銦化砷銦化鎵與掺鈷氧化鋅低維度奈米材料的光學特性研究

Abstract

本論文主要利用光學技術的方法，進行低維度奈米材料的發光特性研究，主要可分成兩部份： 第一部份為零維量子結構的螢光光學特性研究。我利用了量子點與量子環來進行螢光激發光譜與活化能的比較。由螢光激發光譜可得知量子點與量子環有不同的行為，我們歸咎於它們的分立能階座落於不同位置，因此載子會有兩種不同鬆弛機制。由變溫螢光所得到量子點與量子環的活化能，雖然量子環活化能較小，但因為內部有Dark Stated存在，可提供載子另一條路徑，因此高溫時放光效率較佳。 第二部份為利用時間相關單光子計數器的技術，並在不同溫度下進行掺鈷氧化鋅奈米線的量測。實驗結果得知，由氧化鋅缺陷與由鈷造成的d-d躍遷在改變溫度時，載子生命期會有不同結果，我們利用能階模型來解釋它們的差異。

In this thesis, we used optical techniques to investigate semiconductor low-dimensional structures. The thesis was composed of two parts: In the first part, we investigated optical properties of zero-dimensional nanostructure. We compared results of quantum dots (QDs) with quantum rings (QRs) by measuring photoluminescence excitation (PLE) and activation energy (Ea).In the PLE spectrum, we observed different behavior between dots and rings. The two different results were ascribed to the position of discrete state in the QDs and QRs, which leads to two distinct relaxation mechanisms for the carriers in the QDs and QRs. We could obtain the Ea in the QDs and QRs were retrieved from the temperature dependent PL spectra. Although the Ea of the QRs is smaller, however, the dark state in the QRs provide an escaping channel for the photoexcited carriers. Therefore, the luminescence efficiency is better in the QRs at high temperature. In the second part, we used time correlated single photon counting technique to investigate the PL lifetime in cobalt doped zinc oxide (ZnO) at various temperatures. We observed the different behaviors of carrier relaxation between ZnO defect and d-d transition .An energy level model was proposed to explain our experimental results.