新穎BiTe(Sb,Se)基熱電薄膜---三維可調控高方向性奈米結構、金屬奈米粒子介面修飾與高效能薄膜型熱電轉換元件

Abstract

熱電材料具有尺寸小、結構簡單、可靠度高之特點，且可以作為發電或致冷器之用途，但由於傳 統塊材之熱電轉換效率過低，因而使其應用受到極大之限制。近年來由於奈米科技的發展，透過各種 奈米結構之合成或介面改質技術，使得熱電材料轉換效率在近年來大幅提升，部分熱電材料系統已達 商業應用之要求。根據相關理論計算及重要實驗成果可知，熱電材料之ZT 值與內部結構之「尺度」、 「維度」以及「方向性」高度相關。因此，本研究主要是利用三個維度結構參數之控制，合成新穎熱 電薄膜，來達到提昇熱電材料ZT 值之目的。其內容包括三大主題：三維可調控高方向性BiTe (Sb, Se) 基奈米結構熱電薄膜、金屬奈米粒子介面修飾與高效能薄膜型熱電轉換元件。 本研究主要利用Nd：YAG 脈衝雷射沉積技術(Nd:YAG pulsed laser deposition, Nd:YAG PLD)，製 備包括零維、一維、二維、三維之全新Bi-Te(Sb, Se)基奈米結構熱電薄膜。此外，本研究擬利用斜向 沉積(glancing angle deposition; GLAD)技術技術，更進一步製備各種維度之高方向性BiTe (Sb, Se)基熱 電薄膜。藉由調控鍍源與基板之角度，可獲各類不同傾斜角度、間距及多孔性之奈米結構。藉由此 熱電結構薄膜之奈米尺度化、低維度化、高方向性化，探討各種結構組合對熱電性質之影響，並與 理論計算相互印証。另外，本研究更將利用金屬奈米粒子介面改質技術，在Bi-Te(Sb, Se)基奈米結構 熱電薄膜中散佈鐵、鈷、鎳金屬奈米粒子，藉以提高奈米熱電薄膜之導電性質。最後，更將合成所 得之各維度高方向性n 型及p 型熱電薄膜，應用於高效能薄膜型熱電轉換元件之製作。

Thermoelectrics have very attractive features, such as small size, simplicity, and reliability, and have important applications for power generation or cooling. However, the low thermoelectric conversion efficiencies of conventional bulk materials limit their applications. Recently, due to the development of nanoscience and nanotechnology, the thermoelectric conversion efficiencies have been greatly improved by the nano-structured synthesis or interface modification techniques to meet the requirements for commercial use. According to the theoretical calculation and many experimental results, the thermoelectric properties extremely depend on the size, dimension, and directionality of structures. In this research plan, we thus expect to prepare unique thermoelectric films with high ZT by three-dimensional controlling depositions. Three main subjects are included: the fabrication of highly oriented nano-structured Sb/Se doped Bi-Te thin films, the metallic nanoparticle interface modification and their applications for high-performance thin-film thermoelectric conversion devices. First, special designed Nd:YAG pulsed laser deposition (PLD) is constructed for the synthesis of nano-structured Sb/Se doped Bi-Te thin films with dimensions from zero to three. In order to enhance the directional growth, high oriented nano-structured films, glancing angle deposition (GLAD) will be used for this purpose. The tilt-angle dependent directionality, spacing, and porosity will be optimized for the highest ZT and compared with the theoretical calculations. In addition, the Fe, Co and Ni metallic nanoparticles will be co-deposited with thermoelectric films for the improvement of electrical conductivity. Finally, the prepared n type and p type films will be applied for the fabrication of high performance of thermoelectric devices.