Stacking fault-induced strengthening mechanism in thermoelectric semiconductor Bi₂Te₃

The weak Te-Te van der Waals (vdW) interaction is the origin of the poor mechanical strength of Bi₂Te₃, leading to a low micro-machining yield of thermoelectric micro-devices. This largely restricts its commercial applications in such fields as 5G and the Internet of Things. Here, we apply large-scale molecular dynamics simulations to discover that the formation of new stacking faults (SFs) can be introduced from slippage of Te-Te vdW layers during shearing of Bi₂Te₃. With a high density (>70%) of SFs, all vdW layers eventually evolve into a full SF structure with a reduced interlayer Te-Te length that remarkably strengthens the vdW Te-Te interaction, hence increasing the ultimate shear strength to be three times stronger. This different structural evolution depends on the competitive relationship between SF formation energy and cleavage energy. This work demonstrates an SF strategy to develop robust layered materials by improving the vdW interactions.