Fabrication of pure, Metal (Mn, Mg) doped ZnO single nanowire based CO sensors

氧化鋅由於其具有寬能隙(~3.37 eV)的以及室溫下較高的激發活化能(~60 meV)，在室溫下為非常穩定的半導體材料，這些特性使得氧化鋅能作為現今大量製作發展的光電元件的半導體材料。 本論文使用旋轉塗佈法制備氧化鋅晶種層，再將製備好的晶種層樣品利用水溶液法在90 ˚C的環境中生長3個小時，長出大量具單一晶向的氧化鋅奈米線，並透過摻雜元素(錳、鎂…等)。奈米線透過電子顯微鏡觀察其形貌，XRD分析中我們可發現本研究生長的氧化鋅奈米線為單晶結構，其生長方向為(002)方向，同時我們也利用TEM印證同樣的結果。 材料特性檢測部份我們使用拉曼光譜、XPS等儀器對氧化鋅奈米線進行檢測，能觀察到氧化鋅奈米線是以纖鋅礦結構為主、且Zn離子主要是以Zn 2p3/2與Zn 2p1/2為主要的形式存在。 材料檢測部分結束後我們利用聚焦離子束微影法將氧化鋅奈米線製成單根奈米線元件，測量不同的元件電性後再進行室溫下1080ppm的CO氣體感測。結果顯示當使用Sapphire基板生長的氧化鋅奈米線可以量測到CO氣體通入時的電流訊號變化。Zinc oxide (ZnO) is a wide band gap (~3.37 eV) and higher excitation energy (~60 meV) at room temperature (RT) semiconductor. These characteristics allow ZnO been widely used in photo-electric devices. In this study, we use spin-coating to make ZnO seed layer, then fabricate massive single crystalline ZnO nanowires(NWs) by using aqueous solution method at 90 ˚C for 3 hours. We also use some other elements (eg. Mn, Mg …etc) to make dopant at ZnO NWs. The morphology of ZnO NWs has been examined by SEM. The XRD diffraction spectrum demonstrates that the ZNO NWs growing by aqueous solution method are single crystalline along the (002) direction. The TEM also shows the same result. We used Raman spectrum, XPS spectrum …etc instrument to study the material characteristics. We can checked that the ZnO nanowires were mainly wurtzite structure by using Raman spectrum, and the XPS spectrum showed that the orbital of ZnO is mainy 2p3/2 and sp1/2. We can fabricated single ZnO nanowires devices by using FIB, and measuring the IV curve of each devices and measure the CO sensing at room temperature. The sensing results showed that the pure ZnO nanowires on sapphire can clearly measure the current variation when the CO gas was added into the chamber.致謝 i 摘要 ii Abstract iii Content iv Table Caption vi Figure Caption vii Chapter 1 Introduction 1 1.1 Znic oxide properties and structure 1 1.2 Carbon monoxide 2 1.3 Experiment motivation and research purpose 3 Chapter 2 Instruments Introduction 5 2.1 Scanning Electron Microscopy (SEM) 5 2.2 X-ray Diffraction (XRD) 6 2.3 Photoluminescence (PL) 7 2.4 Focus Ion Beam System (FIB) 9 2.5 Transmission Electron Microscopy (TEM) 10 2.6 Paper Review 12 Chapter 3 Experiment Method and Fabrication of CO Sensing Device 15 3.1 Fabrication of Znic Oxide Nanowire 15 3.1.1 Wafer Cleaning 16 3.1.2 Preparation of ZnO seed layer 17 3.1.3 Synthesis of ZnO nanowires 18 3.1.3.1 Synthesis of pure ZnO nanowires 19 3.1.3.2 Synthesis of metal doped ZnO nanowires 20 3.2 Fabrication of CO gas sensing device 22 Chapter 4 Material Properties 24 4.1 Morphology 24 4.1.1 FE-SEM 24 4.1.1.1 Pure ZnO nanowires 24 4.1.1.2 Mn doped ZnO nanowires 26 4.1.1.3 Mg doped ZnO nanowires 27 4.1.2 FE-TEM 30 4.1.2.1 ZnO NWs growing on Silicon 30 4.1.2.1 ZnO NWs growing on sapphire 31 4.1.3 EDS (SEM&TEM) 32 4.1.3.1 FE-SEM EDS 32 4.1.3.2 FE-TEM EDS 35 4.1.4 XRD 40 4.2 Optical-electric Properties 41 4.2.1 Raman spectrum 41 4.2.2 XP spectrum 44 Chapter 5 Device Properties and Sensing Results 47 5.1 I-V curve measuring 47 5.2 CO sensing Results 49 5.2.1 sensing results of single ZnO NWs growing on silicon 50 5.2.1.1 pure ZnO NWs on Si(100) 50 5.2.1.2 Mn doped ZnO NWs on Si(100) 51 5.2.1.2 Mg doped ZnO NWs on Si(100) 52 5.2.2 sensing results of single ZnO NWs growing on sapphire 53 Chapter 6 Conclusion 56 Reference 5