| Summary: | 碩士 === 國立中山大學 === 電機工程學系研究所 === 106 === In this thesis, tin dioxide (SnO2) nanostructures are grown on silicon substrates by hydrothermal synthesis and sol-gel method. The fabricated nanomaterials are applied to ethanol gas sensors. Hydrothermal synthesis develops SnO2 nanoparticles on sputtered seed layer. Sol-gel method deposits SnO2 nanofilms on substrates through dip coating. We also utilize wet etching with potassium hydroxide (KOH) to change the surface morphology of silicon substrates. The etched surfaces with pyramid arrays have been effectively increased the surface-to-volume ratio. Larger area of the devices can react with more ethanol gas molecules and the response to gas are improved.
The experiments are performed by modifications of the chemical formulas and the cycle numbers of dip coating. The optimal parameters are acquired for ethanol gas sensing. According to the results, the device with SnO2 nanoparticles by hydrothermal synthesis on the etched substrate has the best sensing characteristics. The best device has a response of 379% under 200℃ and 300ppm ethanol gas. Besides, the response and recovery times are 17 seconds and 20 seconds, respectively. Compare with the planar device, the sensitivity of the device with pyramid arrays is well-enhanced. Wet etching changes the surface morphology and increases the surface area to react with ethanol gas. Moreover, the p-n junctions between the nanomaterials and the substrates have higher energy barriers and reduce the leakage currents of the devices. Ethanol gas sensors with high responses have superior potential for drunk driving evaluation and industrial safety inspection.
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