Thermoelectric superlattices are expected to decouple the strong correlation between various thermoelectric parameters, and are an important strategy for excellent thermoelectric performances. The superlattices of (Bi)(BiTe) homologous series are well-known for low lattice thermal conductivity and intriguing topological surface states. However, the impacts of electronic structure on the thermoelectric performance were still not well-understood in (Bi)(BiTe). To cope with this issue, BiBiTe superlattice-like films with adjustable Bi/(Bi+BiTe) molar ratio () were successfully fabricated by the molecular beam epitaxy technique. Angle-resolved photoemission spectroscopy measurements combined with theoretical calculations revealed the conduction band evolution from single-valley to multi-valley as ≥ 0.30, leading to intrinsically high carrier effective mass and improved thermoelectric power factor. Also, the superlattice film ( = 0.46) with the structure close to BiTe possesses the topological surface state feature around the high symmetry point. As a result of the high effective mass of 3.9 and very high electron density of 2.31 × 10 cm, the film with = 0.46 acquired the highest power factor of 1.49 mW·m·K at 420 K, outperforming that of other (Bi)(BiTe) superlattices. This work lays an essential foundation on understanding the electronic structure and further improving thermoelectric performances of (Bi)(BiTe) homologous series.

中文翻译：

---

n型Bi2[sbnd]Bi2Te3超晶格薄膜的本质大有效质量和多谷带特性

热电超晶格有望解耦各种热电参数之间的强相关性，是获得优异热电性能的重要策略。 (Bi)(BiTe)同系超晶格以其低晶格热导率和有趣的拓扑表面态而闻名。然而，(Bi)(BiTe)中电子结构对热电性能的影响仍不清楚。为了解决这个问题，通过分子束外延技术成功制备了具有可调节Bi/(Bi+BiTe)摩尔比()的BiBiTe超晶格薄膜。角分辨光电子能谱测量与理论计算相结合，揭示了导带从单谷到多谷的演变≥0.30，从而导致本质上高的载流子有效质量和改进的热电功率因数。此外，结构接近BiTe的超晶格薄膜（=0.46）具有高对称点周围的拓扑表面态特征。由于具有3.9的高有效质量和2.31 × 10 cm的极高电子密度，= 0.46的薄膜在420 K时获得了最高功率因数1.49 mW·m·K，优于其他(Bi)( BiTe）超晶格。该工作为理解(Bi)(BiTe)同系物的电子结构和进一步提高热电性能奠定了重要基础。