Mechanical Properties of Monolayer MoS2 with Randomly Distributed Defects

Abstract

The variation of elastic constants stiffness coefficients with respect to different percentage ratios of defects in monolayer molybdenum disulfide (MLMoS₂) is reported for a particular set of atomistic nanostructural characteristics. The common method suggested is to use conventional defects such as single vacancy or di vacancy, and the recent studies use stone-walled multiple defects for highlighting the differences in the mechanical and electronic properties of 2D materials. Modeling the size influence of monolayer MoS₂ by generating defects which are randomly distributed for a different percentage from 0% to 25% is considered in the paper. In this work, the geometry of the monolayer MoS₂ defects modeled as randomized over the domain are taken into account. For simulation, the molecular static method is adopted and study the effect of elastic stiffness parameters of the 2D MoS₂ material. Our findings reveals that the expansion of defects concentration leads to a decrease in the elastic properties, the sheer decrease in the elastic properties is found at 25%. We also study the diffusion of Molybdenum (Mo) in Sulphur (S) layers of atoms within MoS₂ with Mo antisite defects. The elastic constants dwindle in the case of antisite defects too, but when compared to pure defects, the reduction was to a smaller extent in monolayer MoS₂. Nevertheless, the Mo diffusion in sulfur gets to be more and more isotropic with the increase in the defect concentrations and elastic stiffness decreases with antisite defects concentration up to 25%. The distribution of antisite defects plays a vital role in modulating Mo diffusion in sulfur. These results will be helpful and give insights in the design of 2D materials.

Keywords: defects; mechanical properties; molecular statics/dynamics; mono-layer MoS2; random distributed defects.

Figure 1

(a) Unit cell of hexagonal MoS₂ (b) 15a × 15a × 1a MoS₂ bulk structure (S = Blue or light; Mo = Purple).

Figure 2

The atomistic model of monolayer MoS₂ without defects, blue balls represents Sulphur atoms top and bottom layers and red balls represent Molybdenum. The elastic constants for this pristine MoS₂ are C₁₁ = C₂₂ = 149.42 N/m, C₁₂ = 52.29 N/m. (a) Side and isometric view (b) top view.

Figure 3

The atomistic model of monolayer MoS₂ with different percentge of defects.

Figure 4

The elastic constants of MoS₂ as a function of the defect fraction: (a) C₁₁, (b) C₂₂, (c) C₁₂.

Figure 4

The elastic constants of MoS₂ as a function of the defect fraction: (a) C₁₁, (b) C₂₂, (c) C₁₂.

Figure 5

The atomistic model of monolayer MoS₂ with different percentage of antisite defects.

Figure 6

The elastic constants of MoS₂ as a function antisite defect fraction: (a) C₁₁, (b) C₂₂, (c) C₁₂.