Effect of humidity on SAW devices

[object Object] Adsorption of water vapors on single crystal and polycrystalline substrates is analized using the propagation of snrface acoustic waves as an experimental tool. The perturbation in the SAW velocity (AV/%), the number N of adsorbed species as well as the changes in the density Ap/p and in the elastic modulii AcJc, of the sorbent materails, are deduced in terms of the normalized SAW displacements A, Ay, A, and of the unperturbed SAW velocity v.. Vapour adsorption on polished plates of Pd:Ni is experimentally investigated. Results of the single crystal quartz and policrystalline films of Pd and measurements clearly show that humidity adsorption gives rise to effects whose amplitude is larger and whose time dnration is longer in the films then in the plates. These effects are also dependent on the orientation of the quartz, allowing to monitor the value and the rate of the effect by proper selection of a substrate materia