Strain-Modulated Interlayer Charge and Energy Transfers in MoS2/WS2 Heterobilayer

TL;DR

This study demonstrates that applying hydrostatic pressure to MoS2/WS2 heterobilayers effectively modulates interlayer charge and energy transfer, offering a new mechanical control method for 2D excitonic devices.

Contribution

The paper introduces a novel pressure-based technique to control interlayer charge and energy transfer in 2D heterobilayers, supported by experimental and theoretical evidence.

Findings

Pressure enhances interlayer interaction in heterobilayers.

Photoluminescence indicates strong energy transfer at low pressure.

Charge transfer increases significantly at higher pressures.

Abstract

Excitonic properties in 2D heterobilayers are closely governed by charge transfer (CT) and excitonic energy transfer (ET) at van der Waals interfaces. Various means have been employed to modulate the interlayer CT and ET, including electrical gating and modifying interlayer spacing, but with limited extent in their controllability. Here, we report a novel method to modulate these transfers in MoS2/WS2 heterobilayer by applying compressive strain under hydrostatic pressure. Raman and photoluminescence measurements, combined with density functional theory calculations show pressure-enhanced interlayer interaction of the heterobilayer. Photoluminescence enhancement factor {\eta} of WS2 in heterobilayer decreases by five times up to ~4 GPa, suggesting a strong ET, whereas it increases by an order of magnitude at higher pressures and reaches almost unity, indicating enhanced CT. Theoretical calculations show that orbital switching in the conduction bands is responsible for the modulation of the transfers. Our findings provide a compelling approach towards effective mechanical control of CT and ET in 2D excitonic devices.