隨著光電元件的需求越來越大，在當中扮演傳遞電子角色的電極勢必不可或缺。因此，對於此種透明導電電極，同時擁有高導電能力與高光學穿透成為一重要課題。近年來，因在可見光波段展現高光學穿透（80%）以及不錯的導電能力（片電阻約50 Ω/），銦錫氧化物玻璃被廣泛應用於顯示器與太陽能電池等光學元件。然而銦錫氧化物作為一金屬氧化物，其介電屬性大大限制了元件的導電能力，且氧化銦的能帶間轉換，使得光學穿透在354奈米波段以下大幅下降，更是阻斷了其在紫外光波段的光學應用。超穎材料基底透明導電電極具有可調控之光學響應、高導電以及良好的機械延展性等優點，已經在過去實驗室的論文當中被實現。在所有金屬材透明電極當中，銀在具備可見光高光學穿透和超高導電性的條件下，展現了比銦錫氧化物高出一倍的FoM（238），但也因銀本身較低的電漿子頻率(9.0 eV)和低波段的能帶間轉換(308 nm)，加上在多低端波激發出的電漿子共振，使其在藍光波段的表現較為尷尬。相反地，鋁因有較高電漿子頻率（12.5 eV）和能帶間轉換(800 nm)，使得鋁透明電極在和銀透明電極比較時，反而在藍光展現良好的光學穿透，在長波長則出現較大的損耗。在此篇論文中，我們的目標是透過將銀鋁熔煉為合金，期望合金能夠融合銀、鋁在它們優勢波段的光學性質，創造出銀鋁合金超穎透明電極，以實現在整個可見光、近紫外光的寬頻穿透。最後我們也成功在實驗中看到此融合趨勢。

Motivated by the increasing demand of optoelectronic devices, electrodes that play roles on providing vertical potential difference are indispensable. Thus, simultaneously performing high electric conductivity and high optical transmittance become a crucial issue for transparent conducting electrodes (TCE). In recent years, owing to its high average optical transmittance (80%) over the visible range and decent electrical conductivity (sheet resistance≈50 Ω/), Indium Tin Oxide (ITO) glass is widely used on optoelectronic application, including display and solar cell. However, the ceramic nature limits the highest figure of merit (FoM) it could reaches, and the applications are also prohibited in UV range as well due to its inter-band transition. Metamaterial-based transparent conducting electrodes composed of continuous metallic grid that posing advantages of tunable optical response, high electric conductivity and also mechanical flexibility have been proposed in previous works. Among all kinds of metallic materials, silver TCE performs highest FoM value up to 238, which is one time higher than that of ITO, due to its high electrical conductivity and high optical transmission in visible range. However, the low plasma frequency 9.0 eV and inter-band transition at 308 nm [1] make the performance of silver TCE embarrassed at shorter wavelength range, moreover, localized surface polariton resonance excited at blue light region causes severe optical dissipation, and it is more intensive as the periodicity of metallic grid goes down. On the other hand, high plasma frequency (12.5 eV) and high inter-band transition (800 nm) make aluminum TCE demonstrate the opposite trend of transmittance spectrum, exhibiting excellent optical properties in blue light wavelength range and even UV range, when it is compared to silver one. Therefore, in this work, we aim to combine their optical properties at their dominating wavelength range by melting silver and aluminum together and creating silver-aluminum alloy metamaterial-based transparent conducting electrode, in order to revise and balance the optical transmittance of sub-wavelength TCE, and fulfill broadband transmission that can be applied on corelated applications.

摘要………………………………………………………………………………ii
Abstract…………………………………………………………………………..iv
Acknowledgements………………………………………………………………vi
List of Figures…………………………………………………………………..viii
List of Tables…….……………………………………………………………....xv
Content………………………………………………………………………….xvi
Chapter 1: Introduction….. ……………………………………………………….1
Chapter 2: Literature review………………………………………………………5
2.1 Transparent conducting electrodes……………………………………………..5
2.1.1 Figure of merit (FoM)………………………………………………….....5
2.1.2 Transparent conducting oxides (TCOs) …………………………...…………8
2.1.3 Graphene-based electrodes………………………………………...…….12
2.1.4 Metallic nanowires electrodes…………………………………………….14
2.1.5 Metallic nanowire network electrodes……………………………………...18
2.1.6 Comparison of different transparent conducting electrodes……………………..22
2.2 Metamaterial-based metallic grid TCE………………………………………...24
2.2.1 Drude Lorentz dispersion model…………………………………………..24
2.2.2 Subwavelength plasmonic effects…………………….…………………...30
2.2.3 Metallic material selection……………………………………………….38
Chapter 3: Design and simulation………………………………………………..46
3.1 Transmittance simulation……………………………………………………46
3.1.1 Silver simulated results………………………………………………….48
3.1.2 Aluminum simulated results……………………………………………...58
3.2 Figure of merit calculation…………………………………………………...64
3.3 Transmittance comparison between different TCEs……………………………..68
Chapter 4: Alloy preparation and optimization…..………………………………71
4.1 Alloy preparation…………………………………………………………...71
4.2 X-ray photoemission spectroscopy analysis……………………………………73
4.3 X-ray diffractometer analysis……………………………………………...…78
4.4 Ellipsometry measurement…………………………………………………..82
Chapter 5: Fabrication…………………………………………………………...88
5.1 Process flow……………………………………………………………….88
5.2 Electron beam lithography…………………………………………………...89
5.3 Electron beam evaporation…………………………………………………..93
Chapter 6: Results and discussions..……………………………………………..97
6.1 Transmittance measurement setup…………………………………………….97
6.2 Measured transmittance results……………………………………………….99
6.3 Sheet resistance measurement………………………………………………106
Chapter 7: Conclusion………………………………………………………….112
Reference……………………………………………………………………….114

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