本研究中，在4.6 mTorr的真空度下通過150 ˚C、200 ˚C、300 ˚C、400 ˚C、500 ˚C和600 ˚C退火1小時，研究在具有鈦介層的矽（100）基板上所濺鍍的奈米雙晶銀薄膜之熱穩定性。鈦介層作為銀薄膜和矽基板之間的黏著層以減少晶格不匹配。首先，聚焦離子束(FIB)橫截面影像顯示濺鍍的銀薄膜主要是含有緻密雙晶邊界的柱狀結構，膜厚約1.8微米。此外，在鈦介層附近形成細晶粒過渡區。高解析X光繞射分析顯示，鍍著奈米雙晶銀薄膜具有高<111>優選方向，且(111)織構係數高達3.95 (織構係數等於4表示具有優選取向的晶粒;織構係數等於1表示具有隨機取向的晶粒)。電子背向散射繞射的反極圖(IPFM)顯示，樣品表面的晶粒幾乎為(111)面，這與X光繞射分析相符。(111)織構係數經過150 ˚C退火1小時保持不變。此外，發現部分柱狀晶粒向下成長以通過消耗細晶粒來降低總晶界能。令人著迷的是，薄膜在300 ˚C退火1小時後，包含許多完整的柱狀晶粒而沒有細晶粒，並且在晶粒生長過程中形成了{111}退火雙晶。通過ex situ FIB觀察，較高的退火溫度有利於奈米雙晶的向下成長。基於IPFM的結果表明，在退火溫度為400 ˚C時，表面局部出現了異常晶粒生長，(111)織構係數降低至3.39。然而，Ag (200)在500 ˚C和600 ˚C退火後成為主要的峰，這與FIB橫截面影像的觀察結果一致，高<111>優選方向的雙晶被(200)的粗大晶粒大量消耗。
其次，微結構的演變通常伴隨著薄膜性質的變化，在400 ˚C的退火溫度下，電阻率達到最低的1.79 μΩ-cm。理論上，在較高退火溫度下形成（200）粗晶粒由於電子散射的減少應使得電阻率最小。但是，從二次離子質譜儀（SIMS）的深度分佈圖中可以看出，矽確實在600 ℃的退火溫度下擴散到了銀膜層中，雜質矽對電子的高散射使薄膜電阻上升。
最後，我們將進一步研究退火溫度對薄膜性能（包括硬度和殘餘應力）的影響。另一方面，本文將詳細探討柱狀晶粒的向下生長機制和異常晶粒生長現象。

In this study, thermal stability of sputtered nanotwinned (nt) silver (Ag) thin film on (100) Si substrate with titanium (Ti) interlayer was investigated by annealing at 150 ˚C, 200 ˚C, 300 ˚C, 400 ˚C, 500 ˚C and 600 ˚C for 1 h under a vacuum of 4.6 mTorr, respectively. The Ti interlayer acts as an adhesion layer between the Ag film and Si substrate to reduce lattice mismatch. Firstly, focused ion beam (FIB) cross-sectional image showed that the sputtered nt-Ag thin film was mainly the columnar structures containing the dense twin boundaries. The film thickness was about 1.8 µm. Furthermore, the fine-grained transition zone was formed near the Ti interface. High-resolution X-ray diffraction (HRXRD) pattern showed the presence of highly <111>-preferred orientation in as-deposited nt-Ag thin film, and the (111) texture coefficient (TC) reached 3.95 (TC = 4 represents preferred-oriented crystallites; TC = 1 represents random-oriented crystallites). Inverse pole figure map (IPFM) of electron backscatter diffraction (EBSD) showed that the grains on the surface were almost (111) planes, which were consistent with the HRXRD analysis. The (111) TC remained unchanged after annealing at 150 ˚C for 1 h. Furthermore, it was found that partial columnar grains grew downward to reduce the total grain boundary energy by consuming the fine grains. Fascinatingly, the film contains many complete columnar grains without fine grains after annealing at 300 ℃ for 1 h with the formation of annealing {111} twins during grain growth. Higher the annealing temperature facilitates more downward growth of nanotwins by ex situ FIB observation. Based on IPFM results showing abnormal grain growth occurred on the local surface at annealing temperature of 400 ˚C, and (111) TC decreased to 3.39. However, Ag (200) becomes the dominant peak at 500 ˚C and 600 ˚C, which is consistent with cross-sectional FIB observation. The highly <111>-oriented twins are greatly consumed by the coarse-(200)-oriented grains.
Secondly, microstructural evolution is usually accompanied by changes in properties of thin film. At annealing temperature of 400 ˚C, the resistivity reached the lowest 1.79 μΩ-cm. Theoretically, the formation of (200) coarse grains at higher temperatures should minimize the resistivity due to the reduction of electron scattering. However, it can be seen from the secondary ion mass spectrometer (SIMS) depth profile that silicon has indeed diffused into the Ag film layer at annealing temperature of 600 ˚C, which the impurities of Si with high resistivity to electron scattering.
Finally, we will further study the effect of annealing temperatures on the properties of films, including hardness and residual stress. On the other hand, the downward growth mechanism of columnar grains and the phenomenon of abnormal grain growth will be discussed in detail in this thesis.

