拓樸絕緣體因為它特殊的量子態近來已成為一個繼石墨烯之後之一重要領域，同時，因為它在兆赫波、自旋電子的應用潛力，近幾年來更是吸引大量的研究熱潮。鉍系拓樸絕緣體(Bi2Se3, Bi2Te3…)是早已存在且成長技術成熟的熱電材料，然而在其數奈米薄膜結構中，卻依然在元素結構和載子特性方面有著許多未知的特性。本篇論文中，我們利用超快激發-探測技術探討鉍系拓樸絕緣體薄膜的超快光電子學特性。首先，我們報導了Bi2Se3、Bi2Te3薄膜中谷間散射的行為，這是首次在可排除表面態貢獻下對塊材態的觀察;其次，我們研究了同調聲子在拓樸絕緣體的行為，首次觀察到過往文獻預期在小於特定厚度不會存在的同調聲子振盪，塊材態與表面態的競爭也經於吸收特性被報導；最後，透過數值分析結合量測結果，我們對同調聲子振盪生命期的可能機制做了相關的說明。

Topological insulators have been attracted lots of attentions due to their potential in spintronics which is attributed to special surface state from strong spin orbital interaction. To date, plenty of researches about topological insulators have been reported. However, most investigations focus on physical properties of single crystals. As a result, studies in detail to topological insulator thin film, such as grown by molecular beam epitaxy (MBE), are very important problems and in an urgent need.
In this thesis, ultrafast dynamics of MBE growth Bi2Se3 and Bi2Te3 thin films with various thickness(3-15nm).
First, we report the transient reflectivity of Bi2Se3 and Bi2Te3 thin films using Optical pump Mid-infrared probe spectroscopy (OPMP) and Optical pump Optical probe spectroscopy (OPOP). By adjusting the wavelength of probe beam wavelength, different dynamics behaviors were observed. This is attribute to different contribution of surface state as various probe wavelength. The corresponding relaxation time(2~11ps) constants of bulk states are fulfilled with the reported values. Clear power dependent relaxation time, increasing from 2 to 11ps as increasing pump fluence from 1.52 to 12.13uJ/cm2, was observed and explained by inter-valley scattering effect of excited bulk state. This is first time for our best knowledge that we can investigate the dynamics of bulk state independently in topological insulators.
Additionally, we investigate the coherent phonon properties within the Bi2Se3 and Bi2Te3 films. Using Optical Pump Optical Probe Transmitted spectroscopy (OPOPT), the oscillation phenomenon were observed within the pump probe profile. This can be attribute to coherent phonon which has been discussed theoretically and predicted that the coherent phonon will be un-exist for topological insulator with thickness less than 20nm for Bi2Te3 and 40nm for Bi2Se3, respectively. Possible mechanism, thickness dependent coherent phonon life time and competition between bulk state and surface state are discussed as well.

論文審書．．．．．．．．．．．．．．．．．．．．．．．．．．．．i
致謝．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．iii
摘要．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．iv
英文摘要．．．．．．．．．．．．．．．．．．．．．．．．．．．．v
第一章 續論．．．．．．．．．．．．．．．．．．．．．．．．．．1
1.1 前言．．．．．．．．．．．．．．．．．．．．．．．．．．．1
1.2 研究動機．．．．．．．．．．．．．．．．．．．．．．．．．2
1.3 論文架構．．．．．．．．．．．．．．．．．．．．．．．．．3
第二章 拓樸絕緣體與超快雷射激發-探測光譜系統．．．．．．．．．．4
2.1 拓樸絕緣體．．．．．．．．．．．．．．．．．．．．．．．．4
2.1.1. 拓樸絕緣體之概述．．．．．．．．．．．．．．．．．．．．．4
2.1.2. 拓樸絕緣體之能帶結構．．．．．．．．．．．．．．．．．．．5
2.1.3. 三維拓樸絕緣體-硒化鉍、銻化鉍的之原子架構及能帶結構．．．9
2.1.4. 拓樸絕緣體的應用．．．．．．．．．．．．．．．．．．．　13
2.2 超快雷射激發-探測光譜系統．．．．．．．．．．．．．．．．15
2.2.1. 超快雷射激發-探測光譜系統原理．．．．．．．．．．．．． 15
2.2.2. 自相關系統、脈衝寬度與系統解析度．．．．．．．．．．．．． 19
2.2.3. 時間解析近紅外反射式、穿透式激發-探測光譜系統架構．．．．．24
2.2.4. 時間解析反射式近紅外光激發-中紅外光探測光譜系統架構．．．．28
第三章 薄膜拓樸絕緣體之反射式近紅外激發-中紅外探測光譜與傅立葉轉換
紅外光譜及其超快載子動力學研究．．．．．．．．．．．．．． 31
3.1 薄膜拓樸絕緣體之反射式近紅外激發-中紅外探測系統(OPMP)光譜．31
3.1.1. 實驗樣品條件與參數．．．．．．．．．．．．．．．．．．．． 31
3.1.2. 實驗結果與分析．．．．．．．．．．．．．．．．．．．．．． 32
3.2 薄膜拓樸絕緣體之傅立葉轉換紅外光譜(FTIR)．．．．．．．．．． 39
3.2.1. 實驗儀器與架構．．．．．．．．．．．．．．．．．．．．．． 39
3.2.2. 實驗結果與分析．．．．．．．．．．．．．．．．．．．．．． 41
3.3 結論．．．．．．．．．．．．．．．．．．．．．．．．．．． 43
第四章 薄膜拓樸絕緣體之反射式近紅外激發-探測光譜及其超快載子動力學
研究．．．．．．．．．．．．．．．．．．．．．．．．．．．．47
4.1 薄膜拓樸絕緣體之反射式近紅外激發-探測系統(OPOPR)光譜．．． 47
4.1.1. 實驗樣品條件與參數．．．．．．．．．．．．．．．．．．．． 47
4.1.2. 實驗結果與分析．．．．．．．．．．．．．．．．．．．．．． 48
4.2 結論．．．．．．．．．．．．．．．．．．．．．．．．．．． 53
第五章 薄膜拓樸絕緣體之穿透式近紅外激發-探測光譜及其超快載子、聲子
動力學研究．．．．．．．．．．．．．．．．．．．．．．．．．55
5.1 薄膜拓樸絕緣體之穿透式近紅外激發-探測系統(OPOPT)光譜．．． 55
5.1.1. 實驗樣品條件與參數．．．．．．．．．．．．．．．．．．．． 55
5.1.2. 實驗結果與分析．．．．．．．．．．．．．．．．．．．．．． 56
5.2 薄膜拓樸絕緣體的聲子振盪行為．．．．．．．．．．．．．．． 64
5.2.1. 拓樸絕緣體的聲子振盪行為．．．．．．．．．．．．．．．．． 65
5.2.2. 由穿透式近紅外-激發探測光譜觀察薄膜拓樸絕緣體之聲子振盪行為
、種類及其頻率分析．．．．．．．．．．．．．．．．．．．．． 68
5.2.3. 薄膜結構內部之聲子特性分析．．．．．．．．．．．．．．．． 74
5.3 結論．．．．．．．．．．．．．．．．．．．．．．．．．．． 80
第六章 結論與未來展望．．．．．．．．．．．．．．．．．．．．．．．82
6.1 結論．．．．．．．．．．．．．．．．．．．．．．．．．．． 82
6.2 未來展望．．．．．．．．．．．．．．．．．．．．．．．．． 83
參考文獻．．．．．．．．．．．．．．．．．．．．．．．．．．．．． 84

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