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

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.

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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.

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