Locally defined quantum emission from epitaxial few-layer tungsten diselenide

Recently, single photons have been observed emanating from point defects in two-dimensional (2D) materials including WSe₂, WS₂, hexagonal-BN, and GaSe, with their energy residing in the direct electronic bandgap. Here, we report single photon emission from a nominal weakly emitting indirect bandgap 2D material through deterministic strain induced localization. A method is demonstrated to create highly spatially localized and spectrally well-separated defect emission sites in the 750-800 nm regime in a continuous epitaxial film of few-layer WSe₂ synthesized by a multistep diffusion-mediated gas source chemical vapor deposition technique. To separate the effects of mechanical strain from the substrate or dielectric-environment induced changes in the electronic structure, we created arrays of large isotropically etched ultrasharp silicon dioxide tips with spatial dimensions on the order of 10 μm. We use bending based on the small radius of these tips - on the order of 4 nm - to impart electronic localization effects through morphology alone, as the WSe₂ film experiences a uniform SiO₂ dielectric environment in the device geometry chosen for this investigation. When the continuous WSe₂ film was transferred onto an array of SiO₂ tips, an ∼87% yield of localized emission sites on the tips was observed. The outcomes of this report provide fundamental guidelines for the integration of beyond-lab-scale quantum materials into photonic device architectures for all-optical quantum information applications.