Uniform Narrow Excitonic Spectrum in Large-Area Suspended WSe2 Monolayers

TL;DR

This study demonstrates that suspended WSe2 monolayers exhibit highly uniform excitonic spectra with narrow linewidths, achieved through gold-assisted exfoliation, enabling intrinsic optical properties and electrical tunability.

Contribution

The paper introduces a fabrication method for high-quality suspended WSe2 monolayers with uniform excitonic spectra, reducing substrate effects and contamination.

Findings

Uniform excitonic photoluminescence with linewidths as low as 4.5 meV.

Suspended membranes up to 80 μm exhibit consistent optical responses.

Gate-dependent measurements reveal multiple excitonic species.

Abstract

Uniformity in the excitonic spectrum is a key requirement for accessing intrinsic excitonic physics in two-dimensional semiconductors; however, in transition-metal dichalcogenide (TMD) monolayers supported on substrates, exciton energies and linewidths can vary spatially due to inhomogeneities from contact with other materials or fabrication residues. Suspended TMD monolayers provide a route to minimizing substrate-induced disorder, although conventional transfer processes can introduce contamination. Here we demonstrate the spatially uniform excitonic spectrum from optically high-quality WSe2 suspended monolayers fabricated by gold-assisted exfoliation directly onto an Au contact electrode of a gate-tunable device. The resulting membranes span narrow suspended regions up to ~80 um and show spatially uniform photoluminescence at cryogenic temperatures with neutral-exciton linewidths as low as ~4.5 meV. Spectral reproducibility supports an intrinsic optical response, while gate-dependent measurements resolve multiple excitonic species. This approach provides a route to electrically tunable potential landscapes in suspended TMD monolayers with a highly uniform excitonic response.