包覆其他金屬的銀奈米顆粒之表面電漿子共振與耦合行為

Abstract

在本論文中，我們於氮化銦鎵量子井結構上製作銀奈米顆粒，並分析被其他金屬包覆之銀奈米顆粒的表面電漿子共振與耦合行為。理論上，兩種金屬的交界面並不會產生表面電漿子共振，但我們發現在鈦或鋁薄膜上製作銀奈米顆粒時，可以觀察到顯著的表面電漿子共振效應，若在銀奈米顆粒上覆蓋鈦或鋁，或者在銀奈米顆粒下方也有鈦薄膜，形成鈦/銀奈米顆粒/鈦或鈦/銀奈米顆粒/鋁的三明治結構時，也有類似的共振現象。我們也展示了當表面電漿子共振波長與量子井的發光波長相近時的耦合效果，內部量子效率的提昇及光致激發螢光衰減時間的減少都證實有顯著的表面電漿子耦合效應。我們推斷在被其他金屬完全或部份包覆的銀奈米顆粒所觀察到的表面電漿子共振現象是因為銀與其他金屬之間形成氧化物薄膜，可能是氧化鋁或氧化鈦在金屬之間形成介電質夾層。我們也進行理論模擬，確認這樣的介電質夾層會導致表面電漿子共振現象，但其共振強度相較於未覆蓋金屬時會略為減弱。

The surface plasmon (SP) resonance behaviors of Ag nanoparticles (NPs) surrounded by other metals and the SP coupling effects with InGaN/GaN quantum wells (QWs) below the metal nanostructures are demonstrated. Theoretically, SP resonance cannot occur at the interface between two different metals. However, in our study, significant SP resonance behaviors can be observed when Ag NPs are formed at the tops of Ti and Al films, covered by Ti and Al films, or sandwiched by Ti and/or Al films. The effects of SP coupling with the QWs, which emit light at the wavelengths close to SP resonance peaks, are also illustrated. The increase of internal quantum efficiency and the decrease of photoluminescence decay time of the QWs confirm the strong SP coupling effects. The SP resonance behaviors at the Ag NPs partly or completely surrounded by other metals are attributed to the formation of an oxidized thin layer between Ag and other metals. In particular, TiOx and AlxOy can be easily formed at the interface for forming a dielectric interlayer. Based on simulation studies, such a dielectric interlayer can result in significant SP resonance although it becomes weaker.