矽奈米線元件應用於有機溶劑氣體感測之研究

Abstract

本研究利用自發性電化學蝕刻方式在矽基板上製備矽奈米線陣列，透過改變蝕刻時間來製作不同長度的矽奈米線，並將其應用於有機溶劑氣體之感測。實驗結果發現，蝕刻時間增加，矽奈米線長度也會隨之增加。且對於有機溶劑氣體感測之靈敏度，也隨著線長愈長而靈敏度愈好。本研究中並討論有機溶劑氣體分子與矽奈米線表面的反應性，在生活中常見的有機溶劑，本研究選用不具有極性且沒有孤對電子的正戊烷和正己烷，以及具有極性且有兩對孤對電子的甲醇、乙醇和丙酮作為待測有機溶劑。醇類具有由-OH官能基所產生的分子間氫鍵，而丙酮不具氫鍵但含有羰基(C=O)，研究結果顯示矽奈米線對含有羰基之丙酮有最好的反應性及感測靈敏度，而對烷類氣體則感測效果不佳。進一步製作N型與P型矽奈米線比較感測性質差異，結果顯示載子為電子的N型試片在感測過程中電阻值會下降；而載子為電洞的P型試片電阻值則會上升，進一步透過高摻雜之P型與N型試片來做感測並且探討感測機制與提升效果。最後透過Elovich吸附方程式發現在感測初期時圖形呈現線性行為，換算之電流差值越小則代表感測效果越好。Herein this study reports the preparation of silicon nanowires by using the electroless chemical etching method. Different lengths of silicon nanowires array can be obtained by changing the etching time. These arrays are used as sensors in detection of volatility organic solvents. We can obtain the longer length of silicon nanowires by increasing the etching time. The sensitivity of organic solvents will be increased depending on the length of silicon nanowires. We choose n-pentane, n-Hexane, methanol, ethanol and acetone as the organic solvents and report the reactivity between that and silicon nanowires. n-Pentane and n-Hexane is an non-polar solvent. There are hydrogen bonds between alcohol molecules causing by the OH functional group and carbonyl group was contained in acetone molecule. Both of these solvents are to be provided with polar. We can obtain the results in good reactivity and sensitivity of acetone which is containing carbonyl group. We compare n-type and p-type sensing result, n-type’s resistance are dropping and p-type’s resistance are rising; To discuss the sensing principle and rising sensing effect via P+ and N+ substrate. On sensing initial stage, we can be obtained by Elovich function to find they are linear, and it means when the current are small, the sensitivity are good.