CO 가스 측정을 위한 ZnO 나노선 Gas 센서 제작 및 특성에 관한 연구
A Study on Fabrication and Characterization of Gas Sensor based on ZnO nanowires for CO Gas Detection
- 주제(키워드) ZnO nanowire , Vapor-Liquid-Solid(VLS) , CO 가스센서 , 반도체형 가스센서
- 발행기관 고려대학교 대학원
- 지도교수 문병무
- 발행년도 2012
- 학위수여년월 2012. 2
- 학위구분 석사
- 학과 일반대학원 전기전자전파공학과
- 세부전공 전자전기컴퓨터공학전공
- 원문페이지 61 p
- 실제URI http://www.dcollection.net/handler/korea/000000032580
- 본문언어 한국어
- 제출원본 000045697546
초록/요약
A Study on Fabrication and Characterization of Gas Sensor based on ZnO nanowire for CO Gas Detection Kangmin Do Dept. of Electrical Engineering The Graduate School Korea University Supervised by Professor, Byung-Moo Moon, Ph. D. Abstract ZnO is a promising material since it could be applied to many fields such as solar cell, laser diodes, thin-film transistor and gas sensors. ZnO has a wide and direct band gap of ~3.37 eV at room temperature and high exciton binding energy of 60 mV. In particular, ZnO nanowires (NWs) have received broad attention due to their distinguished performance in electronics, optics, and photonics. However, the control of density, diameter, and the length of ZnO NWs is still difficult for fabrication of various devices. Common ZnO NWs synthesis methods include metal-organic chemical, vapor deposition, vapor synthesis, hydrothermal, and chemical solution route. Generally, the NWs growth can be explained by vapor-liquid-solid(VLS) or vapor-solid (VS) mechanisms. In this study, we have synthesized ZnO NWs by using thermal evaporation method for CO gas sensor. The ZnO powder mixed with graphite in various weight ratio (1:1, 2:1, and 4:1) was used as a source material. A 5 nm thick -Au layer was deposited on a cleaned Al2O3 substrate for catalyst. The source powder and the substrates were placed inside the horizontal 1 inch diameter one-end closed tube and it was inserted inside an isothermal tube furnace. The furnace was heated at 1200 °C. Argon was flowed with a rate of 500 sccm and the growth pressure was kept constant at 80 mbar. To investigate the structural and morphological, X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and energy dispersive X-ray analysis (EDX) were carried out. XRD spectra show various orientations of ZnO nanowires at all samples. SEM images show that nanowires have different sizes and shapes. Aspect ratio is diameters between 70 and 110 nm and lengths between 0.9 and 1.5 μm. EDX spectra show atomic ratio of ZnO nanowires. No detectable Au along ZnO nanowire and it is strong evidence that ZnO nanowire have been grown by VLS mechanism and Au is just catalyst. At the gas concentration of 500 ppm CO, the sensor applied 2:1 source ratio exhibits improved sensitivity about 2 times than others. It is believed that source ratio promotes surface reaction of the gas molecules in the nanowire structure and hence the electrical conductivity and sensitivity were increased. We found that we can control shape and length of ZnO nanowire by different source ratio.
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Abstract ⅰ
기호 및 약어 목록 ⅴ
그림 목차 ⅵ
표 목차 ⅶ
1. 서 론 1
2. 이론적 배경 4
2.1 ZnO 특성 4
2.1.1 ZnO의 물리적 성질 4
2.1.2 ZnO의 전기적 성질 7
2.2 나노 물질의 특징 10
2.2.1 표면적 효과 10
2.2.2 양자 제한 효과 11
2.2.3 나노 물질의 중요성 12
2.3 가스센서 13
2.3.1 반도체형 가스센서 13
2.3.2 반도체형 가스센서의 감응 원리 17
2.3.3 반도체형 가스센서의 평가요소 20
2.3.3-1 반응 (response) 및 회복 (Recovery) 20
2.3.3-2 감도 (sensitivity) 20
2.3.3-3 선택성 (selectivity) 21
2.3.3-4 안정성 (stability) 21
2.4 반도체 나노선 합성 22
2.5 나노 구조물을 이용한 가스센서의 특성 23
2.6 입자 크기와 형상이 가스 감응성에 미치는 영향 25
3 실험 목적 및 방법 27
3.1 실험 목적 27
3.2 ZnO 나노선 합성 및 가스센서 소자 제작 27
3.2.1 나노구조성장 - VLS(Vapor-Liquid-Solid) 27
3.2.2 가스센서 소자 제작 및 측정 31
4. 실험 결과 33
4.1 ZnO 나노선 구조적, 화학적 성분 분석 33
4.2 CO 가스센서 특성 분석 39
5. 결 론 45
Reference 47
