Order-Tuned Deformability of Bismuth Telluride Semiconductors: An Energy-Dissipation Strategy for Large Fracture Strain.

Abstract

In addition to thermoelectric (TE) performance tuning through defect or strain engineering, progress in mechanical research is of increasing importance to wearable applications of bismuth telluride (Bi2Te3) TE semiconductors, which are limited by poor deformability. For improving dislocation-controlled deformability, we clarify an order-tuned energy-dissipation strategy that facilitates large deformation through multilayer alternating slippage and stacking fault destabilization. Given that energy dissipation and dislocation motions are governed by van der Waals sacrificial bond (SB) behavior, molecular dynamics simulation is implemented to reveal the relation between the shear deformability and lattice order changes in Bi2Te3 crystals. Using the disorder parameter (D) that is defined according to the configurational energy distribution, the results of strain rates and initial crack effects show how the proper design of the initial structure and external conditions can suppress strain localization that would cause structural failure from the lack of energy dissipation, resulting in large homogeneous deformation of Bi2Te3 nanocrystals. This study uncovers the essence of the tuning mechanism in which highly deformable Bi2Te3 crystals should become disordered as slowly as possible until fracture. This highlights the role of the substructure evolution of SB-defect synergy that facilitates energy dissipation and performance stability during slipping. The disorder parameter D provides a bridge between micro/local mechanics and fracture strain, hinting at the possible mechanical improvement of Bi2Te3 semiconductors for designing flexible TE devices through order tuning and energy dissipation.