金屬奈米腔效應對量子點發光與福斯特共振能量轉移行為的影響

Abstract

本篇論文研究中，為了瞭解金屬奈米腔對塞入腔體內量子點與附近量子井發光行為的影響，我們製作了兩種奈米尺度的金屬腔體。首先，在氮化鎵奈米洞之底部與側壁鍍上金或銀就形成金屬奈米洞。另外，在氮化鎵奈米洞中只在侧壁上鍍上金屬就得到金屬奈米管。金屬奈米洞的形成係將金屬直接沉積至氮化鎵奈米洞上。金屬奈米管的形成則是使用二次濺鍍的技術，利用反應性離子蝕刻的三氟甲烷離子轟擊洞底的金屬原子，使其濺鍍到奈米洞側壁。由於銀的二次濺鍍技術不成熟，我們僅使用金來製作金屬奈米管樣品。由時間解析光激螢光光譜的量測結果顯示，在金及銀金屬奈米洞的樣品中，量子點的發光效率都增加。此外，從綠光量子點到紅光量子點之福斯特共振能量轉移的效率也提高，顯示金屬奈米腔的效應。在沒有量子井的金奈米管樣品中，儘管在管內量子點的發光沒有增強太多，但是從綠光量子點到紅光量子點之福斯特共振能量轉移效率顯著提高。而在具有量子井的金奈米管樣品中，與不帶有金側壁的相應樣品(仍具有量子井)相比，從量子井到量子點之福斯特共振能量轉移效率顯著提高，即使是在金吸收極強的量子井發光波段，仍然可以提高量子井到量子點的福斯特共振能量轉移效率。

Two types of metal nanoscale cavity are fabricated for studying the emission behaviors of the inserted colloidal quantum dots (QDs) and nearby quantum wells (QWs). In a metal nano-hole, the sidewall and bottom of a GaN nano-hole are covered by Ag or Au. In a metal nano-tube, only the sidewall of a GaN nano-hole is covered by metal. A metal nano-hole is formed by simply depositing metal onto a GaN nano-hole. A metal nano-tube is fabricated through the technique of secondary sputtering, in which the metal atoms at the hole bottom are bombarded by CHF3 ions in a reactive ion etching process for sputtering onto the nano-hole sidewall. Because the secondary sputtering of Ag is more difficult, only Au is used for fabricating the metal nano-tube samples. Time-resolved photoluminescence measurements show that the QD emission efficiency in either an Ag or an Au nano-hole sample is increased. Also, the efficiencies of the Förster resonance energy transfer (FRET) from green-emitting QD into red-emitting QD are increased, indicating the effective nanoscale-cavity effect. In an Au nano-tube sample without QW, although the QD emission is not much enhanced, the efficiencies of the FRET from green-emitting QD into red-emitting QD are significantly increased. In an Au nano-tube sample with QW, the efficiency of the FRET from QW into QD is enhanced, when compared with the corresponding sample (with QW) without Au sidewall layer. The FRET from QW into QD can still be enhanced even though Au absorption is strong at the QW emission wavelength.