現今的社會當中，軟性元件在學術界和業界都引起了極大的關注。為了適應在元件越做越小、性能越來越強的這個時代，擁有高彈性、高耐久度、性質優異的可靠元件是每個人共同追求的目標。軟性元件例如壓力感測器、彎曲感測器、光感測器、氣體感測器等等都有極高的需求。
而本次研究將會將目標放在製作出性能優秀的軟性光偵測元件。軟性光偵測元件可以被大量應用於現今的自駕車、無人機、穿戴式電子裝置之中。因此軟性光偵測器的可彎曲程度、耐久度、高靈敏性便成為重要的參考依據。
本研究將會將重點放在如何順利地利用簡單的化學氣相沉積製程來生長出硫化鎘奈米線，並且確認其物理、光電性質表現。此後利用氧化鋅生成type2的異質結構，並且利用簡單的轉移法將奈米線轉移至軟性的聚醯亞胺基板(PI)來形成金屬-半導體-金屬的光偵測器。光偵測器會在紅綠藍三種不同波段及不同強度下的光源下進行量測，並且軟性光偵測器的彎曲測試與耐久度測試都會被測試。
以結論來說，以硫化鎘為基底的軟性光偵測元件表現出優異的光感測開關特性和高元件反應速度。此外聚醯亞胺基板(PI)更是提供了優異的元件穩定度，在高彎曲角度與高彎曲次數下元件都保持良好的光偵測特性。這些結果都指出本研究合成的高質量硫化鎘奈米線與元件製作方法為實際應用於生活中帶來可能性。

In recent years, flexible components have aroused great attention in both academia and industry. In order to adapt to this era of increasingly miniaturized components and stronger performance, it is prudent to fabricate reliable components with high elasticity, high durability, and excellent properties. Flexible components such as pressure sensors, bending sensors, photodetectors, gas sensors, etc. are in extremely high demand.
Flexible photodetectors have been widely used in today's self-driving vehicles, drones, and wearable electronic devices. The flexibility, reliability, and high sensitivity of the flexible light detection components are important criteria. The present work focused on the fabrication of flexible light detection components with excellent performance.
CdS nanowires have been successfully synthesized with a simple chemical vapor deposition process. Their physical and optical properties were characterized. Afterwards, zinc oxide was deposited on CdS nanowires to form a typeⅡ heterostructure, and a simple transfer method was applied to transfer the nanowires to a flexible PI substrate to form a metal-semiconductor-metal photodetector. The photodetector has been measured under light sources of different wavelengths and different intensities. The bending and reliability tests of the flexible photodetector were also carried out.
The CdS-based flexible photodetector exhibits excellent on-off photo-switching characteristics and high photo-response speed. In addition, the PI substrate provides excellent device stability, and the device maintains great performance under high bending angles and high bending cycles. These results indicate that the fabrication of flexible transparent photodetectors based on high-quality CdS-ZnO nanowires is very promising for practical applications in wearable devices.

Abstract I
摘要 III
誌謝 IV
Acknowledgments VI
Contents VIII
Chapter 1 Introduction 1
1.1 Motivation 1
1.2 Overview of Nanotechnology 2
1.2.1 One-Dimensional Nanostructures 4
1.2.2 Synthesis of 1D Nanostructure 4
1.2.3 Vapor-Liquid-Solid (VLS) Growth Mechanism 6
1.3 Photodetector 8
1.3.1 Photoconductive Effect 9
1.3.2 Photoconductor 10
1.3.3 Photodiode 11
1.3.4 Key Parameter in Performance of Photodetector 13
1.4 Cadmium Sulfide 16
1.4.1 Properties of Cadmium Sulfide (CdS) 16
1.4.2 Structure of Cadmium Sulfide 17
1.4.3 Applications of CdS Nanostructure 18
1.5 Metal-Semiconductor Contact (MS Contact) 19
1.5.1 Ohmic Contact 21
1.5.2 Schottky Contact 22
1.5.3 Metal-Semiconductor-Metal Contact Photodetector 24
1.6 Heterostructure 25
1.6.1 CdS-ZnO Core-Shell Heterostructure Nanowires 27
Chapter 2 Experimental Procedures 28
2.1 Experimental Flowchart 28
2.1.1 Preparation of Substrates 29
2.1.2 Synthesis Procedures of CdS Nanowires and CZx nanowires 30
2.1.3 Fabrication of Single CdS Nanowire Photodetector 32
2.1.4 Fabrication of CZx Heterostructure Flexible Photodetector 34
2.1.5 Photoelectric Properties Measurements 36
2.2 Experimental Equipments 37
2.2.1 Three-Zone Furnace 37
2.2.2 Electron Beam Evaporation System 38
2.2.3 Spin Coater 40
2.2.4 Mask Aligner 41
2.2.5 Xenon Arc Lamp 43
2.3 Characterization Instruments 44
2.3.1 Scanning Electron Microscope (SEM) 44
2.3.2 Energy Dispersive Spectroscope (EDS) 46
2.3.3 X-Ray Diffractometer (XRD) 47
2.3.4 Transmission Electron Microscopy (TEM) 49
2.3.5 X-ray Photoelectron Spectroscopy (XPS) 51
2.3.6 UV-VIS Spectrometer 52
2.3.7 Photoluminescence (PL) 53
2.3.8 Probe Station and Semiconductor Characterization System 54
Chapter 3 Results and Discussion 55
3.1 Properties and Characteristics of CdS NWs 55
3.1.1 SEM Observation 55
3.1.2 EDS Analysis 56
3.1.3 XRD Analysis 57
3.1.4 TEM Observation 58
3.1.5 XPS Analysis 59
3.1.6 UV-VIS Absorbance Spectrum 60
3.1.7 PL Spectrum 61
3.2 Single CdS Nanowire Photodetector 62
3.2.1 Au-CdS-Au Structure 63
3.2.2 I-V Characteristics 65
3.2.3 Photoswitching Characteristics 67
3.2.4 Comparison of Single CdS 1D Photodetectors 70
3.3 CdS Based Flexible Photodetector 71
3.3.1 I-V Curves Characteristics 71
3.3.2 Photoswitching Characteristics 74
3.3.3 Reliability Characteristics 77
3.3.4 Comparison of Flexible Photodetectors 80
Chapter 4 Summary and Conclusions 81
Chapter 5 Future Prospects 83
5.1 Plasmon Enhancement of Photodetector on Plasmonic metals 83
5.2 Flexible 1D Nanostructure Photodetector 84
References 85

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