GaN과 TiO2를 이용한 유연지능재료 및 디바이스 응용

GaN과 TiO2를 이용한 유연지능재료 및 디바이스 응용
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This thesis demonstrates the device application possibility of flexible smart materials with Titanium dioxide (TiO2) and Gallium nitride (GaN). First of all, conductivity enhancement of a transparent flexible conductive material, Poly (3,4-rthylenedioxytiophene): poly (styrenesulfonate) (PEDOT:PSS?^for flexible device application was discussed. As first attempt, insulating PSS was eliminated from PEDOT:PSS matrix by HCl treatment, which increased more than a hundred times compared with pristine PEDOT:PSS. Secondly, multi wall carbon nanotubes (MWCNTs)-sorbitol composite was added to PEDOT:PSS. The PEDOT:PSS layer conductivity was thousand times higher than the pristine PEDOT:PSS. TiO2 thin film was fabricated by sol-gel process and three most important factors governing the grain size and phase transformation were discussed: annealing temperature, annealing time and film thickness. When the annealing temperature was below 850 0C with 120 minutes, no rutile phase was indicated. Depending on the annealing condition, the Schottky diode conduction mechanism was changed. The Schottky diode forward current was highly related with its phase and grain size. TiO2 can be applied to a sensor material at high temperature because of TiO2 surface area limitation for chemical molecule detection. To overcome the sensing capability problem, multi wall carbon nanotubes (MWCNTs) was introduced to improve the chemical sensitivity of TiO2 at room condition. TiO2 coated multiwall carbon nanotube was fabricated by hydrothermal method. The TiO2 nanoparticle with less than 5 nm diameters was well attached to the carbon nanotubes, where are three times larger surface areas compared with pristine TiO2 nanoparticles. By blending this inorganic composite to cellulose, flexible gas sensor, chemical vapor sensor and pH sensor were successfully fabricated that can be operated at room temperature condition. The ammonia (NH3) gas sensor and acetone chemical vapor sensors exhibit good sensitivity an
CHAPTER 1 INTRODUCTION 1.1 Flexible conductive material 1 1.2 TiO2 as a smart material 2 1.3 GaN as a smart material 3 1.4 Research objectives 4 1.5 Structure of thesis 4 CHAPTER 2 DEVELOPMENT OF HIGHLY CONDUCTIVE TRANSPRENT LAYER 2.1 Background 6 2.2 Fabrication of PEDOT:PSS layer by HCl treatment 9 2.3 Fabrication of PEDOT:PSS layer with MWNCT-sorbitol 10 2.4 Characterization of PEDOT:PSS layer by HCl treatment 11 2.5 Characterization of PEDOT:PSS layer with MWNCT-sorbitol 14 2.6 Summary 17 CHAPTER 3 TiO2 BASED THIN FILM SCHOTTKY DIODE 3.1 Background 29 3.2 TiO2 sol-gel thin film fabrication 31 3.3 Characterization: annealing temperature effect 32 3.4 Characterization: thickness effect 36 3.5 Characterization: annealing time effect 37 3.6 Schottky diode characterization 39 3.7 Summary 45 CHAPTER 4 TiO2 /MWCNTs BASED SMART MATERIAL AND DEVICES 4.1 Background 63 4.2 Fabrication of TiO2/MWCNTs blended cellulose hybrid film 65 4.3 Characterization 67 4.3.1 Characterization of TiO2/NWCNT composite 67 4.3.2 Characterization of CTM hybrid film 70 4.4 Flexible gas sensor 75 4.5 Flexible chemical vapor sensor 78 4.6 Flexible pH sensor 80 4.7 Summary 86 CHAPTER 5 GaN BASED NANOPARTICLE GAS SENSOR 5.1 Background 110 5.2 GaN nanoparticle fabrication 113 5.3 GaN nanoparticle Characterization 113 5.4 GaN nanoparticle as gas sensor 117 5.5 Summary 122 CHAPTER 6 CONCLUSIONS 137 REFERENCES 140 ACKNOWLEDGMENT LIST OF TABLES Table 3.1 The diffraction angle, the angular line width, and the grain size depend on film thickness 60 Table 3.2 Slope and beta values of the sol-gel driven TiO2 Schottky diodes depend on film thickness 60 Table 4.1 BET surface area result of different TiO2/MWCNTs products 107 Table 4.2 Summary of various metal oxide and CNT based material pH sensor 108 Table 5.1 BET surface area result of different GaN nanoparticle products 136 LIST OF FIGURES Figure 2.1 Chemical structure of PEDOT:PSS 19 Figure 2.2 Synthetic proces
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College of Engineering(공과대학) > Mechanical Engineering(기계공학) > Theses(기계공학 석박사 학위논문)
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