以磁性濺鍍氧化鋅量子點嵌入於二氧化矽之尺寸效應探討

Abstract

由於氧化鋅材料的寬能隙與激子結合能高達60meV等半導體特性，近年來氧化鋅量子點的各種製備方法已經日趨成熟，也廣泛地應用在多種熱門的光電元件上，例如LED和雷射。到目前為止，絕大部分使用物理性沉積技術的製備方法，皆需要經過退火的步驟形成氧化鋅量子點。在本論文中，我們使用磁性濺鍍技術在室溫下成長氧化鋅量子點於非晶二氧化矽。實驗結果顯示，在不退火的情況下，我們成功地使用磁性濺鍍技術製備可激發出能量為3.38eV的近紫外光氧化鋅量子點。 含氧化鋅量子點之二氧化矽奈米複合薄膜(ZnO QDs-SiO2 Nanocomposite film)與氧化鋅和二氧化矽之多層膜 (ZnO-SiO2 Multilayer)結構，是本次實驗中兩種主要的製備氧化鋅量子點的方法。將透過穿透式電子顯微技術(TEM)和X-Ray繞射(XRD)探究其結晶特性，量測穿透率與發光頻譜分析其光學特性。因為尺寸相關的量子點侷限效應，從發光頻譜上，可以清楚地觀察到因氧化鋅材料尺寸變小而使能量從3.26eV藍移到3.38eV的現象。最後，將實驗結果與理論模擬做對照，並探討其間的差異。

Recently, ZnO quantum dots are fabrication in variety methods and mainly applied to the popular optoelectrics devices due to its wide direct bandgap and large binding energy. In this thesis, we fabricated the ZnO quantum dot in SiO2 surroundings using magnetron sputtering at room-temperature. Thermal annealing is almostly necessary up till now to prepare ZnO quantum dots showing UV emission. However, this work demonstrates that ZnO quantum dots showing the desired characteristics in absorption and photon emission at 3.38eV in UV can be prepared by sputtering without annealing. Two of structures to fabricate ZnO quantum dots are investigated as followed, which are ZnO QDs-SiO2 nanocomposite films and ZnO-SiO2 multilayers. Transmission electron microscopy (TEM) and X-ray diffraction are used to characterize the crystallinity of ZnO QDs. The optical properties are identified via transmittance and photoluminescence measurements. The blue-shift of ultraviolet emission (3.19eV-3.38eV) and absorption (3.26eV-3.39eV) of the dots are observed, compared to the bulk ZnO material and in different size. It is attributed to the size-dependent quantum confinement effect. Finally, we discuss the difference between experimental data and theoretical simulation in detail.