Chemical
vapor deposition (CVD) using liquid-phase precursors has
emerged as a viable technique for synthesizing uniform large-area
transition metal dichalcogenide (TMD) thin films. However, the liquid-phase
precursor-assisted growth process typically suffers from small-sized
grains and unreacted transition metal precursor remainders, resulting
in lower-quality TMDs. Moreover, synthesizing large-area TMD films
with a monolayer thickness is also quite challenging. Herein, we successfully
synthesized high-quality large-area monolayer molybdenum diselenide
(MoSe2) with good uniformity via promoter-assisted liquid-phase
CVD process using the transition metal-containing precursor homogeneously
modified with an alkali metal halide. The formation of a reactive
transition metal oxyhalide and reduction of the energy barrier of
chalcogenization by the alkali metal promoted the growth rate of the
TMDs along the in-plane direction, enabling the full coverage of the
monolayer MoSe2 film with negligible few-layer regions.
Note that the fully selenized monolayer MoSe2 with high
crystallinity exhibited superior electrical transport characteristics
compared with those reported in previous works using liquid-phase
precursors. We further synthesized various other monolayer TMD films,
including molybdenum disulfide, tungsten disulfide, and tungsten diselenide,
to demonstrate the broad applicability of the proposed approach.
Future scalable and integrated quantum photonic systems require deterministic generation and control of multiple quantum emitters. Although various approaches for spatial and spectral control of the quantum emitters have been developed, on-chip control of both position and frequency is still a long-standing goal in solid-state quantum emitters. Here, we demonstrate simultaneous control of position and frequency of the quantum emitters from transition metal dichalcogenide monolayers. Atomically thin two-dimensional materials are inherently sensitive to external strain and offer a new opportunity of creating and controlling the quantum emitters by engineering strain. We fabricate an electrostatically actuated microcantilever with nanopyramid patterns, providing a local strain engineering platform for the WSe 2 monolayer. The integrated WSe 2 generates high-purity single photon emission at patterned positions with a tuning range up to 3.5 meV. Together with the position and frequency control, we investigate the strain response on the fine-structure splitting and confirm 11% reduction in the fine splitting at the estimated tensile strain of 0.07%.
Incorporating solid-state quantum emitters into optical fiber networks enables the long-distance transmission of quantum information and the remote connection of distributed quantum nodes. However, interfacing quantum emitters with fiber optics encounters several challenges, including low coupling efficiency and delicate configuration. In this study, a highly efficient fiber-interfacing photonic device that directly launches single photons from quantum dots into a standard FC/PC-connectorized single-mode fiber is demonstrated. Optimally designed photonic structures based on hole gratings produce an ultra-narrow directional beam that matches the small numerical aperture of a single-mode fiber. A pick-and-place technique precisely integrates a single miniaturized device into the core of the fiber. This approach realizes a plug-and-play single-photon device that does not require optical alignment and thus guarantees long-term stability. The results represent a major step toward practical and reliable transmission of quantum light across a fiber network.
By integrating WSe2 monolayers with a nanopatterned Si micro-cantilever, we create the quantum emitters at deterministic sites and control their frequency with voltages. Also, reduction of the fine-structure splitting is observed by engineering the strain.
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