Surface acoustic wave sensors to detect volatile gases by measuring output phase shift

Abstract

This paper presents properties of saw acoustic wave (SAW) gas sensors to detect volatile gases such as acetone, methanol, and ethanol by measuring phase shift. A dual-delay-line saw sensors with a center frequency of 100 MHz were fabricated on 128∘ Y-Z LiNbO3 piezoelectric substrate. In order to improve sensitivity of SAW sensors, a thin titanium (Ti) film as mass sensitive layer was deposited using e-beam evaporation on the surface of the SAW sensors. In our investigation the response time and sensitivity of SAW sensors were measured. The response time and sensitivity of SAW sensor with thin Ti film were strongly improved because of changing electrical and mechanical properties in the mass sensitive layer. As a result, high sensitivity and fast response time could be achieved by deposition of thin Ti film as mass sensitive layer on the surface of SAW sensor. It can be applied for high performance electronic nose system by assembling an array of different sensors.