Local Strain Engineering in Atomically Thin MoS₂

TLDR

Strain tuning is a powerful strategy to modify the electronic properties of semiconductors, and two‑dimensional materials can sustain large strains, enabling local strain engineering for exciton confinement and solar‑energy applications. The study investigates atomically thin MoS₂ layers subjected to up to 2.5 % local strain induced by controlled delamination from a substrate. Local strain was induced by controlled delamination and mapped with simultaneous scanning Raman and photoluminescence imaging, while an atomistic tight‑binding model predicted the strain‑dependent electronic states. The strain reduces the direct bandgap by up to 90 meV, creates a funnel effect that drives excitons hundreds of nanometers toward lower‑bandgap regions, and demonstrates strain‑induced exciton confinement, opening possibilities for photovoltaics, quantum optics, and 2D optoelectronic devices.

Abstract

Tuning the electronic properties of a material by subjecting it to strain constitutes an important strategy to enhance the performance of semiconducting electronic devices. Using local strain, confinement potentials for excitons can be engineered, with exciting possibilities for trapping excitons for quantum optics and for efficient collection of solar energy. Two-dimensional materials are able to withstand large strains before rupture, offering a unique opportunity to introduce large local strains. Here, we study atomically thin MoS2 layers with large local strains of up to 2.5% induced by controlled delamination from a substrate. Using simultaneous scanning Raman and photoluminescence imaging, we spatially resolve a direct bandgap reduction of up to 90 meV induced by local strain. We observe a funnel effect in which excitons drift hundreds of nanometers to lower bandgap regions before recombining, demonstrating exciton confinement by local strain. The observations are supported by an atomistic tight-binding model developed to predict the effect of inhomogeneous strain on the local electronic states in MoS2. The possibility of generating large strain-induced variations in exciton trapping potentials opens the door for a variety of applications in atomically thin materials including photovoltaics, quantum optics and two-dimensional optoelectronic devices.