Nanoparticle stressor-induced single-photon sources in monolayer WS2 emitting into a narrowband visible spectral range

A van der Waals heterostructure containing an atomically thin monolayer (ML) transition-metal dichalcogenide as a single-photon emitting layer is emerging as an intriguing solid-state quantum-photonic platform. Here, we report the utilization of spin-coating of silica nanoparticles for semi-deterministically creating the spectrally isolated, energetically stable, and narrow-linewidth single-photon emitters in ML-WS2. We also demonstrate that long-duration low-temperature annealing of the photonic heterostructure in the vacuum removes the energetically unstable emitters that are present due to fabrication-associated residue and lead to the emission of single-photons in a < 25 nm narrowband visible spectral range centered at similar to 620 nm. This work may pave the way toward realizing a hybrid-quantum-photonic platform containing a van der Waals heterostructure/device and an atomic-vapor system emitting/absorbing in the same visible spectral range.