Micro-mechanism of the size effect on the deformation homogeneity of Sb₂Te₃ semiconductors

Sb₂Te₃ based semiconductors are state-of-the-art commercial thermoelectric (TE) materials at room temperature. To improve the performance stability of Sb₂Te₃ TE semiconductors and relevant applications in wearable devices, it is necessary to enhance their deformability. Although Sb₂Te₃ easily fractures along the weakly bonded Van der Waals (VdW) layers, the dislocation slip process on these layers can be facilitated by modulating the weak but reversible VdW bonds, implying the potential for improvement of the plastic deformation capacity. Here, taking structural homogeneity as the characteristic evaluation criterion of the whole deformation process, the size effect of Sb₂Te₃ nanocrystals on the evolution of lattice defects and plastic deformation capacity is investigated by shear deformation in molecular dynamics. The results show that the influence of lattice distortion at the boundaries is weakened with the increasing structural size, which promotes the ordered breaking-reforming process of VdW bonds and alternating dislocation slips on VdW-coupled atomic layers. It reveals a close relationship between VdW bonds and defects during structural evolution, and therefore a microscale manner of energy dissipation and deformation coordination that is conducive to strain delocalization and fracture strain enhancement. This simulation work provides new insights into the plastic deformation mechanism of inorganic semiconductors given the effect of surface and crystal size, which will improve the defect engineering strategy for designing advanced TE semiconductors.