Analysis and impedance modeling of silica and polystyrene nanoparticles in EMIM structures for humidity sensing applications

This work shows the fabrication technology details and a proposed impedance spectroscopy modeling of Electrosprayed-nanoparticles Metal Insulator Metal (EMIM) structures, and their potential as humidity sensors. The impedance measurement of two structures based on 255-nm silica and 295-nm polystyrene nanoparticles under different relative humidity levels (30-90 %RH) and scanning electron microscopy were carried out. A higher capacitance in silica than in polystyrene EMIM structure is attributed to the adsorption of moisture and the diffusion of charges through the Grotthus mechanism onto the nanoparticle surface. The Poole-Frenkel dielectric conductivity in the silica capacitor is interpreted, which increases with decreasing humidity. While the Ohmic dielectric conductivity in PS nanostructure decreases with decreasing humidity. The silica EMIM structure has a good linear capacitance dependence on the humidity of almost 95% and a maximum sensitivity of 6362%, defined as ΔC/C30%, is obtained, making these devices a promising novel nanostructure for humidity sensing applications.