Reversible local strain engineering of $\mathrm{WS}_2$ using a micro-mechanical spring

TL;DR

This paper introduces a reversible, programmable method for local strain engineering in suspended $ ext{WS}_2$ using a micro-mechanical spring, enabling dynamic control and systematic study of strain effects in 2D materials.

Contribution

The study presents a novel, substrate-free platform for reversible and programmable local strain control in 2D materials using a micro-mechanical spring with nanoscale probes.

Findings

Reversible redshift of exciton peak under strain

Programmable in-plane strain distribution via probe geometry

Demonstration of various strain configurations (point-like, uniaxial, biaxial, triaxial)

Abstract

Local strain engineering is a promising technique to tune the properties of two-dimensional materials at the nanoscale. However, many existing methods are static and limit the systematic exploration of strain-dependent material behavior. Here, we demonstrate dynamic and reversible control of local strain distributions in suspended trilayer tungsten disulfide ($\mathrm{WS}_2$) via nanoindentation using a micro-mechanical spring patterned with nanoscale probes. Micro-photoluminescence measurements reveal that indentation using a ring-shaped probe induces a nearly uniform biaxial strain distribution accompanied by a reversible redshift of the neutral exciton peak, consistent with simulated strain magnitudes. We further show that the in-plane strain distribution is spatially programmable by engineering the probe geometry and present designs for inducing point-like, uniaxial, biaxial, and triaxial strain distributions. The presented platform enables substrate-free, repeatable local strain engineering in suspended 2D materials and provides a versatile tool for streamlining the investigation of strain-dependent phenomena.