Localized emission in MoSe$_2$ monolayers on GaN nanopillars

TL;DR

This study investigates the formation of localized quantum emitters in MoSe$_2$ monolayers on GaN nanopillars, revealing that both strain and dielectric environment influence emitter placement, challenging the idea that strain alone is responsible.

Contribution

The paper demonstrates that localized emission in MoSe$_2$ is governed by both strain and dielectric heterogeneity, providing a new framework for deterministic quantum emitter engineering.

Findings

Localized states occur at suspended-supported interfaces, not solely in high-strain regions.

Broad strain range of localized states suggests strain alone does not trigger emission.

Co-engineering strain and dielectric environment enhances quantum emitter positioning.

Abstract

Solid-state quantum emitters (QEs) in two-dimensional semiconductors offer compact, chip-compatible sources for quantum photonics. In transition-metal dichalcogenides (TMDs), nanopillars are widely used to induce localized emission, yet the underlying confinement mechanism and the relative roles of strain versus dielectric environment remain unclear. The general problem addressed here is whether strain alone explains quantum emitter formation and placement in MoSe$_2$, or whether dielectric contrast at suspended-supported interfaces is also required. Here, we combine hyperspectral superlocalization of photoluminescence with co-registered AFM topography and phase to map the positions of localized states (LS) in MoSe$_2$ suspended on GaN pillars and correlate them with bending strain and the local dielectric context. Contrary to the common assumption of purely strain-driven activation, LS frequently occur at suspended--supported interfaces around the pillar apex and span a broad strain range without a clear threshold, while being scarce along high-strain ripples. Our data indicate that deterministic emitter positioning in Mo-based TMDs benefits from co-engineering both strain gradients and nanoscale dielectric heterogeneity, rather than strain alone. More broadly, this combined optical-mechanical characterization approach provides a general framework for mapping structure-property relationships in 2D quantum materials at the single-emitter level.