Temperature Dependences of the Galvanomagnetic Properties of $p-\text{Bi}_{2}\text{Te}_{3}$ Thermoelectric and Topological Insulator with Selenium Impurity

Abstract

Thermoelectric (TE) energy converters are widely used in modern science and technology, and areas of their application are being expanded. The Bi <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$2(\text{Te}_{1-\mathrm{X}}\text{Se}_{\mathrm{X}})_{3}$</tex> alloys are known as promising materials for TE cooling devices. Recently, interest in studying these materials has grown sharply due to the experimental evidence of their exhibiting special properties characteristic of 3D-topological insulators. Among the important characteristics determining TE efficiency and topological properties are the concentration and mobility of charge carriers. Thus, studying the galvanomagnetic properties of these materials is of great importance. The purpose of this work was to establish the effect of Te <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\rightarrow$</tex> Se substitution on the temperature dependences of the galvanomagnetic properties of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{Bi}_{2}\text{Te}_{3}$</tex> polycrystals. We measured the dependences of the Hall coefficient, electrical conductivity, and magnetoresistance on magnetic field <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(B=0.{0}1-1.\text{0T})$</tex> and temperature (80–295 K) for <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{Bi}_{2}(\text{Te}_{0.9}\text{Se}0.1)_{3}$</tex> polycrystal. We determined the boundary between a weak and strong magnetic fields. At 295 K, the studied polycrystal preserved p-type conductivity in the entire range of magnetic fields, but at 80 K, when magnetic field increased to <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$B=0.1\mathrm{T}$</tex> , an inversion of the conductivity type from <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$p$</tex> to <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$n$</tex> took place. The temperature dependences of the galvanomagnetic properties of the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{Bi}_{2}(\text{Te}_{0.9}\text{Se}_{0.1})_{3}$</tex> polycrystal exhibited more complex behavior as compared to <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{Bi}_{2}\text{Te}_{3}$</tex> , and in a strong magnetic field, an inversion of the conductivity type was registered. We attribute the observed effects to a complex defect structure of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{Bi}_{2}(\text{Te}_{0.9}\text{Se}_{0.1})_{3}$</tex> determined by the presence of charged defects of various types.