Competition between oxygen and water molecules on SiO2/P-doped Si surface: The electrical dipole evolution on water/oxygen-adsorbed oxide surface

The performance of gas sensors is greatly influenced under humidity environment due to the dynamic correlation between water and oxygen molecules. In this work, we utilize the charge trapping characteristic to study surface gas adsorption and demonstrate the competitive adsorption behaviors between oxygen and water vapor from the perspective of electrical dipole by observing the evolution of second harmonic generation (SHG). By analyzing the trapping time constant of time-dependent SHG spectrum, we propose a dynamic model of the way water molecules weaken oxygen adsorption and develop water adsorption layer. Results show that the electric field created by charge trapping would further align the water molecules and enhance the SHG intensity. Here, a viewpoint of analyzing the net surface dipole change due to the adsorption-desorption on SiO2 surface to realize the energy preferable state is presented and provides a pathway for solving the water-sensor interaction prob-lems in gas sensor.

Automated summary

The performance of gas sensors in humid environments is influenced by the interaction between water and oxygen molecules. This study investigates the competitive adsorption behaviors of oxygen and water vapor using the charge trapping characteristic and observing the evolution of second harmonic generation. By analyzing the trapping time constant, a dynamic model is proposed to explain how water molecules weaken oxygen adsorption and form a water adsorption layer. The results show that the electric field created by charge trapping can align water molecules and enhance the second harmonic generation intensity. This research provides insights into solving water-sensor interaction problems in gas sensors by analyzing the net surface dipole change caused by adsorption-desorption on the SiO2 surface.