具抗反射及疏水特性之奈米結構表面設計與先導性製程研究

Design and Preliminary Fabrication of Nanostructured Surface for Anti-reflective and Hydrophobic Effect

張祐嘉(You-Chia Chang)

指導教授 ： 李世光

國立臺灣大學/工學院/應用力學研究所/碩士(2004年)

https://doi.org/10.6342/NTU.2004.00593

摘要

包含蓮葉在內的某些具有結構之表面展現出非常特別的可溼性。這些的表面的接觸角大於140度，因些被稱超疏水表面。它們最引人注目的是所謂的自清潔效應。另一方面，有另一類的具結構表面展現出抗反射的效果。而這一類的表面，其結構必須是週期性的並且在次波長這一個等級。
本論文中，我們提出了一個新的想法，認為因為它們都是由表面結構造成的，所以抗反射和超疏水的特性是可以被結合在一起的。這樣的結合能產生許多新的應用。例如，具有自清潔性的抗反射表面可以用在太陽能電池上來改善效率。而透明的超疏水表面可以用於汽車的擋風玻璃或是窗戶上。
根據次波長結構光學及可溼性的知識，我們認為若在本身為疏水的材料上設計外形為連續的次波長週期結構，將可望結合這兩個效應。其中我們使用等效折射率理論和嚴格耦合波理論來分析抗反射的行為，而可溼性則利用最小總表面能的方法進行分析。
實驗上，我們採用全像微影術、電漿蝕刻以及旋鍍鐵氟龍的方式來製作試片，並量測該試片的反射頻譜和接觸角。在本論文中製作的結構，量測到的頻譜和模擬有一定的吻合度。雖然在規則的一維結構上，我們並未觀測到超疏水現象，但卻在過度蝕刻的不規則一維結構上成功地觀察到。我們從實驗結果推論，認為一維結構並不適合結合抗反射及超疏水效應。但實驗顯示適當的二維結構很有可能達成這兩個效應的結合。

關鍵字

抗反射 ； 超疏水表面 ； 蓮花效應 ； 次波長結構

並列摘要

Some structured surfaces such as lotus leaves show very special wettability behavior. They are called super-hydrophobic surfaces since the contact angles exceed 140 degree. Most attractive property of super-hydrophobic surface is the self-cleaning effect. On the other hand, there is another group of structured surfaces which shows antireflective (AR) effect. For this kind of surfaces, the structure is periodic and at subwavelength scale.
In this thesis, we propose a new idea – the AR and super-hydrophobic effects can be combined together since they both attribute to the existence of surface structure. The combination can produce new applications. For example, a “self-cleaning” AR surface can be used on solar cells to improve efficiency. A “transparent” super-hydrophobic surface can be made on windshields or windows.
From the knowledge of subwavelength optics and wettability, we conclude that the combination is possible by imparting a periodic subwavelength structure with continuous profile to an intrinsically hydrophobic material. The AR behavior is analyzed by effective medium theory (EMT) and rigorous coupled-wave approach (RCWA). The wettability is analyzed by minimizing the total surface energy.
We fabricate desired structured surfaces by holographic lithography, plasma etching and Teflon coating. The performance is evaluated by measuring the reflectance spectrum and contact angle. For the 1D structure fabricated in this thesis, the measured reflectance spectrum matches the simulation. Although super-hydrophobic effect is not observed on regular 1D structure, it is observed super-hydrophobicity on over-etched irregular 1D structure. We conclude from experimental results that 1D structure is not suitable for the combination of AR and super-hydrophobic effects. The experiment indicates the combination is very promising by proper 2D structures.

並列關鍵字

lotus effect ； subwavelength structure ； super-hydrophobic surface ； antireflection

參考文獻

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