在本篇論文中，透過低溫與多脈衝的同調聲子激發－探測系統，我們深入探討拓譜絕緣體薄膜的聲子動力學。首先，我們利用溫控瞬時激發－探測光譜系統(78K~290K)研究在不同溫度下的聲子行為，除了再次確認在薄膜拓譜絕緣中同調聲子的存在外，並提出表面態吸收主導對反射汞探實驗的影響已解釋之前文獻說明沒辦法在室溫下觀察到同調聲子的機制；我們更在低溫環境下(78K、90K)發現到四種不同的聲子行為(A1g1、A1g2、Eg2、coherent acoustic phonon)同時出現，利用梯度力的變化，聲子特性以及耦合效率的溫度變化依存性可以被解釋；此外，我們實驗室首次觀測並測量出聲子Eg2模態的生命週期為2.87ps。在藉由雙脈衝的瞬時激發－探測光譜系統來調控聲子的訊號大小，透過聲子A1g1模態的共振，來放大訊號，我們能夠更好的分析聲子A1g模態在材料內部的行為，該方法也提供解釋反射光譜結果中聲子行為來源的可能機制。

In this thesis, temperature-dependent(78K~290K) coherent phonon dynamics in topological insulator Bi2Te3 are investigated by ultrafast pump-probe system. Four coherent phonon types(A1g1、A1g2、Eg2、coherent acoustic phonon) with strong temperature dependency are observed in transmission pump-probe spectroscopy at low temperature(78K、90K). These could be attributed to temperature dependent gradient force which resulting in the coherent phonons generation. Especially, lifetime of around 2.87ps for Eg2 phonon mode is observed for the first time. Additionally, A1g1 phonon oscillation in low temperature(78K~190K) reflectivity pump-probe spectroscopy is investigated. Unlike behavior in room temperature, A1g1 phonon oscillation is observed as the temperature cooling down to 90K. The depressing signal of reflective pump probe due to the enhancing absorption of surface state for thin film topological insulator will be accordingly increasing as temperature cooling is proposed.
Meanwhile, to enhance the weak A1g1 phonon signal in reflectivity pump-probe spectroscopy, technique of controlling coherent phonon is exploited by Michelson interferometer. The A1g1 phonon signal is successfully enhanced and with the almost same value of phonon lifetime taken from reflection or transmission pump probe measurement further confirm the nature of coherent phonon for thin film topological insulator. Finally, we discuss the possibility for investigating strength of phonon coupling using resonant coherent phonon technique as well.

第一章 緒論 1
1.1 前言 1
1.2 研究動機 2
1.3論文架構 3
第二章 拓樸絕緣體介紹 4
2.1 拓樸絕緣體之概述 4
2.2 拓樸絕緣體之能帶結構 6
2.3 三維拓樸絕緣體硒化鉍與碲化鉍之能帶結構與原子結構 10
2.4拓樸絕緣體之應用 12
2.5 拓樸絕緣體之聲子震盪行為 13
第三章 超快雷射激發－探測光譜系統 17
3.1 超快雷射激發－探測光譜系統原理介紹 17
3.2 系統解析度與脈衝寬度探討 21
3.2.1自相關系統介紹 22
3.3 溫控超快激發－探測光譜系統 26
3.3.1 溫控超快激發－探測光譜系統介紹 26
3.4多道脈衝超快激發－探測光譜系統 28
第四章 拓樸絕緣體薄膜在不同溫度下之超快載子動力學研究 30
4.1激發－探測光譜系統量測聲子行為之文獻探討與研究動機 31
4.2 實驗室工作結果回顧 33
4.2.1 瞬時反射式激發－探測光譜(OPOPR)結果回顧 34
4.2.2 瞬時穿透式激發－探測光譜(OPOPT)結果回顧 37
4.2.3 OPOPR與OPOPT總結與分析 41
4.2.4 反向探測瞬時反射式激發－探測光譜(BOPOPR)結果回顧 42
4.2.5 想法與討論 46
4.3 實驗條件參數與樣品參數 47
4.4 溫控瞬時激發－探測光譜結果與分析 48
4.4.1 溫控瞬時穿透式變化光譜結果 48
4.4.2 各種聲子模態間的關係與探討 59
4.4.3 瞬時反射式變化光譜結果 62
4.5 結論與探討 66
第五章 光控制拓樸絕緣體薄膜聲子震盪之超快動力學研究 67
5.1 瞬時多脈衝穿透式激發－探測光譜系統檢測 68
5.2 溫控瞬時多脈衝穿透式激發－探測光譜系統 71
5.3 溫控瞬時多脈衝反射式激發－探測光譜系統 74
5.4 結論與探討 77
第六章 結論與未來規劃 78
6.1 結論 78
6.2 未來展望 79
第七章 參考文獻 80

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