New properties of the SAW gas sensing

Abstract

Novel attractive properties of SAW gas sensing are theoretically predicted and experimentally verified. It is demonstrated that the SAW response can be increased, decreased, reversed, cancelled, speeded up, aged down and selected without changing the sensitive layer, simply by properly selecting the acoustic substrate material and its crystallographic orientation. These new properties are shown to come from the elliptic polarization of the acoustic wave and from its dependence on the propagation conditions. An experimental verification of the theoretical predictions is carried out on SAW H/sub 2/ sensors using both Pd and Pd:Ni sensitive films, deposited on ATx-, STx- and yx-quartz substrates upon exposure to 1% H/sub 2/+N/sub 2/, 1% CO+N/sub 2/ and 1% N/sub 2/O+N/sub 2/ gas mixtures. These new peculiarities will make possible to develop a new generation of SAW sensors.