Characterizing the influence of gate bias on electrical and catalytical properties of a porous platinum gate on field effect gas sensors

In this work, we exposed an MIS capacitor with porous platinum as gate material to different concentrations of CO and NH
₃
. Its capacitance and typical reaction products (water, CO
₂
and NO) were monitored at high and low oxygen concentration and different gate bias voltages. We found that the gate bias influences the switch-point of the binary CO response usually seen when either changing the temperature at constant gas concentrations or the CO/O
₂
ratio at constant temperature. For NH
₃
, the sensor response as well as product reaction rates increase with bias voltages up to 6 V. A capacitance overshoot is observed when switching on or off either gas at low gate bias, suggesting increasing oxygen surface coverage with decreasing gate bias.