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

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.