Synthesis of hetero-site nucleation twisted bilayer MoS2 by local airflow perturbations and interlayer angle characterization

Twisted bilayer transition metal dichalcogenides including MoS 2 have attracted great interest due to their unique Moiré superlattice induced electronic flat bands. High-quality twisted bilayer TMDs with uniform Moiré potentials are essential for the discovery of strong correlation effects, unconventional superconductivity, and quantum anomalous Hall effect. However, the synthesis of large-area high-quality twisted bilayer MoS 2 (tBMoS 2 ) using chemical vapor deposition (CVD) is still absent, which needs to overcome the formation energy barrier for nonstable twist bilayers. Here, we demonstrate a novel CVD approach with local airflow perturbation for growing tBMoS 2 by a heterosite nucleation strategy, which enables the nucleation of the second layer at the different site from the first layer nucleation site with arbitrary twist angles. Furthermore, the accurate determination of interlayer twist angles in tBMoS 2 is crucial for studying structure-physical properties relationship. We quantitatively compare the measurement accuracy between a geometrical method and TEM selected area electron diffractions (SAED), in which the measured angles from TEM-SAED shows much smaller angle errors. Finally, Raman spectra show the interlayer coupling can be tuned by the twist angles. Our study opens an avenue for the controllable growth of tBMoS 2 for both fundamental research and practical applications.