量子點接面之熱電及熱整流的特性探討; Thermoelectric and Thermorectification Properties of Quantum Dot Junctions

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題名:	量子點接面之熱電及熱整流的特性探討;Thermoelectric and Thermorectification Properties of Quantum Dot Junctions
作者:	郭明庭
貢獻者:	電機工程學系
關鍵詞:	物理類
日期:	2010-08-01
上傳時間:	2011-07-14 10:12:57 (UTC+8)
出版者:	行政院國家科學委員會
摘要:	有鑑於能源短缺及全球暖化問題日趨嚴重，尋找豐沛的天然能源與開發有效的能源轉換技術成為眾所矚目且積極投入的重要課題。因此，如何善加利用熱，將之轉換成電能亦是值得努力嘗試的方向，亦即，熱電效應也是可以值得考量的重要能源轉換技術之一。不過由於塊材的熱電轉換效能非常低，導致傳統的熱電材料與元件無法提供有效的能源轉換。如今因奈米科技的快速發展，縮小材料維度所致的量子侷限效應，不僅可以大幅地增進光電轉換效率，更可以有效地壓低熱導率，進而提昇了熱力係數與熱電轉換效率(ZT)。由此可知，研究開發前瞻高效率奈米結構熱電材料不僅可以增進熱電致能的技術與應用，更可以擴展至冷/廢熱發電元件及系統，以達到節能/致能之終極目標。本理論計算研究討論的重點項目與工作分述如下： (1)利用多體理論來建立系統模型，並利用非平衡態格林函數來計算量子點介面系統的電流及熱流，進而決定在線性響應及非線性響應之電導值、熱力係數、熱導值及熱電係數，以利實驗量測及元件佈局，使其熱電係數值達到3以上。 (2)將找尋量子點介面系統在何種機制下可以具有方向性熱整流的特性.首先將檢驗雙量子點在於金屬電極非對稱耦合的情況下是否具有方向性熱整流的特性. 因方向性熱整流的特性是一種熱流對溫差的非線性響應,所以我們預測粒子交互作用是不可忽略的條件. Thermoelectric and thermo rectification properties of quantum dot junctions Due to energy and environment issues, it becomes important to understand the thermal properties of materials. Recently many efforts are to seek efficient thermoelectric materials because there exist potential applications of solid state thermal devices. Several methods were proposed to realize the enhancement of figure of merit (ZT) , one of them is to reduce system dimension. Nevertheless, ZT value higher than 3 has not been reported. Note that the highest ZT value is near 1 for conventional bulk material. System with ZT value larger than 3 can be applied to make home refrigerators replacing current compressor-based refrigerators. In addition, allow it apply to electrical power generators. We study the thermoelectric properties of multiple QDs embedded into an insulator matrix, which is proposed for realizing solid state refrigerators or electrical generators. The solid state refrigerators (electrical generators) need to remove (generate) large amounts of heat (current). Consequently, the high QD density is required for realistic applications. For the high QD density system, we need to consider the multiple energy level Anderson model due to the interdot Coulomb interactions and electron hopping effects. This work has two purposes. In the linear regime we attempt to clarify how the proximity effect influences the ZT values in the Coulomb blockade regime. The electrical conductance, thermal conductance, thermal power and figure of merit (ZT) of quantum dot junction system are theoretically investigated The charge and heat currents in the sequence tunneling process are calculated by the Keldysh Green function technique. How the inelastic scattering effect arising from size fluctuations, defects and electron-phonon interactions influence ZT values are also include in the first-year work. Because the nonlinear response has the crucial applications of thermal devices such as thermal diodes and transistors. We would like to examine and look for if the double dots junction system act as a thermal rectifier in the second year work. 研究期間：9908 ~ 10007
關聯:	財團法人國家實驗研究院科技政策研究與資訊中心
顯示於類別:	[電機工程學系] 研究計畫

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