Surface Acoustic Wave (SAW) Gas Sensors

In recent years there has been a great interest in using surface acoustic wave (SAW) devices for the detection of both physical and chemical quantities. The SAWs in the field of sensors give rise to an interesting basic detecting technique since the mechanism of interaction between the acoustic propagation, which induces the sensor response, includes many different linear and non linear properties of the propagation medium related to mass density, elastic stiffness and, in piezoelectric materials, also to the electric and dielectric behaviour. In addition, as the acoustic energy is confined to a thin near-surface region of the substrate, SAWs are highly sensitive to surface perturbations of the propagation medium. The SAW based sensor must be seen as a complementary structure in respect to those based on other operating principles; for instance in MOS capacitors the capacitance, or on MOSFETs the drain current are …