| 摘要: | 熱電材料能夠有效地將熱能轉換為電能，因此在廢熱回收和可持續能源應用方面極具潛力，因而備受關注。 其中, 薄膜熱電材料因其具有更高的能量轉換效率、適用於小型化和柔性裝置，以及與物聯網設備、可穿戴電子產品和廢熱回收系統等先進技術的兼容性，已成為重點應用領域。 基於碲化鍺 (GeTe) 的熱電材料因其高性能而脫穎而出，這歸功於其良好的電子特性、可調整的載流子濃度、結構的穩定性以及相穩定化的潛力。 作為一種無鉛熱電材料，GeTe 的斜方和立方相已被廣泛研究。 然而，由於熱膨脹係數的差異，GeTe 在大約 700 K 時會發生結構相變，這對於更廣泛的實際應用構成了挑戰。 將 GeTe 穩定在單一相，特別是具有優異電子特性和熱電性能的立方 相,將顯著提升其實用性。 本論文研究利用射頻 (RF) 濺射合成立方相 GeTe 薄膜，並通過後退火處理實現目標立方相。 為了進一步增強熱電性能，本論文引入了銦元素作為摻雜劑。研究通過全面的實驗與計算分析，探討銦摻雜對薄膜的結構、電子與熱電性能的影響。取代鍺位點的銦，增加了態密度有效質量，並作為散射中心，從而調節載子濃度、提高 Seebeck 系數並降低總熱導率。這些綜合效應顯著提升了材料的熱電性能，使得品質因數（zT）在約 575 K 時提升了約 4 倍。本研究展示了銦摻雜立方 GeTe 薄膜作為高性能熱電應用的一種有前景的候選材料，為可持續能源技術的進一步發展鋪平了道路。此外，在300 K至575 K的工作溫度範圍內，平均zT值提高了約3倍，這表明銦摻雜立方相GeSbTe薄膜在接近室溫的高性能熱電材料中具有潛力，為可持續能源技術的進一步發展鋪平了道路。;Thermoelectric materials have garnered significant attention due to their ability to efficiently convert heat into electricity, making them highly promising for waste heat recovery and sustainable energy applications. Among them, thin-film thermoelectrics have emerged as a key focus area, owing to their enhanced energy conversion efficiency, adaptability for miniaturized and flexible devices, and compatibility with advanced technologies such as IoT devices, wearable electronics, and waste heat recovery systems. Germanium Telluride (GeTe) - based thermoelectric materials stand out due to their high performance, attributed to favorable electronic properties, tunable carrier concentration, structural robustness, and the potential for phase stabilization. As a lead-free thermoelectric material, GeTe has been extensively studied in its rhombohedral and cubic phases. However, its structural phase transition at approximately 700 K, associated with differences in thermal expansion coefficients, poses challenges for broader practical applications. Stabilizing GeTe in a single phase, particularly the cubic phase, which exhibits superior electronic properties and thermoelectric performance, could significantly enhance its utility. This thesis investigates the synthesis of cubic phase GeTe-based thin films using radio frequency (RF) sputtering followed by post-annealing treatment to achieve the desired cubic phase. To further enhance the thermoelectric properties, indium was introduced as a dopant. Comprehensive experimental and computational studies were conducted to analyze the effects of indium doping on the structural, electronic, and thermoelectric properties of the films. Indium, substituting at the germanium site, increases the density of state effective mass and acts as a scattering center, thereby modulating carrier concentration, enhancing the Seebeck coefficient, and reducing total thermal conductivity. These combined effects led to a remarkable improvement in the thermoelectric performance of the material, resulting in approximately a 4-fold enhancement in the dimensionless figure-of-merit (zT) at around 575 K. Moreover an enhancement of ~3-fold in the average zT within the working temperature range of 300 K to 575 K suggest the potential of indium-doped cubic GeSbTe thin films as a promising candidate for high-performance near room temperature, paving the way for further advancements in sustainable energy technologies. |
