光子晶體為不同折射率介質以週期性排列分布而成的結構，其獨特的光子能隙特性已被廣泛地研究及應用在雷射、波導、太陽能電池…等等光學元件中。大部分的人工光子晶體是藉由光蝕刻的方式製作，對於光子能隙在可見光波段的三維光子晶體，在結構上的精密度與製程上的精細度有更高要求。藍相液晶存在於膽固醇液晶態與各向同性態間，而其結構為自組裝的三維光子晶體，可藉由旋性摻雜物或外加場控制其週期。藍相晶體的成長一般是將整個藍相液晶盒從各向同性態降溫至藍相液晶態，以等向成長的方式形成多晶，由於不同的降溫速率藍相晶體的直徑一般介於3–200 μm。因此，藍相多晶具有晶格軸向不一、晶粒小、晶界多，使其在應用上有諸多的限制。
有別於以往的成長方式，本研究是利用二個不同溫度的平台，分別設定在各向同性態溫度與藍相液晶態溫度。將藍相液晶盒從各向同性態的溫控平台，慢慢移動到藍相液晶態的溫控平台，讓晶體可以沿著移動方向慢慢成長出藍相晶體。利用這樣的方式，開發出大幅超越現有的藍相光子晶體單晶尺寸，甚至達到毫米以上的單晶大小。在實驗中，我們分別去討論了不同的移動長晶參數，有藍相液晶材料、溫度、移動速率、外加場的配向膜與電場，透過顯微鏡去觀察不同移動長晶參數對藍相晶體的晶形、晶格繞射條紋及光頻譜的變化。除了觀察藍相液晶的物理光學特性之外，我們也去探討了藍相液晶的光電特性，透過結晶出不同大小的藍相晶體，量測其光電遲滯特性的變化。
在本研究中，在適當的條件下進行移動長晶，我們得到毫米等級大小的大顆藍相單晶，對於藍相液晶基本特性探討與其光子晶體能隙在調控元件上的開發，開啟了一條新的康莊大道。

Photonic crystals are optical materials with periodically distributed refractive indices. Their photonic bandgap effect on the flow of photons makes them appear colored like the wings of a Morpho butterfly. They have potential for use in nano lasers, photovoltaics, nonlinear optics, and other applications. Most of artificial photonic crystals are made by photolithography. For three-dimensional photonic crystals having their photonic bandgaps in the visible spectrum, the required precision and accuracy of fabrication are extremely high. Blue phases (BP) are a class of particular liquid crystal (LC) phases located between the isotropic and cholesteric phase. Such materials in their blue phases (BPI and BPII) organize spontaneously into three-dimensional cubic nanostructures. By controlling the chirality of the material or applying external fields, the color (bandgap) of a BPLC can be modulated. The conventional way of growing BP crystals is to cool the sample slowly and homogeneously from the isotropic state to the blue phase, resulting in polycrystalline texture. The diameter of each single crystal can range from 3 to 200 μm depending on the cooling rate. BP polycrystals often lack uniform lattice directions, sufficient number of periods, and grain boundaries cause optical scattering, therefore hindering their applications.
In this study, we created spatial temperature gradient by using two temperature-controlled stages. One stage was set at a temperature above the clearing point (the ISO stage) and the other at a temperature in the BP range (the BP stage). The BP crystal growth was conducted by moving the sample from the ISO stage to the BP stage. The single BP crystals thus grew along the moving direction. The resulting single crystals are considerably larger than those grown by the conventional approach. In this thesis, we discussed the parameters that affect the grain size, such as material, temperatures of stages, moving rate, and the addition of external fields. In the experiments, we examined the grain size and other properties of the BP crystals by means of microscopic images, Kössel diagrams, spectra and voltage-transmittance diagrams.
By adopting the proposed strategy for crystal growth, we have achieved millimeter-sized BP single crystals, enabling a wider range of applications and more in-depth fundamental research.

論文審定書 i
致謝 ii
中文摘要 iv
Abstract v
目錄 vii
圖錄 x
表錄 xiv
第一章 緒論 1
1-1藍相光子晶體在應用的必要性 1
1-2藍相液晶的晶粒大小對光電特性的影響 2
1-3成長大顆藍相單晶的必要性 3
第二章 液晶簡介 4
2-1液晶的起源 4
2-2液晶的物理特性 4
2-2.1溫度對秩序參數(S)的影響 5
2-2.2折射率異向性(n) 9
2-2.3介電係數異向性() 11
2-2.4彈性連續體理論 12
2-3液晶的分類 14
2-3.1向列相 15
2-3.2膽固醇相 15
第三章 藍相液晶簡介 18
3-1藍相的起源 18
3-2藍相的結構 19
3-3聚合物穩固型藍相(Polymer-Stabilized Blue Phase) 21
3-4藍相的光電特性 22
3-4.1布拉格反射 (Bragg reflection) 22
3-4.2電場引致的克爾效應 (Kerr effect) 23
3-5藍相的判別方式 24
3-5.1偏光顯微鏡 (Polarizing Optical Microscopy) 25
3-5.2晶格繞射圖像 (Kossel Diagram) 25
3-5.3反射光譜(Reflection Spectra) 27
第四章 實驗架設原理簡介 28
4-1藍相液晶材料的準備 28
4-1.1藍相液晶材料介紹 28
4-1.2藍相液晶的配置 30
4-1.3元件製作過程 31
4-1.4邊界力對藍相液晶分子排列的影響 33
4-2移動長晶的起源 34
4-2.1降溫長晶法 34
4-2.2人工長晶法 36
4-2.3移動長晶法 40
4-3量測架設與分析 42
4-3.1在偏光顯微鏡下量測藍相的光學特性 42
4-3.2藍相晶體的光電特性量測與分析 44
第五章 移動長晶結果與討論 46
5-1藍相液晶材料對藍相晶體生長之影響 46
5-1.1藍相液晶對移動長晶的影響 46
5-1.2聚合物穩固型藍相液晶對移動長晶的影響 48
5-2溫控平台溫度對藍相晶體生長的影響 51
5-2.1各向同性態的溫控平台設定 51
5-2.2藍相液晶態的溫控平台溫度設定 51
5-3移動速率對藍相晶體生長之影響 53
5-3.1移動長晶法 54
5-3.2走返長晶法 63
5-3.3斷尾再生法 65
5-4外加場對藍相晶體生長之影響 70
5-4.1配向膜對藍相晶體生長的影響 71
5-4.2電場對藍相晶體生長的影響 75
5-5藍相晶體之光電特性 76
第六章 結論與未來展望 78
參考文獻 80

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