# Bimorph Lithium Niobate Piezoelectric Micromachined Ultrasonic Transducer

## TL;DR

This paper presents a novel bi-layer lithium niobate PMUT with high electromechanical coupling and displacement, demonstrating its potential as a compact, high-performance ultrasonic transducer platform.

## Contribution

It introduces a transferred periodically poled piezoelectric film on lithium niobate for efficient lateral excitation in PMUTs, with experimental validation of high performance.

## Key findings

- Operates near 1 MHz with 3.6% electromechanical coupling
- Achieves a peak displacement of 340 pm/V
- Demonstrates high figure of merit for sensing and transduction

## Abstract

This work demonstrates a prototype bi-layer piezoelectric micromachined ultrasonic transducer (PMUT) based on transferred periodically poled piezoelectric film (P3F) X-cut lithium niobate (LN). Opposite in-plane polarizations in the piezoelectric film stack are employed to enable efficient lateral field excitation of the flexural mode. Thanks to its high piezoelectric coefficient and low dielectric loss, the X-cut LN exhibits high figure of merits (FoMs) as both sensors and transducers. The fabricated PMUT demonstrates an out-of-plane mode near 1 MHz with an electromechanical coupling of 3.6\%. Laser Doppler vibrometry further validates the finite element analysis, showing a peak center displacement of 340 pm/V. These results establish bi-layer P3F LN PMUTs as a promising platform for compact and high-performance ultrasonic transducers. Future work will focus on theoretical analysis, modeling of the measured data, improving the design of the transducer topology, and mitigating feedthrough effects.