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 heteroc ontact were investigated to study a new method of gas identification. This was done by applying a dc bias voltage in atmospheres of air-bala nced, flammable CO or H-2 gas (4000 ppm). The frequency dependence of the reactance component showed a characteristic behavior that varied a ccording to the testing atmosphere under the applied negative dc volta ge 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 neg ative values at constant frequency or sweeping the frequency on a nega tive bias voltage. The new method of gas identification suggested by t he present study uses a ceramic-semiconductor heterocontact, on which a combination of dc bias voltage and ac signal is applied.