For two-dimensional (2D) layered semiconductors, control over atomic defects and understanding of their electronic and optical functionality represent major challenges towards developing a mature semiconductor technology using such materials. Here, we correlate generation, optical spectroscopy, atomic resolution imaging, and ab initio theory of chalcogen vacancies in monolayer MoS2. Chalcogen vacancies are selectively generated by in-vacuo annealing, but also focused ion beam exposure. The defect generation rate, atomic imaging and the optical signatures support this claim. We discriminate the narrow linewidth photoluminescence signatures of vacancies, resulting predominantly from localized defect orbitals, from broad luminescence features in the same spectral range, resulting from adsorbates. Vacancies can be patterned with a precision below 10 nm by ion beams, show single photon emission, and open the possibility for advanced defect engineering of 2D semiconductors at the ultimate scale.
We demonstrate the on-demand creation
and positioning of photon
emitters in atomically thin MoS2 with very narrow ensemble
broadening and negligible background luminescence. Focused helium-ion
beam irradiation creates 100s to 1000s of such mono-typical emitters
at specific positions in the MoS2 monolayers. Individually
measured photon emitters show antibunching behavior with a g
2(0) ∼ 0.23 and 0.27. From a statistical
analysis, we extract the creation yield of the He-ion induced photon
emitters in MoS2 as a function of the exposed area, as
well as the total yield of single emitters as a function of the number
of He ions when single spots are irradiated by He ions. We reach probabilities
as high as 18% for the generation of individual and spectrally clean
photon emitters per irradiated single site. Our results firmly establish
2D materials as a platform for photon emitters with unprecedented
control of position as well as photophysical properties owing to the
all-interfacial nature.
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