Bismuth telluride (Bi₂Te₃) remains one of the most promising thermoelectric (TE) materials near room temperature due to its high figure of merit ZT. In this study, we present a systematic investigation of n-type Bi₂Te₃ (NBT) thin films deposited by thermal evaporation and subjected to post-annealing treatments at 50, 100, 150, and 200 °C in an inert N₂ atmosphere. X-ray diffraction (XRD) analyses show that annealing enhances crystallinity and increases average crystallite size from ∼18.5 nm (unannealed) to ∼34.2 nm (200 °C-annealed). Stylus profilometry confirms film thicknesses in the 290–320 nm range, while scanning electron microscopy (SEM) and three-dimensional surface measurements indicate a progressive smoothing and grain coalescence up to 150 °C, followed by slight roughening at 200 °C. Energy-dispersive X-ray (EDX) spectroscopy and elemental mapping reveal near-stoichiometric compositions with minimal elemental segregation, underscoring the effectiveness of post-annealing in preserving film uniformity. Hall measurements indicate that an annealing temperature of 150 °C yields the highest carrier concentration and mobility, correlating with the lowest resistivity and most pronounced negative Seebeck coefficient. Consequently, the film annealed at 150 °C exhibits the largest power factor (5.76 mW m⁻¹ K⁻²), surpassing literature-reported values for similarly prepared Bi₂Te₃ films. These findings demonstrate that carefully optimized thermal evaporation and moderate annealing temperatures significantly improve the TE properties of Bi₂Te₃ thin films, offering a scalable route to energy harvesting and cooling devices.

中文翻译：

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通过热蒸发和优化后退火增强 n 型 Bi₂Te₃ 薄膜的热电性能

碲化铋 （Bi₂Te₃） 由于其高品质因数 ZT，仍然是接近室温的最有前途的热电 （TE） 材料之一。在本研究中，我们系统研究了通过热蒸发沉积并在 50、100、150 和 200 °C 的惰性 N₂ 气氛中进行后退火处理的 n 型 Bi₂Te₃ （NBT） 薄膜。X 射线衍射 （XRD） 分析表明，退火可增强结晶度，并将平均晶粒尺寸从 ∼18.5 nm（未退火）增加到 ∼34.2 nm（200 °C 退火）。测针轮廓测量法确认了 290-320 nm 范围内的薄膜厚度，而扫描电子显微镜 （SEM） 和三维表面测量表明，在 150 °C 之前，逐渐平滑和晶粒聚结，然后在 200 °C 时略微粗糙化。 能量色散 X 射线 （EDX） 光谱和元素映射揭示了具有最小元素偏析的近化学计量成分，强调了后退火在保持薄膜均匀性方面的有效性。霍尔测量表明，150 °C 的退火温度会产生最高的载流子浓度和迁移率，这与最低的电阻率和最明显的负塞贝克系数相关。因此，在 150 °C 下退火的薄膜表现出最大的功率因数 （5.76 mW m⁻¹ K⁻²），超过了文献报道的类似制备的 Bi₂Te₃ 薄膜的值。这些发现表明，精心优化的热蒸发和适度的退火温度可显著改善 Bi₂Te₃ 薄膜的 TE 性能，为能量收集和冷却设备提供了一条可扩展的途径。