Dependence of sensitivity of SnOx thin-film gas sensors on vacancy defects

Oxygen flow during dc reactive sputtering of SnOx thin films affects film conductivity in zero grade air and gas sensitivity to carbon monoxide and ethanol. The experimental results show that an increase in oxygen flow during film deposition produces films exhibiting higher conductivity in zero grade air and lower gas sensitivity. A theoretical model is presented that explains this behavior. The proposed model takes into account both the dependence of conductivity on the potential barrier height at grain boundaries of the film and the dependence of chemisorption rate of oxygen on free-electron availability. The theoretical analysis is in good qualitative agreement with experiment. (C) 1996 American Institute of Physics.