FRG: Epitaxial Heterostructures of PMN-PT Piezoelectric / SrRuO3 Conductive Oxide for Medical Ultrasound Transducer Applications

这个FRG（重点研究小组）项目是杜克大学、密歇根大学、宾夕法尼亚州立大学和阿贡国家实验室的研究人员之间的合作成果，以及与波士顿科学公司、内声公司和朗讯技术公司的行业互动。该项目的目标是制造和表征单晶压电/导电氧化物异质结构的外延多层堆叠，并开发用于医学超声成像的新一代高频换能器阵列。薄层允许在更高的场中驱动堆叠，从而在不增加驱动电压的情况下利用高饱和应变。因此，换能器的整体重量和体积可以减少，更容易与其他设备集成。一个主要的挑战是在金属电极之间的单晶外延膜中材料的合成/加工，并有效地将它们集成到具有产量、均匀性、低表面粗糙度和与微电子技术相关的性能的压电器件中。具体研究方向包括：(1)单晶导电氧化物电极上压电材料单晶薄膜的合成、加工与表征；（2)利用高分辨透射电镜观察PMN-PT [Pb(Mg1/3Nb2/3)-PbTiO3）]薄膜的微观结构及PMN-PT/SrRuO3界面的原子结构和局部化学；(3)单活塞、100元阵列、192元多层阵列等单晶厚膜换能器的制备与表征；(4)压电换能器在医学超声成像中的应用与评价。高频换能器的工作范围从用于乳腺成像和心脏内扫描的10 MHz到用于血管内应用和眼科成像的40 MHz到用于超声显微镜的100 MHz。假设是，与传统技术相比，使用外延膜可以开发出更敏感、更宽带宽、更便宜的换能器，包括线性和多层阵列。该项目涉及材料科学和工程主题领域的基础研究问题，具有很高的潜在技术/医学相关性。该研究将为电子器件的重要材料合成和制造方面提供基础层面的新知识，并且从研究中获得的基础材料科学和工程知识和理解有望有助于提高用于生物医学应用的先进超声成像器件的性能。跨学科计划的一个重要特点是通过在一个基础和技术上重要的领域培养学生，将研究和教育结合起来。该FRG项目由两个工程项目（BES/BME、CTS/FPH）、一个MPS项目（DMR/EM）和MPS OMA（多学科活动办公室）共同支持

This FRG (Focused Research Group) project is a collaborative effort among researchers at Duke University, U. Michigan, Penn State U. and Argonne National Laboratory, as well as industry interactions with Boston Scientific, Endosonics, and Lucent Technologies. The objective of the project is the fabrication and characterization of epitaxial multilayer stacks of single crystal piezoelectric/ conductive oxide electrode heterostructures, and development of a new generation of high frequency transducer arrays for medical ultrasound imaging. Thin layers allow the stacks to be driven at higher fields thus taking advantage of the high saturation strain without increasing driving voltages. Thus, overall weight and volume of the transducer can be reduced and more easily integrated with other devices. A major challenge is in the synthesis/processing of materials in single crystal epitaxial films between metal electrodes, and to integrate them effectively for utilization in piezoelectric devices with advantages of yield, uniformity, low surface roughness, and performance associated with microelectronic technology. Specific research areas include: (1)synthesis, processing and characterization of single crystal films of piezoelectrics on single crystal conductive oxide electrodes; (2)examination of the microstructure in PMN-PT [Pb(Mg1/3Nb2/3)-PbTiO3)] thin films and atomic structure and local chemistry at PMN-PT/SrRuO3 interfaces using high resolution transmission electron microscopy; (3)fabrication and characterization of single crystal thick film transducers such as single pistons, 100 element arrays, and 192 element multilayer arrays; and (4)application and evaluation of the piezoelectric transducers for medical ultrasound imaging. High frequency transducers operate in the range from 10 MHz for breast imaging and intra-cardiac scanning to 40 MHz for intravascular applications and ophthalmic imaging to 100 MHz for ultrasound microscopy. The hypothesis is that more sensitive, broader bandwidth, less expensive transducers, including linear and multilayer arrays, can be developed using epitaxial films compared with conventional technologies.%%%The project addresses basic research issues in a topical area of materials science and engineering having high potential technological/medical relevance. The research will contribute new knowledge at a fundamental level to important materials synthesis and fabrication aspects of electronic devices, and the basic materials science and engineering knowledge and understanding gained from the research is expected to contribute to improving the perform-ance capabilities of advanced ultrasound imaging devices for biomedical applications. An important feature of the interdisciplinary program is the integration of research and education through the training of students in a fundamentally and technologically significant area. This FRG project is co-supported by two ENG programs(BES/BME; CTS/FPH), an MPS program(DMR/EM), and the MPS OMA(Office of Multidisciplinary Activities).***