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 (101¯0) plane, whereas in thick samples, crack paths comply with the plane stress distribution rule and reside on the (112¯0) 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.