金屬性氧化鋁鋅侷域性表面電漿特性與表面增強紅外光譜應用之研究

Abstract

當光照射到金屬奈米粒子並且達到表面電漿共振時，光會被侷限在次波長的區域中，並且在金屬奈米粒子周遭產生強烈的電場，因此，透過這些強烈的電場，金屬奈米粒子可以應用在體折射率感測，化學偵測，以及奈米粒子捕捉等。通常，因為擁有較高的載子濃度，金屬奈米粒子的材料大多為金，銀，等貴金屬。然而這些貴金屬在光學波段下，有嚴重的載子間帶躍遷和帶內躍遷，因而造成額外的能量耗損。此外，高濃度載子也造成貴金屬有高的輻射阻尼而有嚴重的輻射散失。另一方面，透明導電氧化物可以成為低損耗電漿材料，因為透明導電氧化物在紅外波段有較低的間帶躍遷和帶內躍遷。本篇論文，我們利用電子束微影系統在光阻上定義出奈米環正方陣列，再由射頻磁控濺鍍機沉積氧化鋁鋅(aluminum-doped zinc oxide, AZO)薄膜，最後透過舉離步驟製造出AZO奈米環陣列。並且，透過COMSOL軟體模擬及分析AZO奈米環陣列的表面電漿共振之特性。在COMSOL模擬中，介電函數是由AZO薄膜穿透率計算而得。藉由此介電函數，我們得到了模擬的消光光譜和實驗的消光光譜十分吻合，說明了我們的介電函數不只可以用來描述AZO薄膜特性，也適合用來分析AZO奈米環陣列之表面電漿共振的特性。我們也在實驗及模擬中發現，表面電漿共振之共振波長會隨著AZO奈米環陣列幾何結構而改變。最後，我們應用AZO奈米環陣列於表面增強紅外光譜，並且展現了AZO奈米環陣列具有高度的淺力於表面增強紅外光普之應用。

When the light illuminates metallic nanoparticle and is satisfied the conditions of local surface plasmon resonance (LSPR), the light will be confined in subwavelength scale, and the intensive enhancement of localized field around the metallic nanoparticles occurs. Therefore, these metallic nanoparticles can be served as plasmonic devices to achieve manifold applications including bulk refractive index sensing, chemical sensing, and trapping. Usually, the plasmonic devices are made of metals such Au or Ag because their high carrier concentration can intensively interact with light. However, suffering from high interband and intraband transition in optical frequencies, metal plasmonic devices operated in optical frequencies result in large losses. Furthermore, the high carrier concentrations in metals also lead seriously radiative losses. Moreover, the transparent conducting oxides (TCOs) can be suitable candidate for low-loss plasmonic materials in NIR region due to lower interband and intraband transition losses. In this thesis, I fabricated the AZO nanoring arrays by e-beam lithography to pattern the nanoring arrays and radio frequency (RF) magnetron sputtering system to deposit AZO thin film. The simulation of LSPR properties by COMSOL software utilized the dielectric function retrieved from AZO thin film. And I demonstrated highly consistent extinction spectra in simulation and experiment. Moreover, the AZO nanoring arrays have been utilized to achieve surface-enhanced infrared spectroscopy. Therefore, the AZO nanoring arrays perform high potential in chemical sensing.