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標題: | 製作奈米結構使分子配向於奈米光電元件之應用 Nanostructure Fabrication for Molecular Alignment in Application of Opto-Electric Nanodevices |
作者: | Tzu-Chieh Lin 林紫婕 |
指導教授: | 趙治宇(Chih-Yu Chao) |
關鍵字: | 液晶配向,奈米結構,軟微影, liquid crystal alignment,nanostructure,soft lithography, |
出版年 : | 2010 |
學位: | 博士 |
摘要: | 舉凡生醫或光電等領域,分子配向一直以來均有其重要之應用性。其中製作奈米溝槽是用以導引分子使其有序排列方法之一。在本篇論文裡,我們探討了數種製作奈米結構的軟微影術,並將其應用在奈米光電元件。根據Berreman理論,液晶分子為使表面自由能達最小值,而沿表面溝槽方向排列。控制液晶分子之排向在液晶顯示器中扮演了舉足輕重的角色,它決定了液晶層能否成功的控制光線出入,進而成為一有效之光閥。
首先,我們使用了導電原子力顯微術 (conductive atomic force microscopy nanolithography),外加電場於p型矽基板上,氧化成長無機之二氧化矽奈米溝槽,以製備反射式之液晶晶胞。原子力顯微術提供了精細之畫素與高解析度,以及能更準確的控制液晶分子的次序性。相對於一般傳統摩擦配向膜的方式,不僅免去了高溫製程,無機的配向層亦不會因摩擦產生碎屑及靜電,且可承受製程時的紫外線傷害與操作環境之高溫。適用於小尺寸面板、投影機及可攜電子式產品的應用。 本論文於第四章介紹利用創新之軟微影技術(soft lithography) - 破裂觸發自組裝溝槽(crack induced self-assembled grooves) - 來使液晶分子配向。此方法利用高分子層內的行進波於上下基板之間來回震盪,形成正弦波的溝槽。由實驗歸納得出,溝槽的週期與高分子層的膜厚相關,約成四倍的關係,亦與理論符合。我們於本論文中做出最小約70 nm線寬的溝槽。利用此方法我們可用膜厚調控溝槽週期,進而控制液晶之定錨能以及對比度,效果接近以傳統絨布摩擦PI (polyimide)配向膜。此軟微影術提供一快速簡易且不需外加任何模子(mold)的方法,我們於本論文中介紹了技術細節以及理論運算。 最後,我們介紹了另一種特殊的軟微影方法 - 熱致拉引法(thermal drawing) - 以製作自組裝溝槽,我們使用了具grating圖案的矽基板當作上模,加熱下基板之高分子,根據ICE Model的靜電理論,利用上模與高分子之間的靜電力拉引熔融之高分子,使之形成與上模同樣pattern的高分子溝槽。此方法為AFM-assisted electrostatic nanolithography (AFMEN) 之更進階,其可免去AFM掃描,以提升面積與效率,且不需外加電場熔融高分子。用此方法製作溝槽來使液晶分子配向,可避免摩擦配向造成之缺陷,不僅可製成反射式液晶晶胞,也可應用在穿透式的液晶晶胞。 本篇論文介紹利用數種新穎的軟微影技術,以製作奈米級溝槽使液晶分子配向,這些方法不僅能應用在液晶顯示器,還可用於生物晶片、微流通道、積體電路、太陽能電池等生醫光電產品,於現在及未來均具有相當前瞻之應用性。 Molecule alignment has many significant applications in biotechnology, molecular electronics, optoelectronic devices and liquid crystal (LC) displays manufacturing. Fabrication of nanogrooves is one of the approaches for ordering molecules. In this dissertation, we investigate several nanolithography generating nanostructures and apply them in opto-electric devices for liquid crystal alignment. At first, in Chapter 3, conductive atomic force microscopy (CAFM) nanolithography was used to modify a silicon surface. This approach generating the silicon oxide grating by CAFM gives a good control of liquid crystal (LC) alignment in the micron or submicron region. It establishes a pixel with a smaller size to achieve high-resolution images. Compared with the conventional cloth rubbing and AFM scratching techniques, CAFM nanolithography prevents scratching damage, dust contamination and residual static electricity problems. Furthermore, this inorganic alignment method can also avoid the damage caused by UV light exposure and high-temperature environment. It could be applied to small panels, projectors, liquid crystal on silicon (LCOS), and portable electronics. In Chapter 4, we employed a fast and high-throughput method, fabricating micro- and nano-grooves for the alignment of liquid crystal molecules. Splitting the polymer film sandwiched by two substrates triggers the propagating wave front to induce self-assembled grooves on the polymer surfaces. This crack-induced grooving (CIG) method not only avoids the high-temperature process, dust and ion contaminations caused by traditional rubbing, but also provides a large anchoring energy comparable to that using polyimide rubbing. This CIG method could generate tunable-period grooves without any masks. It also offers an appealing alternative to existing technologies for LC molecules alignment. In Chapter 5, we represented a fascinating soft lithography - thermal drawing lithography (TDL) - to fabricate self-assembled periodic grooves. The prepatterned silicon mold with protruding grating, exists a spacer gap, is placed on a bottom substrate spin-casted with polymer film. According to the image charge-induced electrohydrodynamic-instability (ICE) model, the attractive electrostatic force between upper and bottom substrates would cause heat-induced melting polymer film to rise and form a positive replica grating pattern similar to the upper mold. In our work, we confirm thermal drawing lithography could be achieved without an external electric field and prove the ICE model by experimental results. We have utilized these self-assembled grooves to align liquid crystal molecules for both reflective and transmissive liquid crystal cells. In this dissertation, we introduce several novel soft lithography fabricating nanogrooves for liquid crystal alignment. Not only for liquid crystal displays, these approaches fabricating submicro or nano-structures provide a simple means and have great potential for many other fields, like biochips, microchannels, molecular circuits, solar cells, etc. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/10552 |
全文授權: | 同意授權(全球公開) |
顯示於系所單位: | 物理學系 |
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