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°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.