Power factor enhancement in magnetron sputtered bismuth telluride thermoelectric thin films by stress reduction

The layered structure of bismuth telluride affords greater flexibility for stress manipulation, which has emerged as a promising approach to modulating thermoelectric (TE) properties of thin films. Herein, high-quality Bi₂Te₃ thin films are prepared by the one-step magnetron sputtering, showing considerable potential in large-scale fabrication. By simply tilting the incident angle α, the TE performance of the as-prepared films can be significantly improved. Notably, the presence of massive intragranular defects helps to decrease the macroscale stress stored by the momentum of sputtered atoms. Benefiting from this stress reduction, the carrier concentration and effective mass are simultaneously enhanced, leading to increased electrical conductivity with limited changes to Seebeck coefficient. Consequently, the power factor of Bi₂Te₃ thin films shows about 100% enhancement (14.9 μW·cm⁻¹·K⁻² @523 K) when the Δα/α₀ increases up to 10%. This study demonstrates TE enhancement in thin films via controlled stress reduction, establishing a transferable framework for stress engineering across diverse material platforms.