Homo-Site Nucleation Growth of Twisted Bilayer MoS with Commensurate Angles.

Moiré superlattices, composed of two layers of transition metal dichalcogenides with a relative twist angle, provide a novel platform for exploring the correlated electronic phases and excitonic physics. Here, a gas-flow perturbation chemical vapor deposition (CVD) approach is demonstrated to directly grow MoS bilayer with versatile twist angles. It is found that the formation of twisted bilayer MoS homostructures sensitively depends on the gas-flow perturbation modes, correspondingly featuring the nucleation sites of the second layer at the same (homo-site) as or at the different (hetero-site) from that of the first layer. The commensurate twist angle of ≈22° in homo-site nucleation strategy accounts for ≈16% among the broad range of twist angles due to its low formation energy, which is in consistence with the theoretical calculation. More importantly, moiré interlayer excitons with the enhanced photoluminescence (PL) intensity and the prolonged lifetime are evidenced in the twisted bilayer MoS with a commensurate angle of 22°, which is owing to the reason that the strong moiré potential facilitates the interlayer excitons to be trapped in the moiré superlattices. The work provides a feasible route to controllably built twisted MoS homostructures with strong moiré potential to investigate the correlated physics in twistronics systems.