Thermal sensitivity study of thin film over-layered SAW devices for sensor applications

Abstract

• Effect of temperature is studied on ST-X quartz-based SAW resonator with various thin films. • Polymer, metal oxides layers are coated over the device for further analysis. • The important finding is that metal oxide layer can be better option for thermal compensation over the device. • This study can be useful for fabrication of SAW based sensor for sensing applications. This paper presents the sensitivity study of ST-X quartz-based SAW sensor under the influence of temperature. SAW sensor based on ST-quartz structure with different non-conductive overlayers, including metal oxides (TiO2, ZnO) and polymers are used in the present work. Thermal study of SAW sensor with temperature compensated over-layer has been studied. In order to the study thermal behavior of SAW sensors, a shift in magnitude, centre frequency, phase, group delay, temperature coefficient of frequency (TCF) has been studied for temperature ranges 5 to 150 o C. The experimental results showed that uncoated/SAW sensors are more sensitive to temperature change but SAW sensor with overlayer shows less susceptible behavior to temperature change. TCF values for polymer/SAW, ZnO/SAW, and TiO2/SAW are -27.125 ppm/ o C, -21.67 ppm/ o C, -14.4 ppm/ o C respectively. The main outcome of this study is that an overlayer as temperature compensated layer will reduce the sensor's sensitivity but make sensor less susceptible to temperature changes and also improves sensor’s stability. This study will be useful for physical as well as chemical sensing applications.