Strong Zero-Phonon Transition from Point Defect-Stacking Fault Complexes in Silicon Carbide Nanowires.

Crystallographic defects such as vacancies and stacking faults engineer electronic band structure at the atomic level and create zero- and two-dimensional quantum structures in crystals. The combination of these point and planar defects can generate a new type of defect complex system. Here, we investigate silicon carbide nanowires that host point defects near stacking faults. These point-planar defect complexes in the nanowire exhibit outstanding optical properties of high-brightness single photons (>360 kcounts/s), a fast recombination time (<1 ns), and a high Debye-Waller factor (>50%). These distinct optical properties of coupled point-planar defects lead to an unusually strong zero-phonon transition, essential for achieving highly efficient quantum interactions between multiple qubits. Our findings can be extended to other defects in various materials and therefore offer a new perspective for engineering defect qubits.

Position and Frequency Control of Strain-Induced Quantum Emitters in WSe2 Monolayers.

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 WSe2 monolayer. The integrated WSe2 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%.

High-Crystalline Monolayer Transition Metal Dichalcogenides Films for Wafer-Scale Electronics.

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.