Germanium Telluride (GeTe) has been widely explored as a promising lead-free thermoelectric material in its rhombohedral and cubic phases. However, the structural transition between these two phases at ∼700 K causes an abrupt change of thermal expansion coefficient, challenging its broader practical applications. Also, as characterized by multi-valence bands and strong anharmonic interaction, the high-temperature cubic phase exhibits a higher power factor, lower thermal conductivity, and ultimately superior thermoelectric performance than its rhombohedral counterpart. Prompted by these, in this work, the cubic phase of Ge0.9Sb0.1Te (presented as GeSbTe in the following content) nanocrystalline thin film is successfully realized by RF sputtering followed by post-annealing treatment. Additionally, indium, as an electron donor to the germanium site and an effective scattering center, further moderates carrier concentration, enhances the Seebeck coefficient and reduces thermal conductivity. The optimal composition achieves an estimated peak zT of ∼1.95 and an estimated average zT of ∼1.11 within the temperature range of 300 K–575 K, showcasing GeTe as a compelling candidate for applications close to room temperature.

中文翻译：

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铟掺杂对立方 GeTe 基薄膜热电性能的协同效应


碲化锗 （GeTe） 作为一种很有前途的菱面体和立方相无铅热电材料已被广泛探索。然而，在 ∼700 K 时，这两个相之间的结构转变会导致热膨胀系数的突然变化，对其更广泛的实际应用提出了挑战。此外，由于具有多价带和强非谐相互作用的特点，高温立方相表现出比菱面体更高的功率因数、更低的热导率，并最终表现出卓越的热电性能。在此推动下，本工作通过射频溅射后退火处理成功实现了 Ge0.9Sb0.1Te 纳米晶薄膜的立方相（在以下内容中表示为 GeSbTe）。此外，铟作为锗位点的电子供体和有效的散射中心，进一步缓和载流子浓度，增强塞贝克系数并降低导热系数。在 300 K–575 K 的温度范围内，最佳成分实现了 ∼1.95 的估计峰值 zT 和 ∼1.11 的估计平均 zT，这表明 GeTe 是接近室温应用的令人信服的候选者。