使用銀奈米線為透明導電體之發光二極體內表面銀奈米顆粒的表面電漿子耦合行為

Abstract

在本論文研究中，我們先將銀納米線覆蓋在氮化鎵基板上，隨後製作銀納米顆粒，並與未覆蓋銀奈米線直接製作銀奈米顆粒的樣品進行比較，發現前者的侷域表面電漿子共振波長明顯較短。後者共振波長通常長於500奈米，而前者則落在可以與藍光量子井耦合的範圍內（約450奈米）。我們推測這種行為是由於聚乙烯吡咯烷酮沉積在基板表面所引起的，聚乙烯吡咯烷酮是用於合成銀奈米線的表面活性劑，留存在銀奈米線的表面上。聚乙烯吡咯烷酮可溶解在銀奈米線溶液中，並與銀奈米線一起鋪在氮化鎵表面。聚乙烯吡咯烷酮在銀奈米顆粒與氮化鎵之間形成一個薄間隙，導致銀奈米顆粒的侷域表面電漿子共振波長藍移。量子井的內部量子效率和光致發光衰減時間的測量顯示，這種藍移行為可以提高量子井在450奈米處與表面銀奈米顆粒的表面電漿子耦合效果，從而提高量子井的發光效率。這種現象可以應用於使用銀納米線作為透明導電體之藍光二極體。

With Ag nanowires (NWs) overlaid onto a GaN template, the localized surface plasmon (LSP) resonance wavelength of subsequently deposited Ag nanoparticles (NPs) becomes significantly shorter, when compared with that in the case without Ag NW overlay. The latter is generally longer than 500 nm while the former falls into the blue range, around 450 nm. It is speculated that this behavior is caused by the settlement of polyvinylpyrrolidone (PVP), which is the surfactant used for synthesizing Ag NW and remains on the surface of an Ag NW. PVP is dissolved in the Ag NW solution and is applied to GaN surface together with Ag NWs. The PVP layer forms a narrow gap between Ag NPs and GaN and leads to the blue shift of the LSP resonance of Ag NPs. Measurements of internal quantum efficiency and photoluminescence decay time in a quantum-well (QW) structure show that this blue-shift behavior can further enhance the emission efficiency of a QW at 450 nm. This phenomenon is applied to the fabrication of a blue light-emitting diode using Ag NWs as transparent conductor.