Temperature stability of ZnO-based Love wave biosensor with SiO2 buffer layer

Theoretical calculations have been performed for the temperature coefficient of delay (TCD) of Love wave biosensor with c-axis oriented ZnO thin film layered structures on SiO2/Si substrate. The main interest of our paper is to optimize the SAW biosensor under the condition of temperature stability by considering the relations among electromechanical coupling coefficient, mass loading sensitivity and TCD. Some important results have been obtained by solving the coupled electromechanical field equations. It is found that the mass loading sensitivity can be further improved by adding a SiO2 thin film, and a zero TCD device also can be obtained after integrating with a proper thickness of SiO2 thin film. We try to obtain a device which possesses the mass loading sensitivity and coupling coefficient as high as possible and has zero TCD. The strategy of optimization is analyzed and a project is presented. We also find that though the interdigital transducers (IDTs) configurations and shorting metal arrangements influence the coupling coefficient a lot, they have few effects on TCD. This analysis is meaningful for the manufactures and applications of the ZnO/SiO2/Si structure Love wave biosensor.