Multilayered structure and enhanced thermoelectric properties of Bi1.5 Sb0.5 Te3 film with preferential growth.

In this paper, uniquely (0 1 5)-preferential growth plane and alternating stress field can favorably influence the carrier and phonon transport properties of multilayered films. The p-type Bi1.5Sb0.5Te3 multilayered film has been successfully fabricated by a simple thermal co-evaporation technique. The composition, microstructure, and in-plane thermoelectric (TE) properties of films have been characterized and measured, respectively. The measurement results show that the multilayered Bi1.5Sb0.5Te3 film is (0 1 5)-preferential growth. The multilayered structure film is composed of the (0 1 5)-oriented and the ordinary nanolayers. The properties of the multilayered Bi1.5Sb0.5Te3 film has been significantly enhanced in comparison with those of the highly (0 1 5)-oriented and the ordinary Bi1.5Sb0.5Te3 films. The multilayered Bi1.5Sb0.5Te3 film with a TE dimensionless figure-of-merit ZT = 1.28 was obtained at room temperature. The transport mechanism of multilayered structure is proposed and investigated. The internal strain field and (0 1 5)-preferential growth plane are the main reasons for the properties enhancement observed in the multilayered Bi1.5Sb0.5Te3 film. Introduction of such uniquely (0 1 5)-preferential growth plane and alternating stress field into TE films is therefore a very promising approach. [ABSTRACT FROM AUTHOR]