Propagation Characteristics of Surface Acoustic Wave and Properties of Gas Sensors on Quartz

The simulation of wave propagation in periodic piezoelectric surface acoustic wave (SAW) structures was reported in this study. Firstly, space harmonics method (SHM) was used to analyze Rayleigh SAW propagation under a periodic Al grating. The results of SAW propagation analysis were applied to design a two-port resonator with Al grating on ST-cut quartz. The measured frequency response of the two-port resonator was approximately similar to the simulation one. Then, the chemical interface of polyaniline/WO3 composites was coated on the SAW resonator for ammonia detection. The SAW sensor responded to the ammonia gas and could be recovered using dry nitrogen. Detecting to 9.3ppm ammonia, the frequency shift was 5.9ppm, the noise level was 0.18ppm, and a signal-to-noise ratio was 32.8.