ACS Nano Article ASAP, https://doi.org/10.1021/acsnano.8b08730 (2019)

Good single-photon emitters (SPEs) should produce single, indistinguishable photons on demand and at a high rate, from well-defined positions in a device. Two-dimensional materials are attractive hosts for SPEs because they conveniently integrate with photonic circuits and enable efficient coupling into photonic waveguides or cavities. Furthermore, in transition metal dichalcogenides, local strain can induce SPEs. But precise positioning is a challenge.

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American Chemical Society

Rosenberger et al. now use an atomic force microscope (AFM) to induce SPEs in a WSe2 monolayer with submicrometre precision. They place the WSe2 on a polymer layer on a SiO2/Si substrate and indent the tip of the AFM into this sample at predefined positions. The plastic deformation of the polymer stabilizes the indentation in the WSe2 after the tip has been retracted because the WSe2 monolayer adheres to the polymer layer below. Subsequent AFM measurements confirm the creation of notches, whose shape and size depend on the applied force and the tip shape.

The researchers then perform photoluminescence experiments. They detect increased photoluminescence intensity, sharp emission lines and antibunching behaviour up to a temperature of 60 K. These experiments unveil the SPE character of the indents; the exact nature of the emitter, however, remains obscure at this stage.