Thermoelectric Properties of Quantum Bi Wire Doped with Sn at Electron Topological Transitions Induced by Stretch and Doping

摘要

The work is devoted to investigation of thermopower and magneto-thermopower in the longitudinal field in wires of pure Bi and Bi alloys with concentrations of T-holes at 4.2K up to 3*10¹⁸ cm^-3. The diameters of wires change from 100 nm to 3μ. Bi and Bi wires (in glass cower) were fabricated by casting method from liquid phase. All wires had the same orientation - wire axis make up and angle of 20° with the bisector axis CS in the bisector trigonal plane. Peculiarities of thermopower and resistance behavior caused by electron topological transitions (ETT) induced by stretch and doping are found. ETT were fixed by change of the Fermi surface cross-section detected by the ShdH oscillations on both resistance and thermopower. It is shown that the positive peak in the temperature dependence thermoelectric power α and power factor P.f.=α²σ in nanowires of pure Bi, observed at ～40K, is shifted in area of higher temperatures with growing Sn concentration. At low temperatures the singularities in the thermopower and resistance at ETT induced by extension are significantly different for the cases, when the Fermi level ε_F is located in the conduction band or in the valence band of light L holes. Thus, in the first case the electron input increases with extension, but in the second case the hole one increases, i.e. the positive thermopower value becomes greater.