Xiaoqing Pan - US grants

9704175 Martin This award provides support for the acquisition of a Gatan Imaging Filter (GIF) accessory for the JEOL 4000 EX High Resolution Transmission Electron Microscope (HREM) located in the University of Michigan Electron Microbeam Analysis Laboratory (EMAL). The GIF consists of a curved magnetic sector lens that acts as a prism to disperse the transmitted electron beam as a function of energy. The dispersed beam can then be filtered to create images or diffraction patterns from selected portions of the electron energy loss spectra. This instrument would significantly enhance the microanalytical capabilities of the electron optics instrumentation at EMAL. Additional functionality provided by the GIF which is not presently available includes: (1) high resolution elemental and electronic state mapping of low atomic number elements, (2) improved contrast of polymer and organic thin films on substrates, (3) improved electron diffraction analysis by removal of inelastically scattered radiation, and (4) improved contrast in convergent beam electron diffraction patterns. Research underway in our laboratory which wi11 directly benefit from this acquisition includes the construction and characterization of grain boundary defects in optoelectronically active ordered polymers; the synthesis, and processing and characterization of thermally reactive benzocyclobutene functionalized polymers; the processing and microstructure of genetically engineered polypeptides for biocompatibility of micromachined silicon sensors for neural prosthetics, and the microstructure of polymers and polymer composites near surfaces. The instrument will also provide useful capabilities for other research projects in Materials Science and Engineering, Chemical Engineering, and Nuclear Engineering and Radiological Sciences departments, as detailed in the text of the proposal. %%% The GIF will provide an enhancement of the electron optics facility at EMAL, directly influencing the re search opportunities available for students, staff, and faculty who use these instruments. It will also be used in the curriculum as part of the laboratory sessions for graduate and undergraduate courses in Microstructure of Materials (MSE 460, MSE 560, and MSE 662). The GIF will also be used in summer short courses on Polymer Microscopy offered through the University of Michigan Continuing Engineering Education program. ***

9871177
Mansfield
Analytical electron microscopy (AEM) is critical to the characterization of metals, ceramics semiconductors, nano-composites, catalysts and geological materials. This Major Research Instrumentation proposal seeks support from NSF for the acquisition of a field emission gun analytical electron microscope (FEG-AEM). This instrument would become the primary analytical electron microscope for materials research, replacing the existing AEMs in the University of Michigan's Electron Microbeam Analysis Laboratory (EMAL). The new FEG-AEM will offer nearly two orders of magnitude higher electron beam current and a factor of three smaller electron probe than the existing instrument. This increase in beam current will mean that analyses may be performed on the nanometer length scale. The new microscope will be located in one of the custom -designed laboratories consisting of 360 square feet of temperature-controlled, low-vibration and low-field space.
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The new FEG-AEM, to be acquired under the National Science Foundation's Major Research Instrumentation program, will be the primary focus of a wide variety of materials research programs across a wide range of science and engineering disciplines. The active departments include: Materials Science & Engineering, Nuclear Engineering and Radiological Sciences, Chemical Engineering, Electrical Engineering & Computer Science, Applied Physics and Geological Sciences. Over 22 research projects, funded at a total level of over $5M, with 19 faculty, 29 graduate student researchers, and 5 undergraduate students, will be directly impacted by the new FEG-AEM. The new instrument will provide essential capabilities to the University's research programs, attract new research programs and allow the training of graduate students in advanced analytical electron microscopy.
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9875405
Pan

The research and development of reliable chemical sensors parallels the demand for a high degree of control over air pollution and fuel combustion efficiency for a variety of combustion processes, and increasing concern over safety in homes and in industrial activities involving flammable and poisonous gases. One of the main obstacles in the development of sensitive, selective and durable gas sensors has been the lack of adequate understanding of the fundamental processes involved in the operation of these devices and the relationships between these processes and the microstructure and composition of the sensing materials. This Faculty Early CAREER Development project will focus on nanocrystalline tin oxide materials, a model system for use as chemical sensors, to obtain fundamental understanding of the structure-property relationships. Systematic experiments are planned to investigate: (1) microstructural instabilities and crystal defect (e.g., crystallographic shear planes, grain boundaries, and dopants) evolution during the reaction process in the gaseous environment at elevated temperatures; (2) the atomic structure and electronic characteristics of individual defects (crystallographic shear planes, twin boundaries, and special grain boundaries) and interfaces; (3) correlation of microstructure, morphology, and chemical composition information with electrical measurements in different gaseous atmospheres at elevated temperatures. The studies on nanocrystalline tin oxide films will be conducted by spatially resolved microscopy and spectroscopy techniques in combination with impedance measurements within various simulated gaseous environments. Specifically, such advanced microscopy techniques will be combined with the thermal and chemical pre-treatment of specimens using a specially designed apparatus which simulates the environment the gas sensors encounter in use. Through the course of the research project the PI plans to explore the commercial software simulation programs for use in students education and training in crystal physics. In addition, a virtual microscopy database will be established, accessible via the Web, for images, renderings of crystal structures, and video clips/segments demonstrating the in-situ electron microscope observations.


