Abstract
The works presented in this thesis discuss the preparation and characterization of the one-dimensional (1D) SnO2 and ZnO nanostructures for the gas- and photon-sensing applications. To enhance the gas- and photon-sensing properties of these nanostructures, many processes were employed to improve the sensitivity, response and recovery speed of the nanostructure-based sensors, including doping, surface functionalization and incorporation of heterostructures. These methods provide efficient routes for strongly enhancing the sensing properties of semiconducting nanostructures and fabricating sensors that are highly sensitive, responsive, and concentration selective. Thus, they can be expected to be applied in the future. In Chapters 3 and 4, we report that fluorinated SnO2 nanowires can be achieved by the surface fluorination using CF4 plasma. The fluorinated SnO2 nanowires exhibited a much lower electrical resistance, as compared with pure SnO2 nanowires. In addition, the sensors fabricated from the fluorinated SnO2 nanowires performed high photon-sensing ability ethanol gas sensitivity. In Chapter 5, Pt nanoparticles were deposited on SnO2 nanowire surface by ALD to enhance the gas-sensing properties. The growth mechanism of the Pt nanoparticles on nanowires was also investigated. The Pt/SnO2 core-shell nanowires were also prepared by a process that involves thermal evaporation of Pt and subsequent ALD of Pt, which exhibited high electrical conductivity, gas sensitivity and response speed. The Pt/SnO2 core-shell nanowires are therefore suitable to be used as gas sensors and photodetectors (Chapter 6). Additionally, the photon-sensing properties of ZnO nanowires are remarkedly improved after the ALD of Pt nanoparticles on their surface (Chapter 7). Furthermore, the nanocomposites fabricated by ALD of ZnO nanoparticles on acid-treated MWCNTs have applications in UV photodetectors. Two different types of ZnO-CNT-based photodetectors were produced by alternating the ALD reaction cycles, and the behaviour of p- to n-type conversion was found to be attributable to the increase in the amount and surface coverage of ZnO on CNTs. Finally, we conclude the results of our experiments and propose some practicable research directions.

摘要
本論文研究著重於探討一維金屬氧化物奈米結構物做為感測材料的性用特性，並藉由摻雜、表面功能化、加入金屬觸媒及合成奈米級複合材料等方式提升其材料特性。藉由四氟化碳（CF4）電漿處理後的氧化錫奈米線，氟原子可被成功地摻雜入奈米線表面，並因而提升奈米線的導電性、光子感測性與低溫的酒精氣體感測性 （詳見第三、四章）。於第五章中，本論文藉由原子層沉積技術將白金奈米金屬顆粒沉積於氧化錫奈米線表面，並探討白金奈米金屬顆粒在氧化錫奈米線上的成長方式，並大幅提升其氣體感測特性。此外，同樣利用此技術合成白金與氧化錫的奈米線殻核結構，使其具備高導電性、高氣體敏感性、快速反應等特性，因而可作為氣體與光子的感測器應用（詳見第六章）。若利用原子層沉積技術將白金觸媒沉積於氧化鋅奈米線表面，將可大幅提升其光子感測特性（詳見第七章）。另外，藉由原子層沉積技術，於酸處理後的多壁奈米碳管表面成長無機氧化鋅晶粒，此奈米複合材料可應用於UV光的感測應用，如果原子層沉積的反應循環次數改變，將改變氧化鋅在奈米碳管的數量與覆蓋率，因而改變其感測特性（p、n型半導體轉變；詳見第八章）。最後，對於本研究論文給予一結論，並提出未來可行的研究規劃。

Contents
Abstract..........................................................................................................................I
Acknowledgement.…………………………………………………………………IV
Contents.........................................................................................................................1

Chapter 1 Introduction………………………………………………………….1
1-1 Brief introduction of tin oxide nanostructures…………………………………1
1-1-1 Crystal structure and physical characteristic of tin oxide
1-1-2 Preparation and growth mechanism of tin oxide nanostructures
1-1-2-1 Vapor-liquid-solid (VLS) mechanism
1-1-2-2 Vapor-solid (VS) mechanism
1-1-2-3 Solution-liquid-solid (SLS) mechanism
1-1-3 Novel nanostructures and potential applications of tin oxide nanostructures
1-2 Brief introduction of zinc oxide nanostructures………………………………..9
1-2-1 Crystal structure and physical characteristic of zinc oxide
1-2-2 Preparation, growth and applications of zinc oxide nanostructures

Chapter 2 Experimental Section…………………………………………..…22
2-1 Horizontal furnace system……………………………………………………..22
2-1-1 The preparation of pristine SnO2 nanowires by thermal evaporation
2-1-2 The preparation of pristine ZnO nanowires by thermal evaporation
2-2 Plasma treatment by microwave plasma enhanced chemical vapor deposition system………………………………………………………………………………..24
2-3 Atomic layer deposition system……………………………………………...…27
2-3-1 Atomic layer deposition of Pt on nanowire surface
2-3-2 Atomic layer deposition of ZnO on nanostructure surface
2-4 Characterization……………………………………………………………..…30
2-4-1 Field emission scanning electron microscopy (FESEM)
2-4-2 High-resolution transmission electron microscopy (HRTEM)
2-4-3 X-ray diffraction (XRD)
2-4-4 Nano-Auger electron spectrometer spectroscopy
2-4-5 X-ray photoelectron spectroscopy (XPS)
2-5 Gas- and Photon-sensing measurements…………………………………....…32
Chapter 3 The Preparation and High Photon-sensing Properties of Fluorinated Tin Dioxide Nanowires…………………………………………36
3-1 Background and motivations…………………………………………………..36
3-2 Experimental……………………………………………………………………37
3-3 Results and Discussion………………………………………………………….38
3-4 Summary………………………………………………………………………...46
Chapter 4 Fabrication, characterization and ethanol gas sensing properties of fluorinated SnO2 nanowires………………………………....50
4-1 Background and motivations…………………………………………………..50
4-2 Experimental……………………………………………………………………51
4-3 Results and Discussion…………………………………………………………53
4-4 Summary………………………………………………………………………...63
Chapter 5 Fabrication of Tin Dioxide Nanowires with Ultrahigh Gas Sensitivity by Atomic Layer Deposition of Platinum……………………67
5-1 Background and motivations…………………………………………………..67
5-2 Experimental……………………………………………………………………69
5-3 Results and Discussion………………………………………………………….70
5-4 Summary………………………………………………………………………...85
5-5 Supporting Information………………………………………………………..91
Chapter 6 Preparation of Pt/SnO2 Core-shell Nanowires with Enhanced Ethanol Gas- and Photon-Sensing Properties………………94
6-1 Background and motivations…………………………………………………….94
6-2 Experimental…………………………………………………………………....94
6-3 Results and Discussion………………………………………………………….97
6-4 Summary……………………………………………………………………….110
Chapter 7 Highly Sensitive ZnO Nanowire Photodetector with Atomic Layer Deposited Platinum…………………………………….…...115
7-1 Background and motivations………………………………………………………..115
7-2 Experimental……………………………….…………………………………………..116
7-3 Results and Discussion……………………………………………………………….118
7-4 Summary………………………………………………………………………………..124
Chapter 8 Atomic Layer Deposition of Zinc Oxide on Multiwalled Carbon Nanotubes for UV Photodetector Applications………...…….128
8-1 Background and motivations……...………………………………………….128
8-2 Experimental…………………………………………………………………..130
8-3 Results and Discussion………………………………………………………...131
8-4 Summary……………………………………………………………………….142
Chapter 9 Conclusions……………………………………………………...147
Chapter 10 Future works…………………………………………………..150

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