Use of surface acoustic waves for analysis of gases and surface processes induced by them

An analytical expression for the magnitude of the "response" of surface acoustic waves (SAWs) to gases is obtained. It is tested experimentally. The main features of the detection of gases by means of SAWs are predicted theoretically and confirmed experimentally. The SAWs in coated and uncoated gas sensors are compared. A technique for using SAWs to determine the relative changes in the density (Delta rho/rho) and the elastic moduli (dC(11)/C-11 and Delta C-44/C-44) Of films upon the adsorption (desorption) of gases is proposed. The possibility of using this technique to analyze adsorption and desorption processes is demonstrated. The adsorption properties of polycrystalline, thermally deposited palladium films before and after low-temperature vacuum annealing, as well as unannealed Pd and Pd:Ni films, are compared. The prospects of using SAWs to detect gases and to study surface processes induced by them are discussed. (C) 1998 American Institute of Physics. [S1063-7842(98)01402-0].