臺灣博碩士論文加值系統

本論文利用光阻劑及電子束微影技術(Electron beam lithography technique)在二氧化鈦薄膜上，蒸鍍不同角度頂錐角的奈米銀領結形與扯鈴形結構。此結構會於金屬Ag/TiO2介面及空氣/TiO2介面，產生局部表面電漿共振及局部電場增強效應，製備出高效能光吸收的二氧化鈦光觸媒元件。結果顯示，領結形與扯鈴形的銀奈米結構，不僅局部表面電漿共振增強，且隨著頂錐角的角度減小，拉曼光譜之強度越顯著。基於頂錐角的尖端處，具有最大電流密度，故表面電漿共振電場最強位置，侷限於領結形的尖端間隙處或侷限於扯鈴形的腰寬。隨著頂錐角的角度增大，其棱邊長度增長達到表面電漿極化子(SPP)共振腔條件時，產生干涉駐波，是共振波長紅移的原因。反之，近紫外光區的短波長有藍移現象，推測歸咎於短波長駐波沿著領結形軸與扯鈴形軸駐留，導致等效折射率效減小。奈米銀領結形與扯鈴形結構元件置於甲基藍溶液，呈現頂錐角的角度越小的奈米結構，其降解速率越快，證實增強的表面電漿效應，強力助於光的吸收，及增多自由基的數量，促進二氧化鈦光催化之功效提升。

Photoresist and electron beam lithography technique were used to fabricate the evaporated nano silver bowtie and diabolo structure with various tip angles embedded on the surface of titanium dioxide film. The reinforced localized surface plasmon resonance and electric field can be generated at the metallic Ag/TiO2 interface and air/TiO2 interface for making a high light absorbance of titanium dioxide photocatalytic device. The results in both bowtie and diabolo structure show that not the localized surface plasmon resonance (LSPR) enhances, but also the Raman intensity amplifies as the tip angle reduces. On the basis of maximum electric current density at the apex, the strongest surface plasmon resonant confines at the tip gap of bowtie and the waist width of diabolo. As tip angle increase, the resonant wavelength of the standing wave matches the lengthened length of prism edges and red shifts. In the short wavelength region, as tip angle increases, the resonant peak wavelength blueshift presumably attributes to the decrease in the effective index of the local SPP standing wave mainly resided along the both bowtie axis and diabolo axis. The fastest photocatalytic rate by placing bowtie Ag/TiO2 with tip angle 30° in methylene blue solution reveals the best degradation efficiency. Because a great amount of light absorbance can generate many valid radicals by surface plasman resonance enhanced electric field.

Content Caption List
中文摘要…………………………………………………………………………….2
Abstract……………………………………………………….……...……….....….3
Content Caption List……………………..……………….……………...…..….4
Figure Caption List……………..……………….………..………………………….5
Chapter 1 Introduction…………………….……………………………………6
Chapter 2 Experimental procedure…………………………………………..8
2.1 Deposition of TiO2 film on Si wafer by DC sputtering………………………8
2.2 Making bowtie and diabolo patter by using E-beam lithography ….…..……8
2.3 Evaporation of Ag into the pattern………………………………...…………8
2.4 Characterization of photocatalyst film………….………………………....10
2.5 Photocatalytic degradation effect by methylene blue……………..….……10
Chapter 3 Results and Discussions……………………………..……………11
3.1 TiO2 film analysis by X-ray diffraction………………………..……………11
3.2 Bowtie and diabolo analysis by SEM…………….……………………..….12
3.3 SERS effect by Raman spectroscopy…….…………….…………….…….13
3.4 UV-VIS-NIR analysis…….…………….…………….…………….……...16
3.5 Degradation of Methylene Blue……….…………….…………….………18
Conclusions…….………….…………….………...……….…………….………..23
Reference…….…………….…………….…………….…………….…………..24

Figure Caption List
Fig 1 Schematic dimension of nano Ag bowtie (a~c) and diabolo (d~f) with a tip angle at 30°, 60° and 90° respectively……………………………………………………9
Fig 2 The cross-section schematic dimension of nano Ag bowtie(a) and diabolo(b)..10
Fig 3 XRD diffraction of various bowtie Ag/TiO2 and diabolo Ag/TiO2 photocatalyst. ……………………………………………………………………….11
Fig 4 SEM morphology of nano bowtie Ag/TiO2 (a,b,c) and nano diabolo Ag/TiO2 (d,e,f) at various tip angles…………………………………………………………12
Fig 5 Raman spectra of (a) nano bowtie Ag/TiO2 and (b)nano diabolo Ag/TiO2 with various angles. The stars represent the vibration modes of R6G…………………….14
Fig 6 The comparison of enhancement factors obtained in Fig 5.………....15
Table 1 AEF calculation process use table shown………………………....................15
Fig 7 UV-VIS-NIR spectra of (a) nano bowtie Ag/TiO2 (b) nano diabolo Ag/TiO2, both with various tip angles………………………………………………………….17
Fig 8 Photocatalysis of nano bowtie Ag/TiO2 and nano diabolo Ag/TiO2 with various tip angles on the methylene blue (MB) under LED exposure at the composite wavelength…………………………………………………………………………19
Fig 9 Schematic diagram for the SPR enhanced photocatalytic mechanism at (a) the gap cavity of Bowtie and (b) the distribution of SPR in Diabolo…………………..20

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