Heterostructure-Based Surface Acoustic Wave Resonator for Gas Sensing

This paper proposes a heterogeneous structure-based surface acoustic wave resonator for gas sensing. The lithium niobate thin film based on a stacked heterogeneous structure is chosen as the piezoelectric layer, which has the advantage of suppressing energy leakage compared to conventional bulk crystals. A two-port resonator configured with sensing component polyisobutylene (PIB) film is designed for absorbing dichloromethane (DCM) in the atmosphere and coupling with the transverse acoustic wave. The two-dimensional analysis is performed to investigate the resonant frequency variation caused by gas absorption volume, using the multi-physics software COMSOL. Two types of resonators (with a 0.6 μm-thick PIB film or a 0.8 μm-thick PIB film) are designed for comparison. We also examined the performance of the sensor in atmospheres with different DCM concentrations (Concentration ranges from 10 % to 90 %, with a step of 10 %). Compared to the sensitivity of 2.51 kHz/100 ppm for the sensor equipped with 0.8 μm-thick PIB film, the sensor equipped with 0.6 μm-thick PIB film exhibits a higher sensitivity of 6.76 kHz/100 ppm.