Liu Tong, Yang Changhong, Si Jingxiang, Sun Wei, Su Daojian, Li Chenglong, Yuan Xiufang, Huang Shifeng, Cheng Xin, Cheng Zhenxiang
Shandong Provincial Key Laboratory of Preparation and Measurement of Building Materials, University of Jinan, Jinan, 250022, China.
Laoshan Laboratory, Qingdao, 266237, China.
Adv Mater. 2025 Feb;37(7):e2414711. doi: 10.1002/adma.202414711. Epub 2024 Dec 25.
Piezoelectric micromachined ultrasound transducers (pMUTs), especially those using lead-free materials, are crucial next-generation microdevices for precise actuation and sensing, driving advancements in medical, industrial, and environmental applications. Bismuth ferrite (BiFeO) is emerging as a promising lead-free piezoelectric material to replace Pb(Zr,Ti)O in pMUTs. Despite its potential, the integration of BiFeO thin films into pMUTs has been hindered by poling issues. Here, a BiFeO heterostructure compositionally downgraded with Gd doping is developed to introduce compressive strain, resulting in strong self-poling. Utilizing a large-area self-poled thin film over an entire 6-inch wafer, a pMUT with a 6 × 6 array at the device level is designed and evaluated. At a resonant frequency of 21 kHz, the dynamic vibration displacement can reach 24.0 nm. At 500 Hz, far below the resonant frequency of 21 kHz, the pMUT also displays sensitive converse piezoelectric response, even at a high temperature of 200 °C. This work represents a significant breakthrough in lead-free BiFeO thin film for practical sensing applications, paving the way for the transformation of macro-transducers into next-generation functional microdevices.
压电微机械超声换能器（pMUT），尤其是那些使用无铅材料的换能器，是用于精确驱动和传感的关键下一代微器件，推动了医学、工业和环境应用的发展。铋铁氧体（BiFeO₃）正在成为一种有前途的无铅压电材料，以取代pMUT中的锆钛酸铅（Pb(Zr,Ti)O₃）。尽管具有潜力，但BiFeO₃薄膜集成到pMUT中一直受到极化问题的阻碍。在此，开发了一种通过钆掺杂进行成分降级的BiFeO₃异质结构，以引入压缩应变，从而产生强自极化。利用整个6英寸晶圆上的大面积自极化薄膜，设计并评估了器件级具有6×6阵列的pMUT。在21 kHz的共振频率下，动态振动位移可达24.0 nm。在远低于21 kHz共振频率的500 Hz时，即使在200℃的高温下，pMUT也显示出灵敏的逆压电响应。这项工作代表了无铅BiFeO₃薄膜在实际传感应用中的重大突破，为将宏观换能器转变为下一代功能微器件铺平了道路。
