Electrical field impact on the gas adsorptivity of thin metal oxide films

A thin semiconducting NiO film is exposed to ${\mathrm{NO}}_{\mathrm{2}}$ at room temperature. This exposure causes a work function change at the surface of the film due to adsorption of the ${\mathrm{NO}}_{\mathrm{2}}$ molecules. It is found that there is a strong dependence of the adsorptivity, i.e., the amount of work function change per unit time, on the magnitude of an electrical field that is applied perpendicular to the film surface. This induced adsorptivity change is known as the electroadsorptive effect. In order to modulate the adsorptivity significantly, the electrical field strength must exceed ${10}^4\hspace{0.17em}\mathrm{V/cm}.$ This requirement can be achieved by using hybrid suspended gate field effect transistors with an air gap height below 1 μm.