Enhanced thermoelectric power factor in in-situ high-vacuum annealed Bi_1-xSb_x films with compact morphology by magnetron sputtering

Thermoelectric performances of thin films are affected by both the morphology and composition of the films. On one hand, the compact morphology of films could increase electrical conductivity via boosting carrier mobility. On the other hand, for semimetal or semiconductor materials, alloying is an effective means to adjust the carrier concentration and band structure and further modulate thermoelectric performances. In this work, with an in-situ high-vacuum annealing technique, we prepared compact Bi_1-xSb_x thin films via magnetron sputtering and further modulated their power factor by varying Sb content. Thermoelectric transport measurements revealed an enhanced room-temperature power factor up to 23.48 μW/(cmK²) in compact Bi_0.95Sb_0.05 film with high carrier mobility. Our simulation results based on a tight-binding model, in conjunction with the experimentally observed mobility peak, suggest that the observation of enhanced thermoelectric power factor is possibly related to the composition-induced band structure modulation.