Chirality dependent electromechanical properties of single-layer MoS2 under out-of-plane deformation: a DFT study

Abstract

2D transition metal dichalcogenides (TMDs) demonstrate significant promise in logic circuits and optoelectronic devices because of their unique structures and excellent semiconductor properties. However, they inevitably undergo out-of-plane deformation during practical applications due to their ultra-thin structures. Recent experiments have shown that out-of-plane deformation significantly affects the electronic structures of 2D TMDs. However, the underlying physical mechanism is largely unknown. Therefore, it is critical to have a deeper understanding of out-of-plane deformation in 2D TMDs to optimize their applications in different fields. Currently, one of the most pressing matters that requires clarification is the chirality dependence of out-of-plane deformation in tuning the electromechanical properties of 2D TMDs. In this work, using single-layer MoS₂ as a probe, we systematically investigate the effects of out-of-plane deformation along different chirality directions on the bond length, bending stiffness, electric polarization, and band structure of 2D TMDs by employing first-principles calculations based on density functional theory. Our results indicate that the bond length, bending energy, polarization strength, and band gap size of single-layer MoS₂ are isotropic under out-of-plane deformation, while the band gap type is closely related to the direction of deformation. Our study will provide an essential theoretical basis for further revealing the structure–performance relationship of 2D TMDs.