化學液體成膜的紫外光激二氧化鈦氣體感測器

Abstract

本研究提出一個氣相層析技術後端偵測器的設計。利用金屬氧化物半導體氣體感測器使用壽命長，高靈敏度，適用多氣體偵測的特點，從Prof. Helwig提出金屬氧化物薄膜表面吸附水膜可用於在常溫環境偵測酸性，鹼性與短鏈醇類氣體分子的游離氣體感測機制出發，製作常溫操作的二氧化鈦薄膜氣體感測器。 本研究結合傳統微機電製程與溶膠凝膠法，以圖形化光阻作為金(Au)濕蝕刻阻擋層，在蒸鍍金的熱氧化矽晶片上，製作感測用的指叉電極。溶膠凝膠法混合作為溶劑的去離子水，作為催化劑的冰醋酸，與作為先驅物的異丙氧化鈦(titanium isopropoxide, TIP) ，配置薄膜生成材料，靜置待水解、縮合反應完成後產生透明的二氧化鈦溶膠。接著在指叉電極間隙塗布溶膠，熱處理後生成二氧化鈦感測薄膜。 實驗時將晶片裝置在氣相層析儀分離管柱末端，以乾燥空氣作為載子氣體(carrier gas)推動待測氣體樣品使其在管柱中分離成氣體帶，依序與二氧化鈦偵測薄膜接觸，產生訊號。從量測訊號發現，本研究製作的二氧化鈦偵測薄膜在常溫環境可偵測到文獻所載酸，鹼性水解氣體與短鏈醇類之外，更多樣的氣體種類。感測器經過紫外光的照射後，可使小分子量酯類、乙醚結構、甲苯分子的訊號更清晰。

In this study, the design of an end point detector for gas chromatography (GC) system was developed. The metal oxide (MOX) semiconductor type gas sensor was chose because of its long life time, high sensitivity and broad selectivity. Starting from Prof. Helwig’s dissociative gas sensing mechanism, adsorbed water layers on the metal oxide surface assisted the detection of acidic gases, basic gases and short chain alcohols at room temperature. This study focused on the development of a room-temperature-operated gas sensor with the titanium dioxide sensing film by the chemical solution process. Sensors were fabricated by the combination of both conventional micro electro mechanical systems (MEMS) technology and the sol gel method. Gold metal layer deposited on thermally oxidized silicon wafer was patterned by lithography. With photoresisit were used as stop layer of wet etch process to gold, exposing interdigit electrodes on silicon subtract. To prepare materials used for the formation of the sol, the deionized water used as solvent, the acetic acid served as catalyst, the titanium isopropoxide, (TIP) utilized as precursor, were mixed. After the hydrolysis reaction and condensation reaction are done, the transparent TiO2 sol was formed. The sol was deposited on gaps between interdigit electrodes of the sensor. With the high temperature annealing, sol was transformed into TiO2 sensing film. To characterize the sensor performances, the sensor was placed at the end point of the separation column of a GC system. Dry air was utilized as the carrier gas to push the sample mixture through the column, separated into bands and was detected by the TiO2 film of the sensor at the outlet of the column. It is found that the TiO2 film has the capability to detect more types of gas molecules than previously reported acidic gases, basic gases and short chain alcohols at room temperature. With or after the irradiation of ultraviolet light, signals of esters with a small molecular weight, molecule with ether-like structure and toluene are clear to distinguish.