Our work, BROADBAND AND HIGH-PRESSURE OUTPUT PMUT ARRAY BASED ON LEAD-FREE KNN THIN FILM, is accepted by IEEE MEMS 2024.The first author of the paper is doctoral student Lei Zhao.

The abstract of this paper is as follows: 

High-performance lead-free piezoelectric ultrasound transducers have been highly desirable for applications in implantable, bio-compatible medical devices and environment-friendly consumer electronics. In this paper, we demonstrated design, fabrication, and characterization of lead-free (K, Na)NbO3 (KNN) based piezoelectric micromechanical ultrasonic transducer (PMUT) arrays with center frequency 4.7 MHz in liquid and 5.85 MHz in air. High-quality actuator type of KNN thin film was deposited via physical vapor deposition (PVD) and patterned using an optimized wet etching process with an oxide layer as a mask. Moreover, a -6dB fractional bandwidth of 95.7% is achieved via the optimization of layer stacks and acoustic impedance. A high transmitting sensitivity of 3.8 kPa/V @ 3 cm from one PMUT super-pixel (area 0.278 mm2 , 3×12 PMUTs) was obtained, which is comparable to previous PZT (lead-included) film based PMUTs.

Congratulations to Lei Zhao and the whole team for the achievement