Effect of Triangular Pre-Cracks on the Mechanical Behavior of 2D MoTe$_2$: A Molecular Dynamics Study

Abstract

Among two-dimensional (2D) materials, transition metal dichalcogenides (TMDs) stand out for their remarkable electronic, optical, and chemical properties. In addition to being variable bandgap semiconductor materials, the atomic thinness provides flexibility to TMDs. Therefore, understanding the physical properties of TMDs for applications in flexible and wearable devices is crucial. Despite the growing enthusiasm surrounding two-dimensional transition metal dichalcogenides (TMDs), our understanding of the mechanical characteristics of molybdenum ditelluride (MoTe$_2$) remains limited. The mechanical properties of MoTe$_2$ deteriorate in the presence of pre-existing cracks or vacancy defects, which are very common in grown TMDs. In this study, the fracture properties and crack propagation of monolayer molybdenum ditelluride (MoTe$_2$) sheets containing pre-existing triangular cracks with various vertex angles are investigated by performing molecular dynamics (MD) simulations of uniaxial and biaxial tensile loading. Due to pre-crack length, angle, and perimeter variations, monolayer MoTe$_2$ with pre-existing cracks underwent considerable changes in Young's modulus, tensile strength, fracture toughness, and fracture strain values. We have found that the pre-cracked MoTe$_2$ is more brittle than its pristine counterpart. Regulated alteration of pre-crack angle under constant simulation conditions improved the uniaxial mechanical properties. Similarly, regulated alteration of the perimeter of the pre-crack resulted in improved biaxial mechanical properties. This study contributes to the foundational knowledge for advanced design strategies involving strain engineering in MoTe$_2$ and other similar transition metal dichalcogenides.