一維結構硫化鋅奈米線生長機制及其衍生異質結構光學特性之探討

在本篇研究中，藉由本實驗室過去研究的合成方法，利用單源先驅物進行溶液-固體-固體法（SSS method）及磊晶生長（epitaxial growth），調控不同之合成溫度（120-200 °C）及合成時間，合成出筆直的一維硫化鋅半導體奈米線。並透過穿透式電子顯微鏡（TEM）及高解析穿透式電子顯微鏡（HRTEM）觀測奈米線的形貌、直徑分布及晶相組成，利用X光繞射技術（XRD）及X光近緣吸收光譜（XANES）與延伸X光吸收精細結構（EXAFS）來分析奈米線的晶粒變化與原子在空間位置上的改變，綜合各項技術來探討奈米線在不同溫度下，不同反應時間所對應之反應機制，並提出奈米線生長機制之模型，進而調控奈米線生長之形貌。對硫化鋅奈米線進行進一步的合成，可合成出硫化鋅-硫化鎘異質半導體奈米線，藉由引入較低能障（band gap）的硫化鎘，生成type-II半導體的奈米結構，使用穿透式電子顯微鏡及元素分布分析（EDS mapping）技術觀測其形貌與元素組成，並藉由紫外可見光吸收光譜（UV-Vis absorption）、光致螢光光譜（PL）ヽ螢光激光光譜（PLE）來分析異質奈米線的電子結構，最後與單光子計數系統（TCSPC）所得到的生命週期（lifetime）數據進行比對，進而解釋異質結構中電荷分離之分離路徑。

關鍵字

單源先驅物；溶液-固體-固體法；磊晶生長；一維結構；硫化鋅奈米線；生長機制；異質結構； type-II半導體；電荷分離

並列摘要

In our recent studies, when single-source precursors (SSP) dissolve in oleylamine, 1D semiconducting nanowires which are synthesized at different temperature (120-200 °C) and reaction time can cause major variance in both wire morphologies and diameter distributions via simple thermal decomposition, solution-solid-solid method (SSS) and epitaxial growth. We also observe TEM and HRTEM images to recognize wire morphologies and composition of phases (wurtzite and zinc blende). X-ray absorption (XANES and EXAFS) and X-ray diffraction techniques are employed directly monitor the structural and morphological evolutions at each step of wire growth. Based on the result of each technique at different synthetic temperature and the evolutions of wire shapes and diameter distributions, we propose the ZnS nanowires growth mechanism. Then Ag2S, which is attached with ZnS nanowires, catalyzes the growth of CdS nanowires and further synthesizes ZnxCd1-xS type-II heterojuction nanowires. The heterostructures and compositions are characterized in TEM/STEM techniques with spatial EDS mapping. The band structures are revealed by multiple fluorescence profiles in NIR, visible and UV regimes, resulting in lifetimes for different recombination pathways. Epifluorescence from single heterostructure nanowires further confirms the ensemble emission profiles which suggest charge separations in the 1D heterostructures.

並列關鍵字

single-source precursors ； 1D semiconducting nanowires ； solution-solid-solid method ； epitaxial growth ； growth mechanism ； type-II heterojuction ； charge separations