三氧化鎢/氧化銥二極體元件對pH值的感測研究

Abstract

本論文的內容主要介紹，以三氧化鎢╱氧化銥二極體為基礎的pH值感測器，我們在白金電極上先後鍍上三氧化鎢與氧化銥薄膜，並讓兩薄膜中間部分重疊，使得薄膜重疊的界面形成二極體架構，然後在其上再鍍一層氧化鋁薄膜作為表面修飾，這三種薄膜都以濺鍍的方式，使用剝落製程技術，最後以環氧樹脂封裝完成，本元件的工作機制，是由於三氧化鎢與氧化銥薄膜對pH值有感應，因為氫離子進入薄膜內，會使薄膜產生可逆式的氧化還原反應，而氧化鋁薄膜則可以阻絕溶液中氧化還原物質對量測造成影響，此pH值感測元件的電流，會對溶液的酸鹼度有反應，量測範圍pH 2 ~ 12，反應時間在10秒以內，此元件的優點是體積小，反應快重複性高，不需要額外的參考電極，使用材質穩定，製程便宜，而其缺點是在鹼性環境下反應變化量較小，還有電流對pH值的變化非線性。

This article reports the technological fabrication and the electrical characterization of pH sensors based on WO3╱IrO2 diode device. We have deposited WO3 and IrO2 thin films on platinum electrodes and the part these thin films were overlap. The interface of these thin films formed a diode structure. Then the films were coated with Al2O3 thin films to modify surface. These thin films are fabricated by the lift-off technique with reactive magnetron sputtering at deposition temperature 100℃ and these devices were package with epoxy. The mechanism of the pH sensors is based on pH-sensitive WO3 and IrO2, which interact with H＋ in the reversible redox reactions. The Al2O3 thin films can protect diode from redox species in the solutions. The pH sensors current responded reproducibly to the acidity changes of the analyte in the range of pH 2 ~ 12. Sensors responded within 10 seconds after being exposed to basic solutions. The advantages of these pH sensors include their ruggedness, small size, well reproducible, without reference electrode, and the low cost of fabrication. But some disadvantages are non-linear response and small current response in the pH region between 8 and 12.