六角晶格排列之銀奈米結構的表面電漿共振研究

本論文主要在探討由奈米球微影技術(Nano-Sphere Lithography, NSL)所製作的非連續週期金屬(銀)島狀結構的光學特性，利用嚴格耦合波分析(Rigorous Coupled Wave Analysis, RCWA)的方法，計算銀週期島狀陣列在Kretschmann全反射架構下的反射率光譜曲線，並藉由入射光與週期結構倒晶格向量耦合的理論分析，討論全反射光譜中所觀察到的反射率異常變化之來源機制。過程中，我們先計算了具有奈米週期空氣孔洞陣列的連續銀金屬薄膜之全反射光譜作為比較，初步判斷非連續銀島狀結構的異常反射率，主要是源自於入射光與週期結構之倒晶格向量的耦合所造成的現象。接著再計算不同入射光波長條件下的全反射光譜變化，找出發生異常反射率之入射光角度隨波長的變化趨勢，並與經由倒晶格向量的耦合而可能產生之表面電漿共振以及Wood異常散射之入射角度與波長條件進行比較，成功地找出在全反射光譜中所觀察到的異常反射率變化，主要是由銀與空氣界面以及銀與稜鏡界面間的表面電漿共振(Surface Plasmon Resonances, SPRs)或是Wood異常散射現象(Wood’s Anomalies)所造成。

關鍵字

內全反射光譜；二維週期光柵；表面電漿共振；倒晶格向量

並列摘要

In this thesis, the optical properties of the periodic silver nano-island arrays (PSNIAs) fabricated by nanosphere lithography (NSL) method are investigated numerically. We use the method of rigorous coupled wave analysis (RCWA) to calculate the attenuated total internal reflection (ATR) spectra of different PSNIAs. In the ATR spectra, we observed some peculiar reflection fine dips. To find out the physical mechanisms that results in these peculiar reflection fine dips, we firstly calculated the ATR spectra of silver thin films with periodic nano hole arrays (PNHAs) using RCWA, which have been much detailed investigated. From the comparison of the ATR results between PSNIAs and PNHAs, we believe that the peculiar ATR fine dips in the PSNIA should come from the coupling between incident light and the reciprocal grating-vectors (G-vectors) of the PSNIA. After further investigating the ATR spectra of the PSNIAs with different incident angles and wavelengths, these peculiar ATR fine dips were successfully correlated with the G-vector assisted surface plasmon resonances or Wood’s anomalies that occur at the silver/air and silver/prism interfaces.

並列關鍵字

Two dimensional gratings ； Surface plasmons ； Refelction spectra ； Reciprocal grating-vector coupling

參考文獻

[1] S. Szunerits, X. Castel, and R. Boukherroub, “Surface Plasmon Resonance Investigation of Silver and Gold Films Coated with Thin Indium Tin Oxide Layers: Influence on Stability and Sensitivity,” J. Phys. Chem. C 112, 15813–15817 (2008).

[2] R. Morarescu, H. Shen, R. A. L. Vallée, B. Maes, B. Kolarica, and P. Damman, “Exploiting the localized surface plasmon modes in gold triangular nanoparticles for sensing applications,” J. Mater. Chem. 22, 11537-11542 (2012).

[3] C. J. Hsu, K. P. Chiu, J. T. Lue, and K. Y. Lo, “Enhancement of reflective second harmonic generation using periodically arrayed silver-island films,” Appl. Phys. Lett. 98, 261107 (2011).

[4] C. H. Lu, C.C. Lan, Y.L. Li, and C.P. Liu, “Enhancement of green emission from InGaN/GaN multiple quantum wells via coupling to surface plasmons in a two-dimensional silver array,” Adv. Funct. Mater. 21, 4719-4723 (2011).

[5] R. W. Wood, “On a remarkable case of uneven distribution of light in a diffraction grating spectrum,” Phil. Magm. 4, 396-402 (1902).

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六角晶格排列之銀奈米結構的表面電漿共振研究

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