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

这个FRG(重点研究小组)项目致力于材料科学和生物医学工程方面的研究，利用硅上的Pb(Mg1/3Nb2/3)-PbTiO3(PMN-PT)异质结构来研究新一代高性能的pMUT(压电微机械超声换能器)阵列，用于实时三维医学超声成像。其目标是与传统技术相比，实现更灵敏、更宽带宽、更便宜的换能器阵列。该方法是为了了解pMUT器件结构中外延压电薄膜的机电耦合现象，并直接在具有良好压电响应的硅上实现外延压电异质结构的制备。通过将PMN-PT薄膜与硅进行集成，可以利用成熟的器件制造工艺对硅进行图案化/微加工、大面积衬底的可用性以及与高性能电子电路的集成。研究活动包括：(1)用分子束外延技术直接在硅上生长SrRuO_3导电氧化物底电极；(2)用溅射法生长PMN-PT外延压电薄膜；(3)对PMN-PT薄膜的机电性能进行宏观和纳米尺度的表征；(4)利用高分辨率透射电子显微镜和分析电子显微镜对pMUT器件的微观结构和界面原子结构进行检测；(5)利用硅基外延PMN-PT异质结构设计和制备pMUT阵列；以及(6)使用杜克大学的实时超声扫描仪对用于医用超声成像的pMUT进行评估。所需的专业知识汇集在一个多学科团队中，成员包括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，通过使用复杂的研究工具以及跨学科的研究互动和方法，向研究生介绍现代、多学科的科学和技术。本科生还将参与实验室研究活动。此外，与高中生和科学教师的直接互动也是该项目的一部分。高中教师将参加威斯康星大学和阿贡国家实验室的暑期实验室研究体验。这一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.***