In this study, we proposed an annular-shaped piezoelectric micromachined ultrasonic transducer (pMUT) based on a Pb(Zr,Ti)O₃-based monocrystalline thin film. This pMUT is expected to increase the resonance frequency while maintaining displacement sensitivity, making it superior to an island-shaped pMUT, which is a conventional design. To demonstrate the validity of this assumption, annular- and island-shaped pMUTs with a 60 μm-diameter diaphragm were prototyped and characterized. As a result, the annular-shaped pMUT exhibited a resonance frequency of 11.9 MHz, a static displacement sensitivity of 2.35 nm V⁻¹ and a transmitting figure-of-merit (FOM) of 28 nm MHz V⁻¹. On the other hand, the island-shaped pMUT exhibited a resonance frequency of 9.6 MHz and a static displacement of 2.5 nm V⁻¹ and an FOM of 24 nm MHz V⁻¹. Therefore, the annular-shaped pMUT was experimentally demonstrated to provide a higher FOM compared to the island-shaped pMUT. In addition, the annular-shaped pMUT with the optimal dimensions is found to be able to keep a relatively large fabrication margin. This is an advantageous point for the practical device fabrication. We believe this design has a potential to become a standard design for high-performance pMUT devices.

在这项研究中，我们提出了一种基于 Pb(Zr,Ti)O ₃基单晶薄膜的环形压电微机械超声换能器 (pMUT) 。该 pMUT 有望在保持位移灵敏度的同时提高共振频率，使其优于传统设计的岛形 pMUT。为了证明这一假设的有效性，对具有 60 μ m 直径隔膜的环形和岛形 pMUT 进行了原型设计和表征。结果，环形 pMUT 表现出 11.9 MHz 的共振频率、2.35 nm V ^-1的静态位移灵敏度和 28 nm MHz V ^-1的传输品质因数 (FOM). 另一方面，岛状pMUT表现出9.6 MHz的共振频率和2.5 nm V ^-1的静态位移和24 nm MHz V ^-1的FOM 。因此，实验证明环形 pMUT 与岛形 pMUT 相比可提供更高的 FOM。此外，发现具有最佳尺寸的环形 pMUT 能够保持相对较大的制造裕度。这是实际器件制造的一个有利点。我们相信这种设计有可能成为高性能 pMUT 设备的标准设计。