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A multi-layered surface acoustic wave (SAW) transducers have been employed for nitrogen dioxide gas sensing applications. The structure composes of a SiO2 guiding layer deposited on a 90° 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.
Date of Conference: 11-13 Dec. 2002