Resistance and capacitance analysis of Pd-doped and undoped SnO2 thick films sensors exposed to CO atmospheres

It was found that resistance and capacitance of Pd-doped SnO2 thick films are largely modified by CO reaction with previous adsorbed oxygen at the grain surface while in undoped SnO2 thick-films adsorption and reaction processes influence the response. In our analysis, the presence of Schottky potential barriers at the grain boundaries was consistent with the observed results. An increasing of sensitivity due to the addition of Pd is found to be related to the enhanced reaction of CO with the previous oxygen adsorbed at the grains surface. Mechanisms responsible for the sensor response are discussed.