Nanostructural manipulations for achieving record-high room temperature figure of merit in the ZnSb thin films

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Recently, fabrication of high-efficiency miniature thermoelectric devices with thin films has attracted great attention. ZnSb-based thin films have been widely studied owing to their advantages of earth-abundant, eco-friendly, and excellent electron transport properties. However, its thermoelectric performance at room temperature is still low which extremely restricts its application. In this work, we report a high-power factor of 6.2 μWcm−1K−2 and a record-high thermoelectric figure of merit, ZT of 0.35 at room temperature from the non-stoichiometric ZnSb-based thin film, fabricated by a facile magnetron cosputtering technique. Extensive characterizations reveal that all the prepared films have a primary ZnSb phase with good crystallinity, leading to high electrical conductivity. Meanwhile, the carrier concentration is optimized with Zn addition, which contributes to a high Seebeck coefficient, resulting in a decent power factor. Simultaneously, the Zn-rich films also show nanopores, Zn-rich nanophases, and Zn4Sb3 nano inclusions. These induced nanostructures enhance the scattering of medium- and long-wavelength phonons, contributing to the reduction of lattice thermal conductivity. This work demonstrates that rational nanostructure manipulations can achieve high performance in ZnSb thin films, which possess potential applications for the fabrication of miniature thermoelectric devices.