Ordered structure and high thermoelectric properties of Bi2(Te,Se)3 nanowire array

Abstract

In this paper, novel Bi2(Te,Se)3 nanowire array structure can favorably influence the carrier and phonon transport properties. The ternary compound n-type Bi2(Te,Se)3 film, composed of ordered nanowire array, has been successfully fabricated by a simple thermal co-evaporation technique without using any templates. The composition and the microstructure of the films are studied by x-ray diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive x-ray spectroscopy (EDX), and high resolution transmission electron microscopy (HRTEM). The results show that the nanowire array is composed of single-crystalline Bi2(Te,Se)3 nanowires with diameter of about 20nm. The well-oriented nanowires are parallel to each other and uniformly distributed. The growth mechanism of such nanostructure is proposed and investigated. The in-plane thermoelectric properties, i.e., electrical conductivity (σ) and Seebeck coefficient (S) and thermal conductivity (κ) of the nanowire array were measured. The properties of the well-oriented Bi2(Te,Se)3 nanowire array have been greatly enhanced in comparison with those of the ordinary Bi2(Te,Se)3 film. The Bi2(Te,Se)3 nanowire array film with a thermoelectric dimensionless figure-of-merit ZT=1.01 was obtained at room temperature. Introduction of such ordered nanowire array architecture into films is therefore a very promising approach.