Fabrication, modeling and simulation of high sensitivity capacitive humidity sensors based on ZnO nanorods

Recently, humidity sensors due to their broad applications in meteorology, health science, food science, and agriculture have been under extensive investigation. We report fabrication and characterization of high sensitivity capacitive humidity sensors based on ZnO nanorods. ZnO nanorods have been grown by means of chemical bath deposition. We have observed that by changing the seed layer thickness, nanorods with different aspect ratios and densities could be achieved. Furthermore, it is demonstrated that decreasing the density of nanorods has a positive effect on the response of the sensor. Moreover, an equivalent circuit model is proposed to explain the sensing mechanism. The devices were also simulated with COMSOL Multiphysics and a very good agreement with experimental data was observed. Finally a solution for increasing the sensitivity of the sensors is proposed.