Gas sensing based on the dynamic nonlinear responses of a semiconductor gas sensor: dependence on the range and frequency of a cyclic temperature change

A novel gas-sensing system based on the multi-dimensional information contained in dynamic nonlinear responses is reported. A sinusoidal temperature change was applied to a semiconductor gas sensor, and the resulting conductance of the sensor was analyzed by fast Fourier transformation (FFT). The higher harmonics of the FFT characterized the nonlinear properties of the response at the sensor surface. The amplitudes of the higher harmonics exhibited characteristic changes which depended on the kinetics of the gas species on the sensor surface, and on the range and frequency of the cyclic change in temperature. The characteristic nonlinear response of a gas sensor which depends on the range of a cyclic change in temperature is discussed in relation to the kinetics of gas molecules at the sensor surface.