Hydrogen effect on density and Young's modulus of thin films in acoustic sensors

This paper explains the sensing mechanism of acoustic hydrogen gas sensors based on Surface Acoustic Waves (SAWs). The main idea is to take advantage of the presence of two different modes of vibration to extract independently density and stiffness of the studied thin film. The adopted methodology is based on a parametric study determining the variation in the phase velocity of the sensitive layer according to thin film parameters. Then, the experimental extraction of this phase velocity allows the determination of the thin film experimental parameter values by using the established model. This new methodology allows the measuring of the density and Young's modulus of thin films in hydrogen atmosphere. Also, it improves the study of sensing mechanism in the thin films. Especially, since the analysis of the sensitive layer's properties within a gaseous atmosphere is not simple.