Effect of carbon monoxide on the capacitance-voltage characteristics of Pd-SiO2-Si MOS diodes

The effect of carbon monoxide on the capacitance-voltage characteristics of metal-oxide-semiconductor diodes of the Pd-SiO2-n-Si type and the time dependences of changes in the capacitance at fixed diode biases have been investigated. The change in the capacitance in a CO-air gas mixture, in contrast to other reducing gases, is nonmonotonic. During exposure to a gas atmosphere, the capacitance-voltage characteristics first shift to higher positive biases, then regain their initial values, and finally shift to lower biases. A sharp decrease in the capacitance during the first several seconds of a gas pulse is followed by a slower increase in capacitance to a new steadystate value, which depends on the carbon monoxide concentration. The results are explained taking into account the bridge and linear types of CO adsorption on a SiO2 surface.