Reduced Fracture Strength of 2D Materials Induced by Interlayer Friction

Abstract

The potential applications of 2D layered materials (2DLMs) as the functional membranes in flexible electronics and nano‐electromechanical systems emphasize the role of the mechanical properties of these materials. Interlayer interactions play critical roles in affecting the mechanical properties of 2DLMs, and nevertheless the understanding of their relationship remains incomplete. In the present work, it is reported that the fracture strength of few‐layer (FL) WS2 can be weakened by the interlayer friction among individual layers with the assistance of finite element simulations and density functional theory (DFT) calculations. The reduced fracture strength can be also observed in FL WSe2 but with a lesser extent, which is attributed to the difference in the interlayer sliding energies of WS2 and WSe2 as confirmed by DFT calculations. Moreover, the tip‐membrane friction can give rise to the underestimation of the Young's modulus except for the membrane nonlinearity. These results give deep insights into the influence of interfacial interactions on the mechanical properties of 2DLMs, and suggest that importance should be also attached to the interlayer interactions during the design of nanodevices with 2DLMs as the functional materials.

Layer-dependent fracture strength of few-layer WS2 induced by interlayer sliding: a molecular dynamics study

“…Moreover, the fracture strains were ∼0.20 for the armchair direction and ∼0.23 for the zigzag direction, respectively. Elastic and fracture properties obtained by the modified SW parameters were consistent with our previous experimental results [32]. The small peak marked by a green circle in figure 1(b) may be attributed to the reunion behavior of the atoms after the break occurred (details shown in figure S1 in the supporting information).…”

“…The time step was 0.001 ps, and the code for tensile behavior was fix deform. In our previous work, the in-plane mechanical properties of monolayer WS 2 have been experimentally measured [32], providing a reference for modifying the parameters of the SW potential via in-plane tensile simulations. As shown in figure 1(a), the dimension of the monolayer WS 2 simulation cell was ∼105 × 102 Å 2 (consisting of 3648 atoms), and periodic boundary conditions were applied in all directions.…”

Recent advances in the mechanics of 2D materials

“…Such degradation becomes more significant when the layers are in an incommensurate stacking configuration, because of a lower interlayer shear strength that enables interlayer slippage. The reduced fracture strength can also be visible in few-layer WS 2 but to a lesser extent [219]. This finding can be explained by the difference in the interlayer sliding energies of WS 2 and graphene, as confirmed by DFT calculations.…”

Comparative analysis of frictional behavior and mechanism of molybdenum ditelluride with different structures

“…The bilayer MoTe 2 and CH 4 molecules were first optimized separately, and then combined for structural optimization. For calculating the sliding energy, the atoms of the MoTe 2 were fixed for VASP selective dynamics, while the CH 4 molecule was displaced at different positions, restricting the degree of freedom of the in-plane positions [33][34][35].…”