水熱法成長摻鎵氧化鋅奈米線應用於一氧化碳氣體感測之研究
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2010
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本研究係利用水熱法成長氧化鋅奈米線製成感測元件，並改變不同之鎵摻雜量，藉此探討一氧化碳氣體感測特性。首先，利用溶膠凝膠法製備氧化鋅材料，以旋轉塗佈製備一層氧化鋅種子層，加以進行不同溫度的退火處理，再以此當作基底成長氧化鋅奈米線，再探討其CO感測特性。實驗結果發現，種子層經500 C退火處理後成長的奈米線具有最佳(002)優先成長方向而種子層經700 C 退火處理後成長的氧化鋅奈米線可得到最佳長寬比，且在感測溫度250 C、CO濃度為200 ppm時具有最佳的感測靈敏度。另一方面，本研究分別以500 C及700 C退火種子層當作基底，在水熱法環境分別摻雜0.5 at. %、1 at. %、2 at.%的硝酸鎵成長氧化鋅奈米線，發現摻鎵濃度增加，氧化鋅奈米線的長寬比會降低，且經由700 C退火處理成長摻雜0.5 at. %硝酸鎵氧化鋅奈米線在感測溫度200 C時具有最佳的感測靈敏度，可達到12.64。最後，藉由改變水熱法溫度成長摻鎵氧化鋅奈米線，發現種子層700 C退火當作基底，在85 C條件下成長摻鎵氧化鋅奈米線具有最佳的長寬比，在感測溫度200 C時具有最佳的CO感測靈敏度為14.48。
This research uses sol-gel method for producing ZnO thin films as seed layers to prepare ZnO nanowires. The seed layers accept annealing treatment at different temperature to obtain crystal structure. A low-temperature solution process is used on the ZnO seed layer to construct a well-collimating, high length-diameter ratio array of nanowires. Sensitivity of CO gas sensing is expected to increase by applying the array of nanowires. According to the experimental results, ZnO nanowires have (002) preferential orientation when grown on the seed layers annealed at 500 C. However, it can obtain the better length-diameter ratio of nanowire when the nanowires grown on the seed layers annealed at 700 C. This nanowire array is applied on gas sensor can get the best sensitivity at the test temperature of 250 C when CO gas concentration is 200 ppm. Furthermore, the effects of Ga-doped ZnO (GZO) nanowires applied on gas sensor have been discussed. It can be found that the length-diameter ratio of ZnO nanowires decreases with Ga-doping concentration. When GZO nanowires with doping 0.5 at. % Ga grown on the seed layer annealed at 700 C, it can obtain the maximun length-diameter ratio of nanowire and reduce the best sensitivity temperature to 200 C. Finally, the sensing sensitivity can be improved by alter the heating temperature to 85 C during the hydrothermal process.
This research uses sol-gel method for producing ZnO thin films as seed layers to prepare ZnO nanowires. The seed layers accept annealing treatment at different temperature to obtain crystal structure. A low-temperature solution process is used on the ZnO seed layer to construct a well-collimating, high length-diameter ratio array of nanowires. Sensitivity of CO gas sensing is expected to increase by applying the array of nanowires. According to the experimental results, ZnO nanowires have (002) preferential orientation when grown on the seed layers annealed at 500 C. However, it can obtain the better length-diameter ratio of nanowire when the nanowires grown on the seed layers annealed at 700 C. This nanowire array is applied on gas sensor can get the best sensitivity at the test temperature of 250 C when CO gas concentration is 200 ppm. Furthermore, the effects of Ga-doped ZnO (GZO) nanowires applied on gas sensor have been discussed. It can be found that the length-diameter ratio of ZnO nanowires decreases with Ga-doping concentration. When GZO nanowires with doping 0.5 at. % Ga grown on the seed layer annealed at 700 C, it can obtain the maximun length-diameter ratio of nanowire and reduce the best sensitivity temperature to 200 C. Finally, the sensing sensitivity can be improved by alter the heating temperature to 85 C during the hydrothermal process.
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水熱法, 氧化鋅奈米線, 鎵, 一氧化碳, 氣體感測, hydrothermal, ZnO nanowires, Ga, CO, gas sensing