The impact of dimensions, magnetic field, elastic deformation on the thermoelectric figure of merit of the topological insulator wires based on semiconductor Bi1-xSbx wires

Abstract

This paper presents the experimental results of a study of thermoelectric properties of the topological insulator (TI) wires based on semiconductor Bi1-xSbx wires. Glass-coated semiconductor Bi-17 at % Sb wires prepared by the Ulitovsky liquid phase casting method were single crystals strictly of cylindrical shape with diameters ranging from 100 nm to 1000 nm and crystallographic orientation (1011) along the wire axis. It has been found that the energy gap Eg in the Bi-17 at % Sb wires increases with decreasing wire diameter as 1/d, which is a manifestation of the quantum size effect. At low temperatures, a deviation from the exponential temperature dependence of the resistance R ~ exp (E/2kBT) is observed; the conductivity of the wires increases with decreasing diameter which is most pronounced at Т = 4.2 К due to the TI properties, in particular, the presence of surface states with high conductivity. The effect of temperature, magnetic field, elastic deformation, and the diameter of the Bi-17 at % Sb wires on power factor P.f. = α2σ in the temperature range of 4.2 – 300 K has been studied. It has been shown that the maximum P.f. value is achieved at T = 300 K for wires with d = 100 nm and P.f. decreases with increasing diameter d. It has been found that both the magnetic field (H // I) and the elastic deformation of the wires lead to increase in the power factor by 35 – 40 % at T > 150 K; this finding opens up the possibility of optimizing the thermoelectric parameters of Bi1-xSbx TI based wires for use in thermoelectric energy converters.