Rhythmic chemical reaction of CO on the surface of a SnO2 gas sensor

The oscillatory phenomenon of the oxidative reaction of CO on an n-type semiconductor surface is reported. As a semiconductor, we used a SnO2 gas sensor, which is widely used for practical application. Various characteristics in the time series of the conductance were observed and analyzed with next amplitude mapping and Fourier power spectra. The simultaneous measurement of the temperature on the semiconductor surface and the conductance suggested that the temperature change was a key variable in the oscillatory phenomenon. As a preliminary theoretical model, a simulation was performed using the surface concentration of CO and the temperature as two independent variables. The present study is part of our attempt to use a time-dependent nonlinear response for the development of an intelligent sensor which mimics sensory mechanisms in living organisms.