Surface acoustic wave (SAW) NO/sub 2/ sensors: theoretical studies, measurements and design

The authors report on surface acoustic wave NO/sub 2/ sensors using quartz as the substrate and copper phthalocyanine (Cu-PC) as the chemical interface. The electronics of this self-contained device have been miniaturized and integrated in the measurement cell. The operating temperature is 90 degrees C and the quartz substrate cut was chosen so as to present its compensation point at this temperature. Theoretical studies of the devices are presented in terms of a multilayer model. The Lame constants of Cu-PC, necessary for the computation, were measured beforehand. The experimental technique involves the use of an automated measurement bench. Experiments made with the measurement bench at 350 MHz showed that the device sensitivity could easily be increased when working at higher frequency. The results obtained are compared to those already published.<>