High-Performance Bi0.4Sb1.6Te3 Films via Thickness-Induced Texturing and Twin Boundaries

The development of high-performance bismuth telluride thin films is essential for technological innovation in miniature thermoelectric devices. However, decoupling electrical and thermal transport in polycrystalline films remains challenging. Here, we report a synergistic strategy that combines thickness-induced texturing with defect engineering to enhance the thermoelectric properties of p-type Bi0.4Sb1.6Te3 films. Employing Te-compensated magnetron sputtering, the (00l) orientation factor increased from 0.17 to 0.39 as thickness increased from 500 to 800 nm. This (00l) texture provides low-scattering pathways for hole transport, while Te compensation effectively regulates carrier concentration, thereby contributing to an enhanced Seebeck coefficient. Importantly, a dense network of coherent 60° nanotwinned boundaries forms within the film, serving dual roles: acting as efficient phonon-scattering centers that significantly suppress lattice thermal conductivity while maintaining favorable carrier transport owing to their interfacial characteristics. Ultimately, the optimized 800 nm film exhibits high thermoelectric performance: a power factor as high as approximately 40 μW·cm-1·K-2 at room temperature and an in-plane thermal conductivity as low as approximately 0.83 W·m-1·K-1, achieving a high thermoelectric figure of merit (zT) of 1.43. This work provides a simple and effective practical strategy for mitigating the electrical and thermal transport trade-off in thermoelectric films.