Characterization of the (MOSFET)-M-E, a novel one-electrode chemical transducer for redox measurements

A sensor device consisting of a MOSFET with an iridium oxide gate contact a nd denoted an (MOSFET)-M-E is presented. When the gate of this device is in contact with an electrolyte, the iridium oxide can take part in a redox re action, enabling thermodynamic equilibrium between the electrons in the iri dium oxide and protons in the solution. The chemical potential of the elect rons in the bulk of the iridium oxide can be changed by oxidation or reduct ion of the material and is related closely to the iridium oxide work functi on. Since the threshold voltage, V-T, of the MOSFET depends on the work fun ction difference between the gate contact and the silicon bulk, it is influ enced also by the redox reaction. So if this sensor is connected to the app ropriate amplifier circuit, the redox reaction induces changes in the outpu t signal of the system due to changes in the threshold voltage, VT, of the MOSFET. It is shown on a theoretical basis how the output signal is influen ced by the redox reaction and this description of the device is supported b y measurement results. (C) 1998 Elsevier Science S.A. All rights reserved.