Sensitivity comparison between gas sensors using SAW and shear horizontal plate-mode oscillators

• Published in: Sensors and actuators. B, Chemical Chemical, 1992, Vol.6 (1), p.274-278
• Main Authors: Rebière, Dominique, Pistré, Jacques, Hoummady, Moussa, Hauden, Daniel, Cunin, Patrick, Planade, Roger
• Format: Article
• Language: English
• ISSN: 0925-4005; 1873-3077
• DOI: 10.1016/0925-4005(92)80069-A

Gas sensors using SAW oscillators are now well known. However, the corresponding devices based on shear horizontal (SH) plate-mode oscillators have not received so much attention. Although both of them work on a mass-loading effect due to adsorption properties of a chemical coating, SH plate-mode delay-line oscillators are considered to be more sensitive. Few results are available to support this assertion. Using computer simulation, the responses of the two sensor types are calculated and compared when their active chemical layer is the seat of gas-induced physical modifications. The simulation requires a knowledge of several physical constants for both materials (quartz and coating). The theoretical responses are expressed in terms of acoustic-wave phase velocity and calculated for different quartz crystal cuts by a perturbation method involving thickness, density and stiffness of the substrate and its coating. Used under the same conditions, the SH plate-mode device is found to be more sensitive than the SAW-mode one within a particular thickness domain.