Electrical transport properties of single-crystal Bi1-xSbx micro-and nanowires in semimetal and semiconductor states

Abstract

We report an investigation of the electrical transport properties, thermoelectric properties, the Shubnikov de Haas (SdH) oscillations of single crystal Bi1-xSbx, micro and nanowires in semimetal and semiconductor states. It is shown that the quantum size effect (QSE) occurs in the Bi-2at%Sb wires with diameter 4-5 times larger, than in pure Bi wires:- semimetal - semiconductor transition in Bi1-xSbx nanowires manifested in the “semiconductor” temperature dependences of resistance R(T) at diameter ≤ 400 nm;- the change in sign of thermopower at temperature less, than in pure Bi;- the occurrence of the negative magnetoresistance in a transverse magnetic field (H // C2 and H // C3) takes place at d < 400 nm. From SdH oscillations we find the carrier mobility from light L-electrons µe=(80-100)*103 cm2/Vs in Bi-2at%Sb wires at 4,2 K, that testifies to high structural perfection of investigated nanowires. In Bi-3at%Sb foils SdH oscillations were observed only in directions H I. Semiconductor Bi1-xSbx nanowires show the temperature activated dependence R(T) and the growth of the energy gap with decreasing wire diameter due the quantum size effect. The sharp deviation from the exponential dependence R(T) and SdH oscillations at low temperatures observed in thinner semiconductor Bi1-xSbx nanowires are interpreted in terms of the surface state in topological insulators, through a spin-orbital Rashba interaction in the surface TI. Power factor dependence on the wires diameter, temperature, magnitude and magnetic field direction were calculated.