Resistance noise spectroscopy of SnO2 thick-film gas sensors

This paper describes the methods and results of resistance noise spectroscopy applied to SnO₂ nanoparticle thick-film sensors operated at temperatures of 200, 300, 400, and 500°C At each temperature, the sensors were exposed to three hits of 50 ppm of NO, H₂S, or NH₃. Sensor noise was sampled before, during, and after each hit. Initial inspection of the results seemed to show unique responses to each gas. More careful analysis revealed that the spectra were shaped by flicker noise, thermal noise, and signal attenuation. Thermal noise and attenuation are primarily functions of sensor DC resistance. Flicker noise was shown to be partly a function of DC resistance, but could not be directly correlated to DC resistance due to other, undetermined parameters.