The EMOSFET as a potentiometric transducer in an oxygen sensor

Abstract

Oxygen concentrations have been measured using the so called ‘Clark cell’ for a long time. In this paper, first some drawbacks of the Clark cell are discussed, with special attention towards miniaturization of the sensor. Subsequently, the use of potentiometric sensors is discussed. In both the miniaturized Clark cell and in the potentiometric sensor a reference electrode is needed, which is hard to fabricate using thin film techniques. For this reason a novel way of carrying out potentiometric measurements, using a specially developed type of potentiometric oxygen sensor, is described. As the measurand the threshold voltage of a FET-structure having an iridium oxide gate is used, rather than the electrode potential. The potential advantages of such a sensor compared with the Clark cell are examined and the theoretical response of the sensor is derived. In addition some relevant experiments are described.