VOLTAGE-DEPENDENCE OF GAS-SENSING BEHAVIOR OF SNO2-GATE FETS

SnO2-gate FETs with ammonia-sensing behaviour are investigated at cons tant ammonia concentration (100 ppm) and different bias conditions. St rong 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 ba sis of the interpretation of the experimental data two conclusions are deduced: that the presence of ammonia in the air results in effective contributions DELTAV(G) to the V(G) applied electrically and that the working mechanism is generally dependent on the transversal electric field between the gate and the channel. However, there exists an addit ional dependence on V(D) and, thus, the observed sensing behaviour can not be explained by polarization or work function variations, or charg e storage effects originating from the transversal field alone.