本研究係以銀修飾癸烷烴雙硫醇單分子層/金/砷化鎵蕭特基二極體作為氮氧化物(NOx)感測器，並探討其感測特性。實驗中，首先製備金/砷化鎵蕭特基二極體，接著導入烷烴雙硫醇單分子層於金電極上以作為NOx之感測材。為提升元件對NOx之靈敏度，進一步以銀修飾單分子層之末端官能基製成感測元件，探討銀離子浸泡濃度對元件感測特性之影響，並針對氣體種類、濃度及操作溫度等操作變因來加以探討。

實驗結果顯示，癸烷烴雙硫醇單分子層/Au/GaAs對NO2及NO之感測靈敏度分別為49.5及35.3；此元件經銀修飾後，對NOx之感測靈敏度有顯著提升，且隨著浸泡液銀離子濃度之升高而增大。當銀濃度1.0mM以上時，單分子層銀含量亦達到飽和值，此元件對NO2、NO之靈敏度分別提升到133.4、45.1。另外，感測靈敏度隨NOx濃度之增加而增大，且呈現良好的正比關係。當操作溫度範圍在25-110℃，發現靈敏度隨著溫度之上升而下降，亦即25℃時之靈敏度為最大。由選擇性實驗結果顯示，銀修飾之元件對氨氣、氫氣及一氧化碳無明顯之響應，亦即元件對氮氧化物有極高之選擇性。將背景氣體由氮氣更換為空氣時，元件對NOx之感測特性幾乎不變。

文中並提出一吸附動力模式來描述感測行為。實驗結果顯示，元件對NOx之感測行為遵循文中所提之模式，據此估算出元件對NO2吸附之正、逆向反應活化能分別為15.47、9.31kJ/mol；而對NO之吸附則分別為15.33、9.67kJ/mol；另外，NO2、NO之吸附熱則分別為6.16、5.66kJ/mol。

In this work, novel nitrogen oxides (NOx) sensors based on silver-modified alkanedithiol/Au/GaAs Schottky diodes were fabricated and studied. Experimentally, Au/GaAs Schottky diodes were firstly fabricated followed by introducing alkanedithiol monolayer on the Au electrode for NOx sensing. In order to promote the NOx sensitivities, the device was further modified with silver in the terminal group of the monolayer. The effect of silver concentration of the immersion solution on the sensing characteristics was investigated. Furthermore, the sensing characteristics of the Ag-modified devices toward nitrogen oxides were studied under various gases, concentrations, and temperatures.

From the experimental results, it revealed that the sensitivities of decanedithiol/Au/GaAs device toward NO2 and NO were 49.5 and 35.3, respectively. After modifying with silver, the device showed a large promotion in NOx sensitivities which have the increasing trend as the silver concentration was increased. When the silver concentration increased above 1.0 mM, the silver content in the monolayer reached to a saturation value. The sensitivities of this device toward NO2 and NO were largely promoted to 133.4 and 45.1, respectively. Besides, the sensitivities increased with increasing NOx concentration and were in good proportional to the NOx concentrations. In the operating temperature range of 25-110℃, the NOx sensitivities of the device decreased with increasing the sensing temperature, i.e., the maximum sensitivities occurred at 25℃. The device also exhibited quite high selectivities toward NOx with respect to H2, NH3 and CO. As replacing the background ambience nitrogen by air, the NOx sensitivities remained without any obvious change.

A kinetic adsorption model also proposed in this work to describe the sensing behavior of the device. The result showed that the NOx sensing behavior obeyed the proposed model well. Basing on the model, the activation energies of the forward and reverse adsorption reaction for NO2 were determined as 15.47、9.31kJ/mol, respectively, and those for NO were 15.33、9.67kJ/mol, respectively. Besides, the adsorption enthalpies of NO2 and NO were determined as 6.16、5.66kJ/mol, respectively.

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