Bi-Sb-Te奈米薄片之磁性傳導性質與西貝克係數; Magneto transport properties and Seebeck coefficient of thermoelectric material Bi-Sb-Te nanoplates

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題名:	Bi-Sb-Te奈米薄片之磁性傳導性質與西貝克係數;Magneto transport properties and Seebeck coefficient of thermoelectric material Bi-Sb-Te nanoplates
作者:	黃翊綺;Huang,Yi-Chi
貢獻者:	物理學系
關鍵詞:	拓樸絕緣體;熱電;磁阻;量子振盪;弱反局域;奈米薄片;西貝克係數;Sb2Te3;nanoplate;Seebeck coefficient;topological insulator;weak anti-localization;Shubnikov de-Hass oscillation;magneto resistance
日期:	2013-06-26
上傳時間:	2013-07-10 12:00:03 (UTC+8)
出版者:	國立中央大學
摘要:	我們藉由氣相沉積法成功生長出許多不同形狀，厚度約100-200 nm的Sb2Te3 與Bi0.5Sb1.5Te3 單晶奈米薄片。Sb2Te3 與Bi0.5Sb1.5Te3 是著名的熱電材料，我們已經量測到此種奈米結構下的西貝克係數 (Seebeck coefficient)。結果顯示Sb2Te3 與Bi0.5Sb1.5Te3 單晶奈米薄片在300 K下西貝克係數約為 90 μV/K 及325 μV/K。此外因為不同的樣品擁有不同的載子濃度進而費米能階也不同，我們將Sb2Te3 與Bi0.5Sb1.5Te3 連接起來量測不同方向的西貝克係數,以瞭解西貝克係數是否會隨著量測方向的不同而有所改變。結果顯示在250 K以上西貝克係數的差值約可達到23%。另一方面，Sb2Te3 化合物被測量及確定為擁有新型態材料的拓樸絕緣體 (Topological insulators)。由於一般拓樸絕緣體的文獻中樣品通常為塊材或薄膜樣品，單晶奈米薄片則較為少見。我們所生長的Sb2Te3單晶奈米薄片藉由外加磁場也同樣觀察到量子振盪 (Quantum oscillation) 以及弱反局域效應 (Weak anti-localization)。最後再藉由霍爾效應及磁阻的數據分析計算出Sb2Te3單晶奈米薄片的表面態是否為量子振盪現象中整個樣品傳導性的主要貢獻。我們的結果顯示樣品的內部塊材性質為整個樣品傳導性的主要貢獻。 Single crystalline nanoplates of Sb2Te3 and Bi0.5Sb1.5Te3 thermoelectric (TE) materials with thickness around 100-200 nm were successfully grown by a vacuum vapor phase deposition method. To compare with the bulk properties of these nanoplate specimens we have measured their electrical transports and Seebeck coefficients. The Seebeck coefficient of Sb2Te3 and Bi0.5Sb1.5Te3 nanoplates are about 90 μV/K and 325 μV/K at 300 K respectively, which are similar to those of the bulk. To answer the question “is there an asymmetry Seebeck coefficient along a sample consisting of two different TE materials with different carrier concentrations, such as Sb2Te3 and Bi0.5Sb1.5Te3. It was founded that the asymmetry Seebeck coefficient is about 23% at T>250 K. Since Sb2Te3 is experimentally and theoretically confirmed to be a topological insulator (TI) - a new surface state of condensed matter. Although intensive researches on TI materials have been carried out for past few years, the researches on single crystalline Sb2Te3 nanoplates are limited. In this thesis we report the observation weak anti-localization phenomena, and confirm the characteristic of topological insulators of Sb2Te3 nanoplates. Hall effect and magneto resistance data analysis provide a way to distinguish quantum oscillation contributed from the surface and bulk states in Sb2Te3 nanoplates. Experimental result shows the origin of quantum oscillation was mainly attributed to bulk electronic states.
顯示於類別:	[物理研究所] 博碩士論文

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