No abstract

The edge elasticity and its effect on flexoelectric response of the Janus MoSSe nanoribbons are systematically explored by means of density functional theory based first-principles calculations. We report edge stresses, edge elastic moduli, and structural deformations of the Janus MoSSe nanoribbons with various widths. It is shown that both armchair and zigzag terminated edges of the MoSSe nanoribbons are essentially subjected to tension, due to the existence of the edge stresses. The magnitude of average zigzag edge stresses is much larger than that of the average armchair ones. Furthermore, our results show that both misfit strain induced by asymmetric chalcogen atomic layers, and the edge stresses cause the spontaneous bending deformation of such Janus nanoribbons. More importantly, flexoelectronic properties of semiconducting armchair MoSSe nanoribbons are carefully evaluated and compared with those of armchair MoS2 and MoSTe nanoribbons. In particular, it is found that the out-of-plane flexoelectronic coefficients strongly depend on their widths. Additionally, the flexoelectric response resulting from spontaneous bending is weaker than that from the opposite one. The implicit mechanisms on deformations and flexoelectronic properties of such Janus nanoribbons have been carefully explored. The results in this work provide useful insights into their potential applications in nanoscale electromechanical systems.

Abstract

This work systematically studied mechanical responses of a novel semiconducting Janus MoSSe monolayer subjected to uniaxial tensile loadings by means of molecular dynamics simulations. It is found that the Janus MoSSe monolayer shows clearly anisotropic responses along armchair and zigzag directions. The phase transition behavior was observed when the Janus MoSSe monolayer is under tension along zigzag direction at temperatures below 100 K, while it does not exist in any other conditions. The Young’s modulus, ultimate strength and ultimate strain decrease as temperature increasing. Particularly, the ductile-to-brittle fracture behavior was observed when uniaxial tension is applied along zigzag direction depending on temperatures. The underline fracture mechanism was analyzed. Moreover, mechanical properties of Janus MoSSe monolayer with various grain boundaries were also carefully explored. It is found that the ultimate strength and ultimate strain depend more sensitively for narrow grains than those wider ones. The crack is initialized near the grain boundaries and propagated along direction almost perpendicular to the grain boundaries. The findings of this work may shed some lights on design and optimization of nanoscale electronic devices based on the Janus MoSSe monolayers.