Thermoelectric Properties and Shubnikov–de Haas Oscillations in Bi Wires Doped with Sn

Abstract

Using a set of glass-insulated Bi–0.02 at %Sn wires with diameters varying in a range of 0.2–1 μm prepared by liquid-phase casting by the Ulitovsky method, a complex of measurements of the temperature dependences of resistivity ρ(T), thermoelectric power α(T), and magnetic field dependences R(H) in range 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 eF in the Bi–0.02 at %Sn wires have been calculated. It has been shown that, at low temperatures, the conduction occurs only through T-holes, i.e., eF is located in the region of the band gap ΔEg; 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 on longitudinal magnetic field dependences R(H), which depend on 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–0.02 at %Sn wires with different diameters in a range of 4.2–300 K has been calculated; the maximum P.f. value in different temperature ranges has been calculated. 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.