Effects of electrodes on performances of multilayered film acoustic resonance biosensors

The multilayered film acoustic resonance biosensors operated in the thickness-shear mode, which can be utilized in liquid for biosensor applications. To obtain high sensitivity the biosensors operate at GHz, in which the thickness of the electrodes is comparable to that of the piezoelectric films, and their effects on the biosensors become important factors for performance optimizations of the biosensors. In the paper, a theoretical model of the biosensors fabricated by multilayered thin films in shear acoustic mode resonance is given. Based on the model, the performances, i.e., the resonant frequencies and quality factors, of the biosensors and the effects of the electrodes on the performances are systematically investigated. The calculated results demonstrate that for the electrodes with low acoustic impedance, the top electrode has dominant effect on the performances; for the electrodes with high acoustic impedance, the bottom electrode has dominant effect on the performances. These results show the effects of the electrodes on the performances, and provide methods for improving the accuracy and resolution of the sensors.