Enhancement of thermoelectric properties induced by oriented nanolayer in Bi₂Te_2.7Se_0.3 columnar films

In this paper, it was found that layered and columnar structure can favorably influence the carrier and phonon transport properties of films. The n-Bi₂Te_2.7Se_0.3 columnar film with layered structure was successfully achieved by simple magnetron co-sputtering method at 400°C deposition temperature, due to the more sufficient growth along the in-plane direction induced by the enhanced mobility of deposited atoms. The layered nanostructure is clear with each layer <25 nm in the columnar film. The properties of the Bi₂Te_2.7Se_0.3 columnar film with layered structure were greatly enhanced in comparison with those of the columnar and the ordinary films synthesized respectively at 350°C and 250°C deposition temperature. The layered Bi₂Te _2.7Se_0.3 columnar film with a thermoelectric dimensionless figure-of-merit ZT = 1.27 was obtained at room temperature. The layered column structure was the main reason for the properties enhancement observed in the Bi₂Te_2.7Se_0.3 film. Introduction of such uniquely layered and columnar structure into thermoelectric films is therefore a very promising approach.