Fabrication and electrical properties of Bi2-xSbxTe3 ternary nanopillars array films

Highly oriented Bi 2-x Sb x Te 3 (x = 0, 0.7, 1.1, 1.5, 2) ternary nanocrystalline films were fabricated using vacuum thermal evaporation method. Microstructures and morphologies indicate that Bi 2-x Sb x Te 3 films have pure rhombohedral phase with well-ordered nanopillars array. Bi, Sb and Te atoms uniformly distributed throughtout films with no precipitation. Electrical conductivity of Bi 2-x Sb x Te 3 films transforms from n-type to p-type when x > 1.1. Metal-insulator transition was observed due to the incorporation of Sb in Bi 2 Te 3 . Bi 2-x Sb x Te 3 film with x = 1.5 exhibits optimized electrical properties with maximum electrical conductivity σ of 2.95 × 10 5 S m −1 at T = 300 K, which is approximately ten times higher than that of the undoped Bi 2 Te 3 film, and three times higher than previous report for Bi 0.5 Sb 1.5 Te 3 films and bulk materials. The maximum power factor PF of Bi 0.5 Sb 1.5 Te 3 nanopillars array film is about 3.83 μW cm −1 K −2 at T = 475 K. Highly oriented (Bi,Sb) 2 Te 3 nanocrystalline films with tuned electronic transport properties have potentials in thermoelectric devices.