NEW GAS-SENSING METHOD FOR DETECTING CARBON-MONOXIDE BY USE OF THE COMPLEX IMPEDANCE OF A CUO/ZNO HETEROCONTACT UNDER A DC BIAS VOLTAGE

The impedance characteristics of a CuO/ZnO oxide semiconductor heterocontact were investigated to study a new method of gas identification. This was done by applying a dc bias voltage in atmospheres of air-balanced, flammable CO or H-2 gas (4000 ppm). The frequency dependence of the reactance component showed a characteristic behavior that varied according to the testing atmosphere under the applied negative dc voltage at 400-degrees-C. The discrimination of CO gas from H-2 gas in air was demonstrated as feasible by either varying the bias voltage in negative values at constant frequency or sweeping the frequency on a negative bias voltage. The new method of gas identification suggested by the present study uses a ceramic-semiconductor heterocontact, on which a combination of dc bias voltage and ac signal is applied.