THE (MOSFET)-M-E AS A POTENTIOMETRIC TRANSDUCER IN AN OXYGEN SENSOR

Oxygen concentrations have been measured using the so called 'Clark ce ll' 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 discuss ed. In both the miniaturized Clark cell and in the potentiometric sens or a reference electrode is needed, which is hard to fabricate using t hin him techniques. For this reason a novel way of carrying out potent iometric measurements, using a specially developed type of potentiomet ric oxygen sensor, is described. As the measurand the threshold voltag e of a FET-structure having an iridium oxide gate is used, rather than the electrode potential. The potential advantages of such a sensor co mpared with the Clark cell are examined and the theoretical response o f the sensor is derived. In addition some relevant experiments are des cribed. (C) 1998 Elsevier Science S.A. All rights reserved.