Thermoelectric power factor of ternary single-crystalline Sb₂Te₃- and Bi₂Te₃-based nanowires

Nanowires of bismuth antimony telluride and bismuth telluride selenide (Bi15Sb29Te56 and Bi38Te55Se7) were grown by template-based pulsed electrodeposition. The composition and the crystallinity of the nanowires were determined by high-resolution transmission electron microscopy. The thermoelectric properties (Seebeck coefficient and electrical conductivity) of single p- and n-type nanowires, with diameter 80 nm and 200 nm, respectively, were determined as a function of temperature before and during heating in a helium atmosphere up to 300 K along the growth direction of the nanowires. After additional annealing in a tellurium atmosphere at 525 K, significantly enhanced transport properties are observed. Bulk-like power factors are achieved. In Bi38Te55Se7 nanowires, the Seebeck coefficients increase to -115 μV K(-1) and the thermoelectric power factors increase to 2820 μW K(-2) m(-1) at room temperature. In Bi15Sb29Te56 nanowires, Seebeck coefficients of up to S = +156 μV K(-1) and power factors of up to 1750 μW K(-2) m(-1) are obtained at room temperature.