Study on the gas sensing properties of defect-controlled ZnO nanowire gas sensor
산소결함 농도 조절을 통한 ZnO 나노선 가스센서의 감응 특성에 관한 연구
- 주제(키워드) ZnO , nanowire , gas sensor , defect controll
- 발행기관 고려대학교 대학원
- 지도교수 이종흔
- 발행년도 2008
- 제출일 2008-07-07
- 학위수여년월 2008. 8
- 학위명 석사
- 학과 일반대학원 신소재공학과
- 세부전공 전자재료
- 원문페이지 57 p
- 본문언어 영어
- 제출원본 000045504461
초록/요약
Recently, one-dimensional (1-D) semiconductor nanostructures including nanowires, nanotubes, and nanobelts have attracted considerable interest for their potential as the building blocks for nano-scale devices. Due to the high surface-to-volume ratio, the 1-D nanostructures are regarded as the best candidate materials for the chemical/gas sensors, as demonstrated in SnO2-coated carbon nanotube, functionalized Si nanowires, ZnO nanowires. ZnO is a chemically and thermally stable n-type semiconductor with large exciton binding (60 meV) and bandgap energy (3.37 eV). With these properties, ZnO nanowires have widely been demonstrated as nano-scale ultraviolet (UV) lasers, light-emitting diodes, photo-detectors and chemical sensors. However, it is also well known that the optical/electrical properties of ZnO devices severely limited by the presence of native defects, which has been intensely investigated so far. Nevertheless there have been only few studies on native-defect effects on the gas sensing properties of ZnO-nanowire-based gas sensors. In this work, we will fabricate and characterize ZnO-nanowire-based gas sensors with a main emphasis on the effects of oxygen vacancy defects on the gas sensing properties. We fabricated a nanowire-based gas sensor using a simple method of growing ZnO nanowires bridging the gap between two pre-patterned Au catalysts, in which the electrical contacts to nanowires are self-assembled during the synthesis of nanowires. The gas sensing capability of this network-structured sensor was demonstrated using a diluted NO2. From photoluminescence (PL) measurements, however, we found that the defect concentration is sensitively dependent on the deposition parameters such as temperature, pressure, position, and synthesis process. Thus in order to control the defect concentration in ZnO nanowires, we will adopt post-annealing in O2 or H2 ambient. Secondly, we will characterize the electrical and optical properties of ZnO nanowires using the PL and current-voltage measurements. And finally, we will investigate the effects of native defects on the gas sensitivity, response and recovery time and propose the responsible mechanism for the correlation between native defects and gas sensing properties.
more목차
1. Introduction 1
2. Experimental process 3
2-1. Synthesis of ZnO nanowires 3
2-2. Fabrication of ZnO nanowire gas sensor 4
2-3. Post-annealing of ZnO nanowire 5
3. Results and Discussion 11
3-1. Growth and structure analysis of aligned ZnO nanowires 11
3-2. General gas sensing properties of ZnO nanowire gas sensor 17
3-3. Effects of native defects on gas-sensing properties 25
3-3-1. Native defects of as-fabricated ZnO nanowire gas sensor 25
3-3-2. Gas-sensing properties of defect-controlled ZnO-nanowire gas sensor 30
4. Conclusion 41
References 43
