analyze strain-induced confinement in TMD monolayers on nanopillars, predicting band gap changes and electron escape rates consistent with experimental observations.

Contribution

It introduces a simple theoretical framework to estimate the topography and electronic effects of strain in TMD monolayers on nanopillars, linking geometry to optical properties.

Findings

Potential curvature is independent of nanopillar height.

Electron escape rate decreases with increasing nanopillar height.

Photon energy shifts predictably with nanopillar height.

Abstract

Recent experimental studies of out-of-plane straining geometries of transition metal dichalchogenide (TMD) monolayers have demonstrated sufficient band gap renormalisation for device application such as single photon emitters. Here, a simple continuum-mechanical plate-theory approach is used to estimate the topography of TMD monolayers layered atop nanopillar arrays. From such geometries, the induced conduction band potential and band gap renormalisation is given, demonstrating a curvature of the potential that is independent of the height of the deforming nanopillar. Additionally, with a semi-classical WKB approximation, the expected escape rate of electrons in the strain potential may be calculated as a function of the height of the deforming nanopillar. This approach is in accordance with experiment, supporting recent findings suggesting that increasing nanopillar height decreases the linewidth of the single photon emitters observed at the tip of the pillar, and predicting the shift in photon energy with nanopillar height for systems with consistent topography.