FEM modeling SAW humidity sensor based on ZnO/IDTs/AlN/Si structures

In this study, we demonstrate a finite element method (FEM) simulation approach of surface acoustic wave (SAW) humidity sensors. The polycrystalline Zinc oxide (ZnO)/ Aluminum nitride (AlN)/Si-layered structure was simulated for SAW resonators and compared with experiment results. The humidity absorption behaviors of ZnO films coating on the propagation characteristics of the SAW were investigated by FEM modeling in the absence and presence of water vapor. The simulation frequency shift in different relative humidity (RH%) agreed with experiments values and gave a new approach to SAW sensor designing based on piezoelectric thin films.