| Summary: | 碩士 === 國立交通大學 === 電子工程系所 === 98 === This article deals with an inverse problem of ion mixture composition estimation using electronic sensors based on conventional reference electrode (RE) and MOS transistors; this topic exactly is ion detection and interference of ISFET. As a result of higher sensitivity as well as selectivity of the sensing layer ZrO2 for some ion and the importance of H+, K+ and Na+ ions to human body mechanism, it reports the technological fabrication and the electrical characterization of ZrO2 ion sensitive field effect transistors (ISFET) for the detection of H+, K+ and Na+ ions. The device sensitivity to various ions is obtained by replacing the traditional transistor metal gate electrode with the series combination of the reference electrode, electrolyte and specific sensing layers, the first one is immersed the aqueous solution to detect the pH value and sensitive to the other ions in an electrolyte flowing over the gate.
So far as we know, ZrO2 ISFET chemical sensors show quasi-nernstian pH response with sensitivities around 58 mV/pH. Its detection yield is 98% compared to the Nernst equation. However, it is not our main goal for pH response as well as selectivity of the membrane (i.e. sensing layer) ZrO2 is limited and ions other than the main one also influence the measurement in complex solutions. Therefore, in this study, we will first investigate K+ and Na+ ions measurement in acid or base solution, that is, pK and pNa measurement. By way of evidencing, sensitivities of K+ and Na+ ions is lower than 20 mV/pH and non-nernstian pH-dependent phenomena for highest K+ or Na+ ions concentrations (pK and pNa lower than about 3). It is shown that the detection properties of H+, K+ and Na+ ions are dependent on each other, being responsible for saturation effects for the highest concentrations.
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