Enhanced thermoelectric properties and superlattice structure of a Bi ₂Te₃/ZrB₂ film prepared by ion-beam-assisted deposition

In this study, it was found that a novel superlattice structure can favorably influence the carrier and phonon transport properties of superlattice films. The n-type Bi₂Te₃/ZrB₂ superlattice film was successfully fabricated by simple ion-beam-assisted deposition on a large scale. The composition and microstructure of the films were studied by X-ray diffraction, energy-dispersive X-ray spectroscopy, and scanning electron microscopy. The results show that the multilayered Bi₂Te ₃/ZrB₂ film with a modulation period (Λ) of 12 nm is alternately composed of monolithic Bi₂Te₃ and ZrB ₂ layers. The Bi₂Te₃/ZrB₂ superlattice film possesses a relatively rough interface and distinct layer structure. The thermoelectric properties, i.e., electrical conductivity (σ), Seebeck coefficient (S), and thermal conductivity (κ), of the Bi₂Te₃-based films were measured in the in-plane direction. The properties of the Bi₂Te₃/ZrB₂ superlattice film were greatly enhanced in comparison with those of Bi ₂Te₃ and ZrB₂ films. The superlattice Bi ₂Te₃/ZrB₂ film with a thermoelectric dimensionless figure-of-merit ZT = 1.54 was obtained at room temperature. An in-plane transport mechanism of the superlattice structure was proposed and investigated. Introduction of such a superlattice structure into films is therefore a very promising approach.