Grafting nanotechnology on thermoelectric materials leads to significant advances in their performance. Creation of structural defects including nano-inclusion and interfaces via nanostructuring achieves higher thermoelectric efficiencies. However, it is still challenging to optimize the nanostructure via conventional fabrication techniques. The thermal instability of nanostructures remains an issue in the reproducibility of fabrication processes and long-term stability during operation. This work presents a versatile strategy to create numerous interfaces in a thermoelectric material via an atomic-layer deposition (ALD) technique. An extremely thin ZnO layer was conformally formed via ALD over the Bi0.4Sb1.6Te3 powders, and numerous heterogeneous interfaces were generated from the formation of Bi0.4Sb1.6Te3–ZnO core–shell structures even after high-temperature sintering. The incorporation of ALD-grown ZnO into the Bi0.4Sb1.6Te3 matrix blocks phonon propagation and also provides tunability in electronic carrier density via impurity doping at the heterogeneous grain boundaries. The exquisite control in the ALD cycles provides a high thermoelectric performance of zT = 1.50 ± 0.15 (at 329–360 K). Specifically, ALD is an industry compatible technique that allows uniform and conformal coating over large quantities of powders. The study is promising in terms of the mass production of nanostructured thermoelectric materials with considerable improvements in performance via an industry compatible and reproducible route.

Interfaces, such as grain boundaries in a solid material, are excellent regions to explore novel properties that emerge as the result of local symmetry-breaking. For instance, at the interface of a layered-chalcogenide material, the potential reconfiguration of the atoms at the boundaries can lead to a significant modification of the electronic properties because of their complex atomic bonding structure. Here, we report the experimental observation of an electron source at 60° twin boundaries in Bi2Te3, a representative layered-chalcogenide material. First-principles calculations reveal that the modification of the interatomic distance at the 60° twin boundary to accommodate structural misfits can alter the electronic structure of Bi2Te3. The change in the electronic structure generates occupied states within the original bandgap in a favourable condition to create carriers and enlarges the density-of-states near the conduction band minimum. The present work provides insight into the various transport behaviours of thermoelectrics and topological insulators.

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The initial growth behavior of ZnO films by atomic layer deposition (ALD) on layer-structured Bi 2 Te 3 was investigated. Despite the lack of adsorption sites on the basal plane of Bi 2 Te 3 , negligible incubation in the ALD of ZnO on Bi 2 Te 3 was found in the temperature range from 100 to 160°C, and even the enhancement of the initial growth was observed at 200°C. We demonstrate that a ZnTe interfacial layer was formed in the early growth stage by the interaction between diethylzinc and Bi 2 Te 3 , which improved the nucleation of ZnO on the basal plane of Bi 2 Te 3 . These results indicate that surface modification via the interaction between a precursor and layer-structured materials is an efficient way to achieve fluent and uniform nucleation on layer-structured materials such as Bi 2 Te 3 .