使用MBE成長碲化鉍薄膜於氧化鋁基板(0001)，並使用同步輻射光源(synchrotron radiation)角分析光電子能譜(ARPES)，X-ray光電子能譜(XPS)進行量測與分析，在固定基板溫度的情況下改變分子束流量比例(flux ratio)，以控制試片之化學成分，藉由XPS的分析計算得到試片組成之化學成分比例(Te/Bi ratio)，並由ARPES實驗中觀察到清晰的表面態(surface state)與狄拉克錐(Dirac cone)，並且實驗中觀察到藉由調整Te和Bi組成比例，參雜程度(doping level)隨著Te和Bi組成比例改變而跟著從n-型半導體往p-型演變。已知Bi2Te3晶體之一般電子特性通常是由電子施主(donors)所主宰而顯現出n-型半導體電性[7-11]，而狄拉克點(Dirac point)會深埋於費米能接之下，這使的難以表徵此拓樸絕緣體的電子傳輸(transport)性質，進而影響了應用特殊的狄拉克表面費米子特性之拓樸絕緣體元件的開發[12]。為了解決此問題可以利用異質(extrinsic)參雜與本質(intrinsic)參雜來解決。異質參雜舉例來說可利用0.67%的錫[13]或者是1%的鎘[14]，皆已被引入作為Bi2Te3之參雜元素，而本質參雜則可以藉由控制磊晶之條件而調整原子錯位缺陷(anti-site defect)的發生，來作為本質參雜。而藉由改變成長時之基板溫度(substrate temperature)來調整錯位缺陷產生的技術已經被成功演示[12]，本論文之工作嘗試以另一種方式來調整錯位缺陷之產生，藉由控制磊晶時分子束之流量比例(Te/Bi flux ratio)，來嘗試造成晶體結構中的原子錯位缺陷，並達成量的控制。

The epitaxial Bi2Te3 topological insulator (TI) thin films grown on sapphire (0001) by molecular beam epitaxy (MBE) were studied by using X-ray photoemission spectroscopy (XPS) and synchrotron radiation angle-resolved photoemission spectroscopy (ARPES). The Bi2Te3 films, grown at fixed substrate temperature with the different Te/Bi flux ratio for each samples, and used the XPS to calculate the chemical composition ratio. And sharp metallic states and Dirac cone were also observed by ARPES. Interestingly, we also observed that the doping level in Bi2Te3 films can be fine turned by varying the Te : Bi composition ratio systematically to form either p- or n-type films. The electronic properties of bulk Bi2Te3 crystals are usually dominated by electron donors, resulting in n-type conductivity. When the donors dominate, the Dirac point is buried deep below the Fermi level, which makes it difficult to characterize the topological transport properties and to develop topological devices that rely on the behavior of surface Dirac fermions. To compensate for the unintentional donors, a high-concentration of extrinsic dopants, for example, more than 0.67% Sn [13] or 1% Cd, [14] has been introduced into Bi2Te3. And the intrinsic doping is the other way, in principle, we can tuning the density of the anti-site defect by controlling the growth condition. The anti-site defect controlled by tuning the substrate temperature had been successfully demonstrated. In this work we tried another way to generate the anti-site defect, the variation of growth flux ratio(Te/Bi ratio) was tried to generate the atomic anti-site defect, and got the amount control.

Table of Contents
Abstract I
Acknowledgement III
Table of Contents IV
List of Figures V
Chapter 1 1
Introduction 1
Chapter 2 Theories and Principles 6
2.1. Molecular Beam Epitaxy (MBE) 6
2.1.1. Principle of Molecular Beam Epitaxy (MBE) 6
2.1.2. Multi-chamber UHV Growth /analytical System and off-site MBE Chamber 7
2.2. Photoelectron Spectroscopy 9
2.2.1 Introduction 9
2.2.2. Photoemission Process and Its Physical Meanings 10
2.2.3. Principle of Photoemission Spectroscopy 11
2.2.4. Features in the Photoemission Spectra 14
2.2.5. Analyze Depth of Photoemission Spectroscopy 15
2.3. In-situ XPS 17
2.4. Synchrotron Radiation ARPES 18
Chapter 3 Results and Discussion 20
3.1 Sample Preparation 20
3.2 The Choice of Protection Layer 21
3.3. XPS Measurement 24
3.3.1 Properties of Two Capping Materials 24
3.3.2 The Method of Chemical Composition Calculation by XPS 29
3.3.3. The Influence of Oxidation 32
3.4 ARPES Measurement Process 33
3.5. Comparison of XPS and ARPES 34
3.6. In-situ XPS and UPS measurement 36
3.6.1. UHV Portable chamber 36
Chepter 4 42
Conclusion 42
Reference 43

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