多條奈米線電晶體之修飾與氣體感測

Abstract

本研究中將探討多晶矽奈米線於氨氣感測之特性，利用酞菁(Phthalocyanine)蒸鍍在奈米線場效電晶體上，經由修飾表面可提升奈米線對氨氣之感測效果。首先將選擇良好環境當基底做感測，可降低介電層被貫穿之機率。再者操作於低偏壓環境下，以及需控制大氣溼度在固定範圍下，以提升穩定性。感測機制有包括passivation effect及doping effect，氨氣會提供電子，提高n-type材料表面電性，造成奈米線表面離子交換，將填補奈米線晶界缺陷，此外蒸鍍修飾之厚度可經由AFM(原子力顯微鏡) 與SEM(掃描式顯微鏡)來做驗證。最後，經由修飾之多晶矽奈米線具備高度氨氣感測能力及選擇性，可感測0.5 ppm的氨氣，且可在室溫下進行操作，感測能力從1.38提升至2.16，操作電壓則位於-1 V至4 V，仍保有FET的特性表現。

The electrical properties of poly-silicon nanowires and surface modified by phthalocyanine materials nanowires were discussed in this study. The stable baseline was found in the most suitable environment condition, i.e. reduced pressure with controlled humidity. Low voltage stress was used to prevent the dielectric breakdown. Surface thickness and morphology were analyzed by SEM and AFM. Various aspects of sensing mechanisms, such as passivation effect and doping effect, can be applied to explain the experimental results. The electron pairs of ammonia molecules elevated drain current. Its surface exchanged ions and ammonia molecules filled the vacancy of poly silicon’s defect. Finally, the surface modified nanowires had high ammonia sensitivity and selectivity. Sensing ability of 0.5 ppm ammonia increased from 1.38 to 2.16 with the stable FET feature at the range of voltage stress from -1 V to 4 V at room temperature.