Investigation on electrode size of high frequency ultrasonic transducers

This paper presents a concept to increase the performance of high frequency ultrasonic transducers. For a sandwich high frequency ultrasonic transducer, the top electrode should be smaller than the piezoelectric plate to avoid shortcuts and edge effects. However, its size can influence properties of the transducer, and until now there is no research about it published. A theoretical investigation about influence of the top electrode size on properties of a transducer is conducted in this paper. First, two factors related with the top electrode size based on transmission coefficient and stored energy are proposed; Then, analysis on an Al-AlNAl on silicon wafers with different electrode sizes are performed and the results prove the effectiveness and the validity of the proposed factors. Finally, electrical impedance matching experiments are conducted to improve the properties of transducers with different electrode sizes, and the experiment results show that the improved resolution and sensitivity after matching.