ScAlN film-based piezoelectric micromechanical ultrasonic transducers with dual-ring structure for distance sensing

Abstract

Piezoelectric micromechanical ultrasonic transducers (pMUTs) are a new type of distance sensors with great potential for applications in automotive, unmanned aerial vehicle, robotics, and smart-home. However, the previously reported pMUT is limited by short sensing distance due to lower output sound pressure. In this work, a pMUT with a special dual-ring structure based on scandium-doped aluminum nitride (ScAlN) is proposed. The combination of a dual-ring structure with pinned boundary conditions and a high piezoelectric performance ScAlN film allows the pMUT to achieve a large dynamic displacement of 2.87 μm/V and a high electromechanical coupling coefficient (k2t) of 8.92%. The results of the ranging experiments show that the proposed pMUT achieves a 6 m distance sensing, the farthest distance sensing up to date registered. This pMUT provides surprisingly fertile ground for various distance sensing applications.