Simulation of a one Port Saw Resonator with Trenches Containing Palladium for Sensing Hydrogen

A Surface Acoustic Wave (SAW) resonator consists of a piezoelectric substrate over which comb-shaped metallic electrodes called as interdigital transducer (IDT) are fabricated. The paper presents simulation of a one port SAW resonator with trenches between IDT electrodes to hold Palladium (Pd) for sensing hydrogen (H₂) gas. The dimensions of trenches are optimized. Pd is deposited in the trenches as a sensing medium due to its high affinity to H₂. The absorption of H₂ in the Pd changes its material properties such as Young's modulus and density, and changes the velocity of SAW causing change in resonance frequency of the SAW resonator. Simulation uses finite element method in COMSOL Multiphysics. The changes in Young's modulus and density of Pd at different H₂ concentrations are used in the simulation, and it is observed that the resonance frequency of the resonator reduces as the H₂ concentration in Pd increases. The frequency shift in the range of a few kHz for a 340.2 MHz resonator is noticed. The results of resonance frequency shift versus concentration of H₂ in Pd are plotted.