Abstract i
摘要 iii
致謝 v
Content vii
List of Figures ix
List of Tables xvi
Chapter 1 Introduction 1
Chapter 2 Literature Review 5
2.1 Advantages of forming nanoscale coherent Σ3 {111} twin boundaries 5
2.1.1 Ultrahigh Strength and excellent ductile 5
2.1.2 Extraordinary electrical conductivity 9
2.1.3 Stable in hardness during creep test 12
2.1.4 Radiation-tolerant 14
2.1.5 Electromigration resistance 19
2.1.6 Superior thermal stability 21
2.2 Methods for depositing nanotwinned film 23
2.2.1 Deformation twins and growth twins in Metals 26
2.2.2 Stacking Fault Energy 26
2.3 Formation of annealing {111} nanotwins in nanotwinned Ag films 31
2.4 Abnormal grain growth in nanotwinned Ag films 37
Chapter 3 Experimental Details 40
3.1 Coating process 40
3.2 Characterization Methods 42
3.2.1 Thermal Field Emission Scanning Electron Microscope (HRFEG-SEM) 42
3.2.2 Dual-beam Focused Ion Beam system (FIB/SEM) 42
3.2.3 X-ray Diffraction (XRD) 43
3.2.4 Electron Backscatter Diffraction (EBSD) 45
3.2.5 Time-of-Flight Secondary Ion Mass Spectrometer (ToF-SIMS) 46
3.3 Properties Measurements 52
3.3.1 Electrical resistivity 52
3.3.2 Hardness 53
3.3.3 Residual stress 55
Chapter 4 Results 61
4.1 Structural characteristics of as-deposited nt-Ag thin film by sputtering 61
4.2 Characterization analysis for the nt-Ag thin films during annealing process 69
4.2.1 Microstructural evolution of the nt-Ag thin films at different annealing temperatures 69
4.2.2 The grain orientation distribution and texture evolution on the nt-Ag thin films surface at different annealing temperatures 77
4.3 Annealing effect on the physical properties of nt-Ag thin films 81
4.3.1 Changing in resistivity of nt-Ag thin film during annealing 81
4.3.2 Changing in hardness and Young’s modulus of nt-Ag thin film during annealing 83
4.3.3 Changing in residual stress of nt-Ag thin film during annealing 88
Chapter 5 Discussion 93
5.1 Grain growth of nanotwinned silver thin films during the annealing process 93
5.1.1 The formation of annealing {111} twins during the downward growth of nt-Ag columnar grains below 400 ℃ annealing 93
5.1.2 Abnormal grain growth above 400 ℃ annealing 101
5.2 Effect of microstructural evolution on properties of nanotwinned Ag thin films during annealing 106
5.2.1 Electrical resistivity 106
5.2.2 Hardness 109
5.2.3 Residual stress 112
Chapter 6 Conclusions 114
Reference 116

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