Synthesis and electrical properties of SnO2-ZnO heterostructures
- 주제(키워드) nanowire , ZnO , SnO2 , PLD , T-PLD , hetero-junction , impedance analysis , equivalent circuit , photo-current
- 발행기관 고려대학교 대학원
- 지도교수 김규태
- 발행년도 2012
- 학위수여년월 2012. 8
- 학위구분 박사
- 학과 일반대학원 마이크로/나노시스템협동과정
- 원문페이지 183 p
- 실제URI http://www.dcollection.net/handler/korea/000000034964
- 본문언어 영어
- 제출원본 000045717875
초록/요약
It is very important that the fabrication of nano-materials and the device manufacturing for the resulted electrical properties of 1-dimensional nano-materials devices. It is also required that the study about their properties in detail in the changed stage of the dimension of semiconducting materials from 1-D to 3-D. In this paper, it was implemented that the growths of 1-D nanowires, 2-D film and the 3-D hierarchical structures and their physical and electrical characterization. It was suggested the newly designed T-PLD (thermal-assisted pulsed laser deposition) system and the fabricated materials analyses were proceed. Especially, it was invested that the impedance analysis of 3-dimensional hetero-junction structures for the detailed research about the junction properties. First of all, ZnO film was fabricated using PLD method. It was comparatively analyzed that the materials properties of ZnO films which were grown under the varied experimental growth conditions in PLD. The PLD system has been provided for the highly qualified ZnO film growth widely, so the films properties grown in PLD was investigated as changing the growth conditions systematically such as the gas pressure, laser conditions in my experiments. The interface properties between ZnO film and the sapphire substrate were investigated by using HR-XRD results. For the second, it was devised T-PLD system which has developed the existed PLD system. It was combined the advantages of the thermal energy in a furnace and the kinetic energy of the laser source which was evaluated as the major merit in PLD method. In this paper, ZnO nanowires were synthesized using T-PLD system and their materials properties were investigated in detail from the results of the low temperature PL analysis. The effect of the thermal energy on the growth of ZnO materials and the electrical properties of ZnO nanowire FETs were studied. Thirdly, it was comparatively investigated that the electrical properties of 1-dimensional and 3-dimensional nano-structures devices. By using T-PLD system, it was fabricated successfully the hetero-junction structures of the core-shell (p-Si NW/n-ZnO and SnO2 NWs/ZnO shell) structures or the hierarchical (SnO2 back-bone/ZnO branch) structures. The enhanced photo-current properties in 3-dimensional (SnO2-ZnO) structures were studied as suggesting the higher efficiency of electron-hole pair generation and the effect of water molecules. As the last thing, it was implemented DC/AC electrical analyses for the ZnO nanowire network devices. It was defined the device equivalent circuit model from the impedance analysis and the detailed characteristics of the devices under the UV irradiation to the active layer which could change the effects of elementary resistors or capacitors. In particular, it was investigated that the effects of the junction resistor or the junction capacitor in SnO2-ZnO network structures which is composed with 2-parrallel R-C equivalent circuits. It was mainly studied the effect of the materials junctions on the whole device electrical property in hetero-structured devices.
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Contents
Abstract
Chapter 1 Introduction 1
Chapter 2 Theoretical backgrounds 3
2.1 Junction 3
- Semiconductor junction 3
- Metal-Semiconductor junction 14
- Ohmic contact 19
2.2 Impedance spectroscopy (IS) 21
- EIS theory and physical electrochemistry 22
- Fourier transform 27
- Constant phase element (CPE) 27
2.3 Carrier mobility 33
- Drift carrier mobility 33
- Hall carrier mobility 35
- C-V characteristic for p-n junction 37
2.4 Photo conductivity 41
2.5 References 48
Chapter 3 Characterization of ZnO thin film grown by PLD 51
3.1 Introduction 51
3.2 Experimental Detail 53
3.3 Results and Discussion 55
- Growth of thin film 55
- Growth of nanowires 58
- XRD analysis 60
3.4 Conclusion 66
3.5 References 67
Chapter 4 Brush-shaped SnO2/ZnO hierarchical structures Synthesized Using Thermal-assisted PLD 71
4.1 Introduction 71
4.2 Experimental Detail 75
- T-PLD system 75
4.3 Results and Discussion 80
4.3.1 One step growth of ZnO nanowires 80
- Growth mechanism 85
- PL and XRD analysis 88
- Current-voltage property of ZnO nFET 96
4.3.2 Two-step growth of SnO2-ZnO hierarchy structures 98
- Photocurrent in SnO2-ZnO hierarchy structures 102
4.4 Conclusion 107
4.5 References 108
Chapter 5 Impedance analysis of the ZnO nanowire FET and SnO2-ZnO hierarchical devices 114
5.1 Introduction 114
5.2 Experimental Detail 115
- Transient Nyquist meter 117
5.3 Electrical properties of the ZnO and SnO2 nanowires FET 121
- Current-voltage characteristics 121
- Output and Transfer characteristics 123
- Impedance analysis of ZnO nFET under gate bias 127
5.4 Impedance analysis of the SnO2-ZnO NWs/p-Si device 138
- Current-voltage characteristics 138
- Impedance analysis SnO2 NWs/p-Si device 140
- Impedance analysis SnO2-ZnO/p-Si device 148
5.5 Conclusion 156
5.5 References 158
Chapter 6 Conclusions 165
