Fabrication and Characterization of Electrodeposited Bismuth Telluride Films and Nanowires

To elucidate low-dimensional effects on thermoelectric materials, bismuth telluride film and nanowires array were fabricated by potentiostatically electrodeposition. Both materials are slightly Te-rich, n-type Bi2Te3, exhibiting preferred orientation in rhombohedral strcture. For both the Seebeck coefficient S approximate to -70 mu V/K at 300 K decreases linearly with decreasing temperature, showing a diffusive nature of current flow. The temperature dependence of resistivity (= I/sigma) of nanowires obtained from the data of a nanowires array and a single-nanowire reveals a better electric conductivity than that of the bulk. By coupling temperature-dependent thermal diffusivity and heat capacity data with a modified effective medium theory, a thermal conductivity kappa of 0.75 W/(m K) was obtained at 300 K. The ZT was calculated to be 0.45 at 300 K and 0.9 at 350 K for Bi2Te3 nanowires.