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논문요약 11

제1장 서론 13

제2장 이론적 배경 18

제1절 C-MEMS(carbon-micro electro mechanical systems) 18

1. C-MEMS의 정의 18

제2절 ALD (Atomic layer deposition) 19

1. ALD의 정의 19

2. ALD 증착 메커니즘 19

제3절 반도체식 가스센서의 특성 23

1. 반도체식 가스센서의 정의 23

2. 반도체식 가스센서의 원리 23

3. 반도체식 가스센서의 특성 26

4. 촉매작용 29

제4절 ZnO 특성 및 나노 구조물 가스센서 31

1. ZnO의 물리적 특성 31

제3장 실험 및 측정방법 37

제1절 시편 제작 37

1. C-MEMS 구조 형성 37

2. C-MEMS 기반 ZnO film 전극 표면 개질 43

3. ALD-ZnO 증착을 통한 H₂ gas sensor 소자 제작 50

제2절 시편 분석 54

1. C-MEMS 기반 post 분석 54

2. ALD-ZnO film 분석 54

3. 수소 센서 특성 58

제4장 결과 및 고찰 60

제1절 C-MEMS 기반 post 구조 분석 60

1. PR post SEM 분석 60

2. Pyrolysis 공정 후 carbon post 의 SEM 분석 62

제2절 C-MEMS 기반 ALD-ZnO film 분석 67

1. C-MEMS 기반 ALD-ZnO film 전극 표면 개질 분석 67

2. ALD-ZnO/C-MEMS 수소 센서 특성 분석 77

제5장 결론 82

참고 문헌 84

ABSTRACT 87

List of Tables

Table. 2-1. Comparison of various thin filmdeposition methods. 22

Table. 2-2. The physical properties of ZnO. 34

Table. 3-1. 2-step pyrolysis process condition. 41

Table. 3-2. ALD-ZnO process condition. 45

Table. 4-1. Carbon post dimensions before and after the pyrolysis process. 63

List of Figures

Fig. 1-1. (a) Nanowire, (b) Nanotube, (c) Nanoribon, and (d) Nanorod. 16

Fig. 1-2. (a) C-MEMS Li battery and (b) C-MEMS electrode. 17

Fig. 1-3. C-MEMS process. 17

Fig. 2-1. Schematic illustrate of atomic layer deposition (process). 21

Fig. 2-2. Space charge layer on the surface of an n-type semiconductor: (a) distribution of charge, (b) band scheme near conduction band edge, and (c) electron concentration in the conduction band. 25

Fig. 2-3. (a) Fast step wise increases and decreases of the partial pressure P₁ and P₂ of two different components. (b) and (c) show typical measuring signals deduced from different gas sensors as the result of changes according to (a). 27

Fig. 2-4. Hexagonal wurtzite structure of ZnO. 32

Fig. 3-1. Schematic diagram of E-beam & thermal evaporation system. 38

Fig. 3-2. Quartz tube furnace system used for a pyrolysis process. 41

Fig. 3-3. Schematic illustration showing the fabrication process flow of carbon post arrays: (a) substrate: Pt(3000Å)/Ti(200Å)/SiO₂(500Å)/Si, (b) SU-8 post arrays after patterning, and (c) carbon post arrays after pyrolysis. 42

Fig. 3-4. ALD system. 45

Fig. 3-5. Deposition rate of ALD-ZnO film as a function of the deposition temperature. 46

Fig. 3-6. Schematic illustration of carbon post arrays coated with ALD-ZnO film. 47

Fig. 3-7. Schematic diagram of the RF magnetron sputtering system. 49

Fig. 3-8. RTP (rapid thermal process) annealing system. 52

Fig. 3-9. Schematic illustration of ZnO modified carbon post arrays on top of Pt/Ti interdigitated electrodes. 53

Fig. 3-10. A packaged sensor (inset: ALD-ZnO/ glassy carbon posts on interdigitated electrodes). 53

Fig. 3-11. Schematic flow chart for TEM specimen preparation. 57

Fig. 4-1. SEM images of SU-8 post arrays. 61

Fig. 4-2. SEM images of the carbon posts formed on Au(3000Å)/Ti(200Å)/SiO₂(500Å)/Si substrate. 65

Fig. 4-3. SEM images of the carbon post array formed on Pt(3000Å)/Ti(200Å)/SiO₂(500Å)/Si substrate. 66

Fig. 4-4. TEM images of ALD-ZnO film on carbon post array: (a) top and (b) side regions of the carbon post. 68

Fig. 4-4. TEM images of ALD-ZnO/sputtered-ZnO film on carbon post array: (a) top and (b) side regions of the carbon post. 70

Fig. 4-6. TEM images and Zn concentration profiles measured from the EDS line scans obtained from (a) ALD-ZnO and (b) ALD-ZnO/sputtered-ZnO layers on the carbon post. A-B and C-D lines are the EDS scan lines and correspond to the x-axes of the right-side figures 73

Fig. 4-7. SEM images of surface roughness of ALD-ZnO films on both substrate. (a) ALD-ZnO/carbon, (b) ALD-ZnO/sputtered-ZnO/carbon. 75

Fig. 4-8. AFM images of surface roughness of ALD-ZnO films on both substrate. (a) ALD-ZnO/carbon, (b) ALD-ZnO/sputtered-ZnO/carbon. 76

Fig. 4-9. Carrier density of ALD-ZnO films as afunction of the film thickness. 78

Fig. 4-10. Sensor response of ALD-ZnO/carbon films. 80

Fig. 4-11. Sensor response of ALD-ZnO/carbon films: (a) ALD-ZnO film on planar electrode and (b) ALD-ZnO film on 3D carbon post electrode. 81