Reduced Fracture Anisotropy yet Enhanced Deformability of Multilayer MoS₂ Straps

The mechanical properties of two-dimensional transition metal dichalcogenides (2D TMDs), molybdenum disulfide (MoS₂) in particular, are crucial for their reliable applications in advanced flexible electronics and phototransistors. This study systematically investigated the influence of geometrical factors on MoS₂'s mechanical property and fracture behavior by performing in situ tensile tests on submicroscale strap specimens with different thicknesses ranging from 7 to 95 nm inside SEM and TEM. Results demonstrated a strong correlation between the apparent fracture strength and Young's modulus of MoS₂ and the specimen thickness, where thinner samples exhibited a significantly elevated fracture strength and Young's modulus. Moreover, a distinct mechanism transition in the fracture modes was revealed: in thin samples, cracks tend to propagate along the low surface energy $\left(10\overline{1}0\right)$ plane, whereas in thick samples, crack paths comply with the plane stress distribution rule and reside on the $\left(11\overline{2}0\right)$ principal stress plane, exhibiting reduced fracture anisotropy. Additionally, an interlayer sliding behavior was discovered as a mechanical energy dissipating mechanism to enhance the deformability of MoS₂ and retard rupture. These discoveries provide fundamental insights into the mechanical stability of MoS₂, boosting the development of high-performance 2D materials for flexible electronics and nanomechanical systems.