Humidity effect on baseline conductance and H2S sensitivity of cadmium germanium oxynitride thick film gas sensors

Cadmium germanium oxynitrides are excellent sensing materials for the detection of H2S. The effect of humidity on both the baseline conductance and on the sensitivity to H2S of thick-film gas sensors was investigated. The devices were subjected to dry and moist (varying relative humidity (RH)) air. Results showed that, unlike most semiconductor gas detectors, the presence of moisture has no significant effect on conductivity nor on the sensitivity to H2S of cadmium germanium oxynitride sensors. Hypotheses on surface processes accounting for such insensitivity are given. It appears likely that the surface states involved in responses to changes in RH are different from those involved in the detection of other gases.