| Summary: | 碩士 === 國立交通大學 === 電子物理系 === 91 === 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.
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