A layered SAW based NO/sub 2/ sensor with a copper phthalocyanine selective layer

A multi-layered surface acoustic wave (SAW) transducers have been employed for nitrogen dioxide gas sensing applications. The structure composes of a SiO/sub 2/ guiding layer deposited on a 90/spl deg/ rotated ST-cut quartz crystal substrate with a thin film of copper phthalocyanine acting as the selective layer. The dominant mode of acoustic propagation in the sensor is a combination of mainly a shear and a longitudinal displacement types. Such a structure has the advantage of confining the acoustic wave energy to the surface of the device, which increases the sensitivity of the system.