Multiple deformable units enabling superior plasticity and softness in SnS2 van der Waals crystals
Two-dimensional van der Waals (vdW) crystals, stacked via atomically thin layers, exhibit rich functionalities and tunable stacking orders. Their mechanical behaviors are crucial for flexible and miniature electronics. While some vdW crystals show superior plasticity, the mechanical properties of SnS2 bulk crystals remain largely unexplored. Here, we synthesize high-quality SnS2 crystals via the Bridgman method and comprehensively investigate their mechanical properties. SnS2 bulk crystals exhibit remarkable plasticity and softness: bending and compression strains exceed 20% and 45%, respectively, without fracture, while tensile fracture strains reach up to ~12% (range 9%–16%). Scanning/transmission electron microscopy reveals multiple deformation units, including layer segments, interlayer/cross-layer slip, twisting, and twinning-like structures. These units provide multiple pathways to release strain energy, promoting plasticity. Alongside weak interlayer vdW interactions, relatively ionic and weak intralayer Sn–S bonds contribute to the softness. This work fills the knowledge gap on SnS2 mechanical properties, advancing its processing and application in diverse electronic devices. Further studies may focus on balancing plasticity and strength by tuning microstructure to activate but confine deformation units.