ELECTRICAL-CONDUCTIVITY OF POLYCRYSTALLINE SNO2(CU) FILMS AND THEIR SENSITIVITY TO HYDROGEN-SULFIDE

The effect of doping with copper on the sensor properties and the elec trical conductivity of polycrystalline SnO2(Cu) films has been investi gated. It has been found that at room temperature the residual conduct ivity is observed after the films are exposed to H2S. This made it pos sible to determine the character of the low-temperature conductivity o f the films for different degrees of saturation with hydrogen sulfide. A comparison of the obtained data with the results of layerwise eleme ntal analysis suggested a model that explains the mechanism of the gas sensitivity of SnO2(Cu) to hydrogen sulfide. In contrast to the mecha nisms, which are associated with the work done by the surface and whic h are standard for gas sensors, in the present case the change in the conductivity is due to the chemical reaction of the electrically activ e copper with sulfur in the entire volume of the film. This reaction d etermines the selectivity and high sensitivity of SnO2(Cu) to H2S. (C) 1997 American Institute of Physics.