FRG: Piezoelectric Micromachined Transducers using Epitaxial PMN-PT Films on Silicon for Medical Ultrasound

该FRG（重点研究小组）项目解决了新一代高性能pMUT（压电微机械超声换能器）阵列研究中的材料科学和生物医学工程问题，该阵列使用硅上的Pb（Mg 1/3 Nb 2/3）-PbTiO 3（PMN-PT）异质结构进行实时3-D医学超声成像。与传统技术相比，其目标是更灵敏、更宽带宽、更便宜的换能器阵列。该方法是获得的机电耦合的现象，在pMUT器件结构中的外延压电薄膜的理解，并实现直接在硅上的外延压电异质结构制造具有上级压电响应。通过将PMN-PT膜与硅集成，使用了用于硅的图案化/微机械加工、大面积衬底的可用性以及与高性能电子电路的集成的成熟的器件制造工艺。研究活动包括：（1）利用分子束外延技术直接在硅衬底上生长SrRuO_3导电氧化物下电极，（2）利用溅射技术生长PMN-PT压电薄膜，（3）对PMN-PT压电薄膜的机电性能进行宏观和纳米尺度的表征，（4）对PMN-PT压电薄膜的电学性能进行了研究。（四）使用高分辨率透射电子显微镜和分析电子显微镜检查pMUT器件的微观结构和界面原子结构，通过聚焦离子束蚀刻限定的位置;（5）使用硅上的外延PMN-PT异质结构设计和制造pMUT阵列;和（6）使用杜克大学实时超声扫描仪评估用于医学超声成像的pMUT。所需的专业知识汇集在一个多学科团队中，成员从事材料科学和生物医学工程。教育和推广工作被整合到研究计划中，通过使用先进的研究仪器，以及跨学科的研究互动和方法，向研究生介绍现代多学科科学和技术。本科生也将参与实验室研究活动。此外，与高中学生和科学教师的直接互动是该项目的一部分。高中教师将参加一个夏季实验室的研究经验，在美国。威斯康星州和阿贡国家实验室。这种研究经验将与现有的课程开发计划相协调，以便将其纳入高中课程。该项目由MPS/DMR/EM和ENG/BES/BME-RAPD方案共同支持。

This FRG (focused research group) project addresses materials science and biomedical engineering issues in research on new generation, high performance pMUT (piezoelectric micromachined ultrasound transducer) arrays using Pb(Mg1/3Nb2/3)-PbTiO3 (PMN-PT) heterostructures on silicon for real-time 3-D medical ultrasound imaging. The aim is for more sensitive, broader bandwidth, less expensive transducer arrays compared with conventional technologies. The approach is to gain understanding of phenomena governing electromechanical coupling in epitaxial piezoelectric films in pMUT device structures, and to achieve epitaxial piezoelectric heterostructure fabrication directly on silicon with superior piezoelectric response. By integrating PMN-PT films with silicon, use is made of well-developed device fabrication processes for patterning/micromachining of silicon, the availability of large-area substrates, and integration with high performance electronic circuits. Research activities include: (1) growth of epitaxial SrRuO3 conductive oxide bottom electrodes directly on silicon by MBE; (2) growth of epitaxial piezoelectric PMN-PT films by sputtering; (3) macroscale and nanoscale characterization of the electromechanical properties of PMN-PT films; (4) examination of the microstructure and interface atomic structure of pMUT devices using high resolution transmission electron microscopy and analytical electron microscopy at locations defined by focused ion beam etching; (5) design and fabrication of pMUT arrays using epitaxial PMN-PT heterostructures on silicon; and (6) evaluation of the pMUT for medical ultrasound imaging using the Duke University real-time ultrasound scanner. The required expertise is assembled in a multidisciplinary team with members working in materials science and biomedical engineering. %%% Education and outreach efforts are integrated into the research program, introducing graduate students to modern, multidisciplinary science and technology through use of sophisticated research instrumentation, and research interactions and approaches across disciplines. Undergraduate students will also be involved with laboratory research activities. Additionally, direct interaction with high school students and science teachers is a part of the project. High school teachers will participate in a summer laboratory research experience at U. Wisconsin and Argonne National Laboratory. This research experience will be coordinated with an existing curriculum-development program, in order to integrate it into the high-school curriculum. The project is co-supported by the MPS/DMR/EM and ENG/BES/BME-RAPD Programs.***