臺灣博碩士論文加值系統

在過去的十數年中，蓮葉表面著名的超疏水效應，亦即其接觸角大於140 的現象受到廣泛的研究。本論文提出了一項結合次波長結構與微米等級結構製作複合尺度表面的構想。這類結構與蓮葉表面的結構頗為相似，然而其分佈係以規則狀排列而非如同蓮葉表面之不規則排列。就理論上而言，這種結構預期將具有結合抗反射與自我清潔的效應。

複合尺度光柵的光學特性，在本論文中利用嚴格耦合波分析加以模擬。在模擬的過程中利用有效介質理論將次波長結構進行等效簡化。接觸角則利用Wenzel與Cassie提出的公式分別加以計算。

論文中利用電子束微影製程製作次波長結構，微米等級結構則利用微影製程進行。電感耦合電漿蝕刻在前面這兩道製程完成時分別進行圖形轉移將結構製作在矽晶圓表面。由模擬與實驗量測，證明在微米等級結構上製作次波長結構確實具有抗反射之效果。然而，由於在幾何形狀的結構表面具有較高的遲滯現象，水滴在製作的試片上並無法順利移動，此一成果說明複合尺度結構的自潔效應將需要進一步的探討與實驗改進方有可能克盡全功。

Lotus leaf with super-hydrophobic effect, i.e., the contact angle larger than 140 , was well known and had been studied extensively in the last decade. This thesis proposed a multi-scale grating that is composed by sub-wavelength and micron-scaled surface structures. Such type of structure is quite similar to that of the lotus leaf except that the arrangement in this surface is regular and not as random as that of the lotus leaves. Anti-reflection effect combined with self-cleaning effect is theoretically predicted to be a fundamental characteristics of such surface structure.

The optical behavior of the multi-scaled gratings is simulated by rigorous coupled wave analysis (RCWA). For simulation, an equivalent model derived from the effective medium theory was introduced to simplify the calculations for sub-wavelength gratings. Contact angle estimation was achieved by using Wenzel’s formula and Cassie’s formula.

Electron bean lithography was used to fabricate the sub-wavelength structure. Optical lithography was adopted to obtain micron-scaled surface structures. Patterns were transferred to silicon substrate by inductive coupled plasma (ICP) etching technique once the mask was done by the previous two methods. Comparing the theoretical simulation and experimental verification, it is verified that the anti-reflection effect exists when the sub-wavelength grating is fabricated on the micron-scaled grating. However, the water droplet sliding was hinder by the hysteresis induced by the geometric specimens, which prevents the droplet from sliding freely. It is thus suggested that more investigations on the self-cleaning effect induced by the multi-scale grating must be done in order to further advance the knowledge in this ever more important field.

謝 誌 i
摘 要 iii
Abstract iv
Content vi
List of Figures viii
List of Tables xii
Chapter 1 Introduction 1
1.1 Preface 1
1.2 Review of existed technologies 4
1.2.1 Anti-reflective (AR) effect 4
1.2.2 Self-cleaning effect 11
1.2.3 Super-hydrophobic surface combined with AR effect 19
1.2.4 Droplet control technology 22
1.3 Thesis organization 23
Chapter 2 Theory 25
2.1 Fraunhofer diffraction 25
2.1.1 Diffraction by single slit and multi-slit 26
2.1.2 The diffraction grating 30
2.2 AR sub-wavelength gratings 32
2.2.1 Optical approaches to different scales 32
2.2.2 Effective medium theory (EMT) 34
2.2.3 Gratings with Anti-reflective behaviors 41
2.3 Super-hydrophobic surfaces 52
2.3.1 Contact angle on material surface 52
2.3.2 Hysteresis 58
2.3.3 Enhanced self-cleaning effect for multi-scaled structure 62
Chapter 3 Simulation and Calculation 63
3.1 Optical behavior simulation applying RCWA 63
3.1.1 Simulation of micron-scaled gratings 63
3.1.2 Simulation of sub-wavelength gratings and their effective models 71
3.1.3 Simulation of multi-scaled gratings 80
3.2 Contact angle calculations 84
3.2.1 Contact angle calculations for micron-scaled structures 84
3.2.2 Contact angle calculations for triangular structures 88
Chapter 4 Experiments 91
4.1 Fabrication of multi-scaled gratings 91
4.1.1 Fabrication procedure 91
4.1.2 Sub-wavelength gratings fabrication 94
4.1.3 Micron-scaled gratings fabrication 102
4.1.4 Teflon coating 106
4.2 Measurement of specimens properties 109
4.2.1 Measurement of optical behaviors 109
4.2.2 Measurement of contact angles on structured surface 114
Chapter 5 Discussions and Future Works 123
5.1 Discussions 123
5.1.1 Optimization of diffraction gratings 123
5.1.2 Improvement of multi-scaled grating fabrication 124
5.1.3 Hydrophobic contact angle on hydrophilic structures? 125
5.2 Future work 128
Chapter 6 Conclustions 135
Reference 138
Appendix I. Effective thin film calculation applying EMT 146
Appendix II. Detailed data for specimens 148

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