So far, the quantum emitters (QEs) had been assigned to both defects and strain gradients, mostly unwanted and unpredictable.
In a recent paper published in Nature Communications under the title "Large-scale quantum-emitter arrays in atomically thin semiconductors", researchers from the University of Cambridge (UK) together with scientists from Harvard University (US) demonstrated how they were able to localize the sources of single photons by tuning the topography of such 2D materials.
The paper discloses how by placing the active material (a monolayer of exfoliated WSe2 or WS2) on top of nanopillars regularly spaced apart, the researchers obtained an array of tent-shaped peaks distributed across the monolayer, forming localized physical disturbances from which single photons were emitted.
SiO2 nanopillars, 150nm in diameter and ranging from 60 to 190nm in height, were first created onto a silica substrate to form an array with a 4µm pitch (using a high-resolution direct-write lithographic process).
By placing tungsten diselenide and tungsten disulphide monolayers on top of such arrays (using an all-dry viscoelastic deposition process), the researchers created deterministic arrays of hundreds of QEs emitting across a range of wavelengths in the visible spectrum (610–680 nm and 740–820nm respectively).
In their paper, the researchers explain that the localized deformations created by the nanopillars result in the quantum confinement of excitons.