Order-induced improvement of thermoelectric properties in (Bi_0.2Sb_0.8)₂Te₃ column arrays

In this study, it was found that ordering of nanostructures creates some sort of channels that favor transport of carriers but hinder that of phonons. An oriented p-(Bi_0.2Sb_0.8)₂Te₃ column array film was successfully achieved by a simple thermal co-evaporation technique. This column array structure entailed columns with diameter of about 40 nm. The properties of the oriented (Bi_0.2Sb_0.8)₂Te₃ column array were greatly enhanced in comparison with those of the ordinary film. The (Bi_0.2Sb_0.8)₂Te₃ column array film with a thermoelectric dimensionless figureof- merit ZT = 1.17 was obtained at room temperature. The in-plane transport mechanisms of the ordered column array and the ordinary structures, and the lattice field model, were investigated and discussed. Ordering of column array was found to be the main reason accounting for the properties improvement observed in the (Bi_0.2Sb_0.8)₂Te₃ film. Introduction of such uniquely ordered column array structure into thermoelectric films is therefore a very promising approach.