Differences in the Mechanical Properties of Monolayer and Multilayer WSe2/MoSe2

TL;DR

This study uses molecular dynamics simulations to compare the mechanical properties of monolayer and multilayer WSe2 and MoSe2, revealing layer-dependent friction, fracture behaviors, and substrate interactions.

Contribution

It provides detailed atomistic insights into how layer number affects the mechanical and fracture properties of WSe2 and MoSe2, a topic previously underexplored.

Findings

Monolayer WSe2/MoSe2 have higher friction coefficients than multilayers.

MoSe2 structures are easier to peel off and fracture.

Fracture patterns depend on chirality and bond orientation.

Abstract

Transition metal dichalcogenides are 2D structures with remarkable electronic, chemical, optical and mechanical properties. Monolayer and crystal properties of these structures have been extensively investigated, but a detailed understanding of the properties of their few-layer structures are still missing. In this work we investigated the mechanical differences between monolayer and multilayer WSe2 and MoSe2, through fully atomistic molecular dynamics simulations (MD). It was observed that single layer WSe2/MoSe2 deposited on silicon substrates have larger friction coefficients than 2, 3 and 4 layered structures. For all considered cases it is always easier to peel off and/or to fracture MoSe2 structures. These results suggest that the interactions between first layer and substrate are stronger than interlayer interactions themselves. Similar findings have been reported for other nanomaterials and it has been speculated whether this is a universal-like behavior for 2D layered materials. We have also analyzed fracture patterns. Our results show that fracture is chirality dependent with crack propagation preferentially perpendicular to W(Mo)-Se bonds and faster for zig-zag-like defects.