Uniform Narrow Excitonic Spectrum in Large-Area Suspended WSe2 Monolayers

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.