金屬奈米結構散射與吸收特性之數值模擬

Numerical Simulation on Scattering and Absorption Characteristics of Metallic Nanostructures

彭竣楷(Chun-Kai Peng)

指導教授 ： 江衍偉

共同指導教授 ： 楊志忠(Chih-Chung Yang)

國立臺灣大學/電機資訊學院/光電工程學研究所/碩士(2020年)

https://doi.org/10.6342/NTU202003282

摘要

本論文中，我們藉由數值模擬的方法，探討特定形狀的金屬奈米結構之光學散射與吸收特性，尤其是在表面電漿子共振條件下。首先基於準靜態近似的假設，可利用等效媒質模式，將內部複雜的金屬結構模擬成等效的均勻介質結構，以簡化問題而便於計算。
在接下來的章節中，由於物體形狀簡易，因此我們不再使用等效媒質模式，直接就物體的真正結構作數值計算即可。在多孔金屬奈米球的研究中，我們藉由不同的金屬內部孔洞率，控制不同的表面電漿子共振波長。在金屬塗層介質球的研究中，我們發現了完整金屬塗層與部分金屬塗層間共振特性的差異。藉由不同的金屬塗層厚度，可達到控制不同共振波長的效果。而在銀奈米線的研究中，利用單根與多根的銀奈米線的數值計算，與既有的實驗結果相互比較，讓我們更了解其中的物理意義。透過研究不同形狀的金屬奈米結構，能使我們探究其光學特性與物理意義，這將有助於奈米科技的應用。

關鍵字

金屬奈米結構 ； 表面電漿子 ； 數值模擬

並列摘要

In this thesis, the optical scattering and absorption characteristics of specific metallic nanostructures are numerically simulated, especially under the condition of surface plasmon resonance. First, based on the quasi-static approximation, an effective medium model is proposed to simulate a metallic nanostructure with a complex interior as an effective homogeneous dielectric nanostructure. This simplified structure can then be easily treated numerically.
Since mainly the nanostructures of simple shape are focused on, we perform numerical calculation directly for the true nanostructures without using the effective medium model. In studying porous metal nanospheres, it is found that the surface plasmon resonance wavelength can be controlled by varying the porosity. For metal-coated dielectric nanospheres, we find the difference of resonance wavelengths between a fully coated nanosphere and a partially coated one. Therefore, with a thin metal coating layer of proper thickness on a dielectric nanosphere, the surface plasmon resonance wavelength can be tuned. We also investigate single or multiple silver nanowires, either suspended in the air or laid on a GaN substrate. Numerical results are compared with the existing experimental data to understand the physical mechanism. The simulation results in this study can help us understand the optical properties of some metallic nanostructures, which will be helpful for applications of nanotechnology.

並列關鍵字

metallic nanostructure ； surface plasmon ； numerical simulation

參考文獻

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