Voltage dependence of gas-sensing behaviour of SnO 2-gate FETs

Abstract

SnO 2-gate FETs with ammonia-sensing behaviour are investigated at constant ammonia concentration (100 ppm) and different bias conditions. Strong dependence of the sensing behaviour on the drain and gate voltage ( V d , V g ) applied is observed. The current response obtained could be positive, negative or zero at different bias conditions. On the basis of the interpretation of the experimental data two conclusions are deduced: that the presence of ammonia in the air results in effective contributions Δ V g to the V g applied electrically and that the working mechanism is generally dependent on the transversal electrical field between the gate and the channel. However, there exists an additional dependence on V d and, thus, the observed sensing behaviour cannot be explained by polarization or work function variations, or charge storage effects originating from the transversal field alone.