A High-Performance PMUT Array Based on Bilayer Lithium Niobate

Abstract

This work demonstrates a linear PMUT array based on a bilayer X-cut lithium niobate (LiNbO3) structure. Leveraging LiNbO3's high piezoelectric coefficients and the bilayer's ability to harness the sign-changing in-plain strain associated to plate bending, the device achieves high transmit sensitivity (0.48 kPa/V at 10 mm), high current receive sensitivity (0.56 nA/Pa), high voltage receive sensitivity ($2.26 \mu ~\mathrm{V} / \text{Pa}$), and a low noise-equivalent pressure ($0.18 \text{mPa} / \sqrt{\text{Hz}}$). The array operates at 1 MHz with a fractional bandwidth of $82.5 \%(-6 ~\text{dB})$ and has an active area of $0.173 ~\text{mm}^{2}$. Figures of merit (FoMs) that capture the sensitivity-bandwidth-area trade-offs are reported and benchmarked with other PMUT technologies. The results position bilayer LiNbO3 as a promising route to compact, high-performance ultrasonic transducers.