Investigation of the mechanical properties and fracture mechanisms of graphene/WSe2 vertical heterostructure: A molecular dynamics study

Assembling layered materials in the form of vertically stacked heterostructures has emerged as a facile way to leverage the properties of each component and fabricate novel highly-tailored architectures with advanced functionalities. In this study, we employ molecular dynamics (MD) simulations to characterize the temperaturedependent tensile mechanical properties of graphene/WSe2 vertical heterostructure along both the armchair and the zigzag directions utilizing a hybrid scheme of various interatomic potentials. It is found that the tensile strength of the WSe2 monolayer can be significantly improved when supported by graphene benefiting from the synergistic effects of their individual strengths. The comparisons of the predicted tensile properties of the heterostructure with that of the mixing rule exhibit excellent conformity. We found that while the bare WSe2 is more resilient to fracture along the armchair direction, the graphene supported WSe2 layer endures larger tensile stress and strain for zigzag loading. This study further reveals fascinating chirality in mechanical properties and failure mechanism of the heterostructure. Fracture initiates from the graphene layer for armchair loading, whereas the WSe2 sheet becomes more prone to fracture under zigzag loading. Crack propagates along the zigzag direction and results in the complete tearing of the specimen for armchair loading, while the crack propagation is confined in a random small region for the zigzag loading. The WSe2 nanosheet experiences major atomic rearrangements and undergoes a phase transformation from trigonal (h-WSe2) to the distorted octahedral phase (t-WSe2) during zigzag loading. Increasing temperature is found to play a crucial role in deteriorating the mechanical properties of the heterostructure. This study offers a comprehensive characterization of the tensile properties of Gr/WSe2 vertical heterostructure and discloses important deformation mechanisms that will enable the efficient utilization of this material.