A Lithium Niobate Piezoelectric Micromachined Ultrasonic Transducer Operating in Thickness-Field-Excitation Mode With Enhanced Acoustic Emission

Lead-free piezoelectric materials have garnered increasing attention as environmentally friendly alternatives to lead-based transducers. Among them, lithium niobate (LN) is a promising candidate. However, the transmit displacement sensitivity of existing LN piezoelectric micromachined ultrasonic transducers (PMUTs) remains significantly lower than that of PZT devices due to the limitation of lateral-field-excitation (LFE). In this work, an LN PMUT operating in the thickness-field- excitation (TFE) mode was designed and fabricated on a 41° Y-cut lithium niobate on insulator (LNOI) substrate. The bottom electrode was innovatively fabricated by deep reactive ion etching and magnetron sputtering, which simplifies the fabrication process and reduces cost compared with conventional methods. The device achieves a transmit sensitivity of 460.3nm/V at an operating frequency of 400kHz, surpassing previously reported LFE LN PMUTs. [2025-0247]