Inversion Symmetry and Exotic Interlayer Exciton Behavior in Twisted Trilayer MoS 2 Produced by Vapor Deposition.

Two-dimensional materials (2DMs) that are stacked vertically with a certain twist angle provide new degrees of freedom for designing novel physical properties. Twist-related properties of homogeneous bilayer and heterogeneous bilayer 2DMs, such as excitons and phonons, have been described in many pioneering works. However, twist-related properties of homogeneous trilayer 2DMs have been rarely reported. In this work, trilayer MoS 2 with the twisted angle of 12° by optimized vapor deposition rather than the conventional mechanical stacking method was successfully fabricated. The inversion symmetry of trilayer MoS 2 is changed by twist. Phonons and excitons produced by twist have an enormous influence on the interlayer interaction of trilayer MoS 2 , making trilayer MoS 2 appear to have exotic optical properties. Compared with monolayer MoS 2 , the phonon vibration and photoluminescence intensity of trilayer MoS 2 with one-interlayer-twisted are significantly improved, and the second harmonic generation response in the non-twist region of trilayer MoS 2 is ∼3 times that of monolayer MoS 2 . In addition, interlayer coupling, inversion symmetry, and exciton behavior of the twist region show regional differences. This work provides a new way for designing twist and exploring the influence of twist on the structures of 2DMs with few layers.