電漿改質自組裝分子膜於微影化學圖形與製作奈米粒子三維電漿子晶體之應用

Plasma Modification of Self-Assembled Monolayers for Chemical Patterning and Fabrication of Large-Area 3D Plasmonic Supercrystals

林孟賢(Meng-Hsien Lin)

指導教授 ： 果尚志

國立清華大學/工學院/奈米工程與微系統研究所/博士(2011年)

https://doi.org/10.6843/NTHU.2011.00030

摘要

為了將元件體積微型化或執行更為精密的功能，奈米科技已然成為當前主流的發展技術之一，而奈米圖案成像技術與奈米結構製造技術亦將隨著各種功能元件的製作或整合需求而更加快速發展，以應用於奈米電子、奈米光電元件、奈米機電、分子電子元件、資料儲存、感測器、生物晶片及超穎材料等重要領域。因此本研究提供了一種在表面製造圖形化官能基的有效方法，用以提供有別傳統光學微影且不侷限於光學繞射極限的技術。由此技術我們更延伸出一種用於製作三維金、銀奈米粒子超晶格薄膜的方法，由於奈米粒子具有獨特的表面電漿子特質，因此奈米粒子超晶格薄膜結構的製造方法在未來設計電漿子超穎材料領域將預期能發揮重要關鍵作用。
在研究執行中主要是利用高活性電漿與局部區域自組裝單分子膜(SAMs)接觸產生化學官能基轉變，用以達成在表面製造出圖形化官能基。而使電漿與局部SAMs接觸的調控方式則是利用聚甲氧基矽氧烷(PDMS)製造接觸式的孔洞遮罩或擁有流道溝槽的”圖章”，而由PDMS所製造出的表面化學圖形化尺度可橫跨公分至奈米，而其最小解析線寬將可達50奈米。我們利用一系列廣泛的分析技術來觀測研究表面局部的官能基化學轉變特性，其中包括水接觸角量測，同步輻射X-ray光電子能譜(XPS)，同步輻射掃描式光電子能譜(SPEM)，熱場發掃描式電子顯微鏡(FE-SEM)及掃描探針表面電位影像(SKPM)。尤其XPS與SPEM的影像能譜，更可有效的分析出局部圖形化區域的官能基相異性及電漿改質官能基轉換的機制。
接著利用電漿改質分子膜的技術，我們延伸出一種簡單且有效的方法用於製作大面積(>平方公分)的三維金、銀奈米粒子超晶格薄膜，在此法中，使用被硫醇包覆的金銀奈米膠體粒子，藉由電漿改質處理使其具有雙面神(Janus)奈米粒子的特性(一面為溶液相斥性一面為溶液相親性)，可達到逐層操控堆疊奈米粒子的目的。我們更進一步的驗證此薄膜在同層粒子(橫向平面)及層與層之間(垂直縱向)都具有三維電漿子晶體的強近場耦合現象。與傳統利用聚合相異電介質交互堆疊的逐層堆疊方式相比，這個方法能夠明顯的藉由光譜觀察到層數與縱向(Z向)多重耦合模態的關係。我們發覺在反射光譜中被吸收波段波谷(相關於縱向耦合模態)與層數間的關係能夠說明在縱向方向具有一個電漿子法布立–培若奈米共振腔(plasmonic Fabry-Pérot nanocavity)。而此電漿子晶體結構可以在特定調控的波段產生電漿子駐波，而且可調控的電漿子頻率具有橫跨可見光至近紅外光範圍的能力。

關鍵字

負折射率 ； 超穎材料 ； 奈米粒子 ； 表面電漿 ； 表面改質

並列摘要

Nanotechnology has been developed as a reliable technology for producing minimal components to perform more precise functions. In particular, the availability of nanolithography and nanostructure fabricating processes is important in the fields of photonics, electronics, biotechnology, and metamaterial. In our research, we present a generic and efficient chemical patterning method, compared with conventional photolithography this approach is without diffraction limit. Base on this approach, we expand a method for synthesizing three-dimensional (3D) gold and silver nanoparticle supercrystal films. Since nanoparticles have unique properties of surface plasmon, this technology will offer a pathway to designer plasmonic metamaterials.
We fabricate chemical pattern based on local plasma-induced conversion of surface functional groups on self-assembled monolayers. Here, spatially controlled plasma exposure is realized by elastomeric poly(dimethylsiloxane) (PDMS) contact masks or channel stamps with feature sizes ranging from nanometer, micrometer, to centimeter, and an achievable resolution is down to the 50 nm range. This chemical conversion method has been comprehensively characterized by a set of techniques, including contact angle measurements, X-ray photoelectron spectroscopy (XPS), scanning photoelectron microscopy (SPEM), scanning electron microscopy (SEM), and scanning Kelvin probe microscopy (SKPM). In particular, XPS and SPEM can be used to distinguish regions of different surface functionalities and elucidate the mechanism of plasma-induced chemical conversion.
Based on plasma-induced conversion, we expand a simple and efficient method for synthesizing large-area (>cm2), three-dimensional (3D) gold and silver nanoparticle supercrystal films. In this approach, Janus nanoparticle (top face solvent-phobic and bottom face solvent-philic) films with an arbitrary number of close-packed nanoparticle monolayers can be formed by using layer-by-layer (LbL) assembly from suspensions of thiolate-passivated gold or silver colloids. Furthermore, we demonstrate that these films can act as true 3D plasmonic crystals with strong transverse (intralayer) and longitudinal (interlayer) near-field coupling. In contrast to conventional polyelectrolyte-mediated LbL assembly processes, this approach allows multiple longitudinal coupling modes with a conspicuous spectral dependence on the layer number. We have found a universal scaling relation between the spectral position of the reflectance dips related to the longitudinal modes and the layer number. This relation can be understood by the presence of a plasmonic Fabry-Pérot nanocavity along the longitudinal direction, allowing the formation of standing plasmon waves under plasmon resonance conditions. The realization of 3D plasmonic coupling enables broadband tuning of collective plasmon response in a wide spectral range (visible and near-infrared) and a key pathway to designer plasmonic metamaterials.

並列關鍵字

NEGATIVE REFRACTIVE-INDEX ； JANUS PARTICLES ； METAMATERIALS ； NANOPARTICLES ； PLASMON ； SURFACE MODIFICATION

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