Thermoelectric Properties and Shubnikov-de Haas Oscillations in Tin-Doped Bismuth Wires

Using a set of glass-insulated Bi–0.02at.%Sn wires with diameters varying in a range of 0.2–1 µm prepared by liquid-phase casting via the Ulitovsky method, a complex of measurements of the temperature depen-dences of resistivity ρ(T), thermoelectric power α(T), and magnetic field dependences R(H) in a range of 4.2–300 K and Shubnikov-de Haas (SdH) oscillations in longitudinal and transverse magnetic fields up to 14 T in a temperature range of 2.1–20 K has been conducted. According to the SdH oscillation measurements, the minimum and maximum cyclotron masses, the Dingle temperature, and the position of the Fermi level ε_F in the Bi–0.02at.%Sn wires have been calculated. It has been shown that, at low temperatures, the conduction occurs only through T-holes, i.e., ε_F is located in the region of the band gap ΔE_g; it has been found that the anisotropy of the Fermi surface of the T-holes does not change after doping. The observed anomalies in the temperature dependences ρ(T), α(T), and at longitudinal magnetic field dependences R(H), which depends on the wire diameter d, have been interpreted in terms of the occurrence of galvanomagnetic size effects. From the experimental data, power factor P.f. = α²σ for the Bi–0.02at.%Sn wires with different diameters in a range of 4.2–300 K has been calculated as well as the maximum P.f. value in different temperature ranges. It has been found that the maximum P.f. value is achieved in a temperature range of 75–100 K when the thermoelectric power has a positive value, which is an important factor for thermoelectric applications at low temperatures.