A Piezoelectric Micromachined Ultrasonic Transducer Using Thin-Film Lithium Niobate

This letter presents the first piezoelectric micromachined ultrasonic transducer (PMUT) based on thin-film lithium niobate (LiNbO
₃
). The figures of merit (FoMs) of LiNbO
₃
as ultrasound sensors and transducers are first studied, showing great prospective as a balanced transceiver platform. Efficient flexural mode excitation is achieved using a proposed lateral-field-excitation (LFE) structure. The implemented device shows a flexural mode at 7.6 MHz, with a high electromechanical coupling (k
²
) of 4.2%. Measured quality factor ( Q) in vacuum is 2605, indicating the low structural loss, while measured Q in air is 264, suggesting the ultrasound radiation. A dynamic displacement sensitivity of 20.2 nm/V is measured. Upon further optimizations, LiNbO
₃
-based PMUTs are promising candidates for miniature ultrasound applications.