李世光臺灣大學：工程科學及海洋工程學研究所張德威Chang, Te-WeiTe-WeiChang2007-11-262018-06-282007-11-262018-06-282007http://ntur.lib.ntu.edu.tw//handle/246246/51015經由此本論文的系列研究，周期性漸變奈米結構表面在理論及實驗方面均證實其結合抗反射和親疏水性質之可行性。雖然至今此結構製作在透明基板的性質並未明瞭，但是此一設計主要之應用方面包括太陽能電池及戶外顯示面板之封裝等皆是以透明基板為基礎，因此設計和製作一維奈米結構於玻璃基板上乃成為本論文之主軸。 在抗反射及親疏水性質中，分別利用嚴格耦合波理論(RCWA)模擬及數值分析來設計奈米結構之外形，之後藉由電子束微影(e-beam lithography)和反應離子蝕刻(RIE)技術來定義以及轉印圖形至玻璃基板上，製程步驟完成後，經由量測證實此一設計同時具有抗反射及親疏水兩大性質。 除此之外在本研究中，發現許多有趣而且至今尚未完全明瞭之親疏水現象，包括異質性效應、非等向性現象和局部疏水性質，在此論文中將分析及驗證形成這些現象之初步原因，根據討論可知結構之幾何性質對液體之接觸角和擴散性質會有影響，此一概念發現在軟性電子中噴墨製程技術的液滴控制上將可有相當程度的應用潛力。After a series of research, feasibility of using periodic gradient nano-structured surface to integrate both the anti-reflection and the hydrophobic properties was proved both theoretically and experimentally. Up to this point, the underlying reason for these properties on transparent material is not completely clear even though most of the significant applications of this design are based on transparent materials, which includes package of solar cells and outdoor display panel, etc. Design and fabrication of one-dimensional nano-structures on glass substrate was thus adopted at the main platform to pursue basic understandings. Rigorous coupled-wave analysis (RCWA) and numerical computation were applied here to design the desired structure for anti-reflection and hydrophobic-hydrophilic properties respectively. Then definition and transferring of pattern are carried out by electron beam lithography and reactive ion etching (RIE) method respectively. After experimental confirmations, the newly designed structure was found to possess both anti-reflection and hydrophobic-hydrophilic properties. Besides that, some interesting but not clearly understood phenomena of wetability including heterogeneous effect, anisotropic effect and localized hydrophobic state have been found, analyzed and verified. According to these discussions contact angle and spreading property of liquid can be affected by geometry of surface structures. This idea may have great potential in droplet controlling of inkjet printing technique in flexible electronics in the future.謝 誌 i 摘 要 iii Abstract iv Content vi List of Figures x List of Tables xvi Chapter 1 Introduction 1 1.1 Motivation 1 1.2 Literature review 5 1.2.1 Super-hydrophobic property 5 Lotus effect 6 Artificial super-hydrophobic surface 7 Applications for super-hydrophobic surface 8 Trends 10 1.2.2 Contact angle hysteresis 12 Furmidge’s equation 13 Measurements of contact angle hysteresis 15 Relationships between wetability state and hysteresis 16 1.2.3 Anti-reflection effect 17 Traditional thin-film anti-reflection coating 19 Anti-reflection sub-wavelength structured surface 20 1.2.4 Super-hydrophobic anti-reflection surface 23 1.3 Thesis organization 24 Chapter 2 Theory 25 2.1 Theory of hydrophilic and hydrophobic properties 25 2.1.1 Surface tension 25 Minimization of total surface energy 27 Laplace’s law 29 2.1.2 Wetability 31 Young’s equation 32 Proof of Young’s equation by calculating minimization of total surface energy 33 2.1.3 Wetability on binary structured surface 37 Wenzel’s model 38 Cassie-Baxter’s model 39 Discussion of Wenzel’s and Cassie-Baxter’s models 40 2.1.4 Wetability on sinusoidal structured surface 42 2.2 Sub-wavelength optics 46 2.2.1 Optical approaches for different scales 46 Scalar theory 46 Treatment of roughness at atomic level 46 Optical issue at sub-wavelength scale 47 2.2.2 Effective medium theory (EMT) 49 Zero-order EMT for 1-D periodic structure 50 Conditions of applying EMT on sub-wavelength structure 53 Characteristics of EMT 55 2.2.3 Sub-wavelength gratings for anti-reflection 56 Binary sub-wavelength gratings 56 Continuous-profile sub-wavelength gratings 62 Chapter 3 Simulation and Calculation 66 3.1 Preliminary design 66 3.2 Simulations of anti-reflection property by RCWA 66 3.2.1 Transmission spectrum of glass substrate without structure 67 3.2.2 The effect of changing the period of nano-structure 70 3.2.3 The effect of changing the depth of nano-structure 78 3.3 Wetability calculation 82 Chapter 4 Experiment and Discussion 85 4.1 Fabrication of transparent nano-structured surface 86 4.1.1 Pattern definition by electron beam lithography 86 Area effect in electron beam lithography 90 Results 92 4.1.2 Pattern transferring by dry etching 96 Results and discussion 99 4.2 Measurement 101 4.2.1 Measurement of wetability 101 Results and discussion 101 4.2.2 Measurement of anti-reflection property 105 Results and discussion 106 4.3 Analysis and verification 109 4.3.1 Heterogeneous effect 109 4.3.2 Anisotropic phenomenon 112 4.3.3 Localized hydrophobic state on hydrophilic material 117 Changing droplet size 118 Changing period 119 Changing depth 120 Summary 121 Chapter 5 Conclusion 122 Chapter 6 Future Work 124 Improvement of nano-structure fabrication 124 Further verification 124 Large area fabrication 125 Multi-Scaled nano-structure 126 Appendix I 128 The WKB Approximation 128 Reference 1305355188 bytesapplication/pdfen-US親疏水抗反射蓮花效應奈米結構電子束微影製程液滴控制Anti-reflectionSuper-hydrophobicnano-structureLotus effectelectron beam lithographydroplet controlthesishttp://ntur.lib.ntu.edu.tw/bitstream/246246/51015/1/ntu-96-R94525018-1.pdf