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 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mo>(</mml:mo><mml:mn>10</mml:mn><mml:mover><mml:mn>1</mml:mn><mml:mo>¯</mml:mo></mml:mover><mml:mn>0</mml:mn><mml:mo>)</mml:mo></mml:math> plane, whereas in thick samples, crack paths comply with the plane stress distribution rule and reside on the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mo>(</mml:mo><mml:mn>11</mml:mn><mml:mover><mml:mn>2</mml:mn><mml:mo>¯</mml:mo></mml:mover><mml:mn>0</mml:mn><mml:mo>)</mml:mo></mml:math> 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.