One of the main obstacles in the development of sensitive, selective and durable gas sensors has been the lack of adequate understanding of the fundamental processes involved in the operation of these devices and the relationships between these processes and the microstructure and composition of the sensing materials. The results from this Faculty Early CAREER Development project about the structure and chemistry of tin oxide, a model gas sensing material, will be used to interpret the electrical properties and sensing performance of that material and will provide guidance on how to tailor solid state chemical sensors, which have optimized microstructure and desirable sensing properties. The proposed research involves the utilization and development of a number of advanced tools, such as image simulations, structural modeling, and electron microscopy. The long-term goal of the educational plan is to develop non-traditional and innovative pedagogical techniques that will provide graduates with the intellectual, creative, and scientific understanding needed to prosper in the modern scientific and engineering fields. These approaches are aimed to ensure that the students are adequately prepared for the scientific and industrial environment of the future.

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.
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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).
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0103354
Schlom

The technical objective of our NIRT is to understand the fundamental science underlying the structural, dielectric, and optical response of artificially-engineered nanoscale ferroelectrics, which can be drastically different from that of conventional homogeneous ferroelectrics. Using "first-principles effective Hamiltonian" approaches (based on lattice Wannier functions) and Landau-Ginzburg-type phenomenological methods, we will predict the effect of one-dimensional composition and strain gradients, and mechanical and electrical boundary conditions on the appearance and stability of the spontaneous polarization in these systems and on the modifications of ferroelectric domain structures. These predictions will be compared against observations on corresponding nanostructures (made by reactive MBE) of perovskite ferroelectrics in which composition and strain are varied in one direction. The resulting films will be characterized via a combination of TEM, x-ray diffraction (including synchrotron studies), Raman spectroscopy, second harmonic generation, dielectric property measurements as a function of electric field and temperature, and piezoelectric and pyroelectric techniques and compared with corresponding theoretical predictions in order to refine our understanding of nanoscale ferroelectrics. Composition and strain gradients in ferroelectric films will be investigated as a means to incorporate new functionalities: enhanced dielectric and pyroelectric responses, as well as a variety of novel optical properties.
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For over 30 years molecular beam epitaxy (MBE) has been used to build up layered semiconductor nanostructures atom-by-atom to investigate and improve our understanding of semiconductor physics and create new devices. These devices (which include laser diodes, high-performance transistors, and magnetic field sensors) have advanced healthcare, national security, communications, entertainment, and transportation-resulting in significant improvements in the quality of life for all Americans. Recent progress in research has demonstrated that this same atom-by-atom synthesis technique can be used to build up nanostructures of oxides, including ferroelectrics, with comparable nanometer-scale layering control. Since ferroelectric materials exhibit a wide variety of electrical, optical, and electromechanical properties, they are extensively used in healthcare (e.g., medical ultrasound), national defense (e.g., night vision and sonar systems), and communications (e.g., miniature capacitors for cell phones and computers). The ability to customize the layering of ferroelectric materials at the atomic-layer level opens exciting possibilities in terms of creating new functional materials that we believe can be designed (with sufficient understanding) to have exceptional properties. The improved understanding gained via this research will be applied to the development of improved (enhanced performance and smaller size) capacitors, night vision devices, and optical components. This NIRT program will also train and educate future scientists in a highly interdisciplinary research environment in a technologically-significant area of national importance.

This proposal was submitted in response to the solicitation "Nanoscale Science and Engineering" (NSF 00-119). The award is jointly supported through outside sources and the NSF Ceramics and Electronic Materials programs of the Division of Materials Research in MPS with the assistance of the initiative.

0210449
Eom

This proposal was received in response to the Nanoscale Science and Engineering Initiative, Program Solicitation NSF 01-157, in the NIRT category. The proposal focuses on understanding intrinsic phenomena governing spin transport at the nanoscale, and the development of new methods for its manipulation for future spin-controlled, magneto-electronic, devices. It addresses one of the most exciting aspects of current research on next-generation electronic devices: the manipulation of spin, rather than only electrical charge. The advantages of these magnetoelectronic devices include nonvolatility, faster switching in static memory elements, and higher density due to a simpler device structure. These issues become even more important as technology drives device sizes toward the nanoscale, where new fundamental physical effects emerge that alter spin transport, as well as high-frequency dynamics and switching times.
An understanding of these issues at the nanoscale requires single-crystal magnetic heterostructures with atomically-sharp interfaces, patterned to nanometer dimensions. This proposal probes nanoscale spin transport phenomena in epitaxial magnetic oxide nanostructures grown with atomic-layer control, whose magnetic, electronic, and interfacial properties are tuned at will. Layers with defined electronic, magnetic, and morphological characteristics positioned with atomic-layer control in epitaxial systems are used to address crucial fundamental questions in magnetic nanostructures.
This research program consists of 1) design, growth, and characterization of epitaxial magnetic oxide heterostructures with atomic layer control by pulsed laser deposition with in-situ real-time structural analysis 2) high-resolution and analytical TEM to determine atomic structure and electronic properties of the interfaces; 3) nanoscale patterning of novel magnetic heterostructures below 50 nm; 4) scanning probe measurements of topography and local electronic properties; 5) education and outreach efforts with a focus on introducing young people to modern, multidisciplinary science and technology, using the research direction as a vehicle.
The multidisciplinary, multiuniversity/industry team consists of members working in Materials Science, Physics, Electrical Engineering, and device development. Research, education, and outreach all follow the theme of nanoscale structures, novel phenomena, and spin transport control. This work will build a scientific foundation for the understanding of new phenomena in nanoscale spin-controlled devices. The PIs industrial and multidisciplinary interactions will be very beneficial in advancing research as well as in educating students. This study will also provide fundamental guidelines in the atomic-scale control of nanoscale systems such as ferroelectrics and oxide-semiconductor integration that are important for next-generation technology.

Objectives of this project are: (1) to expand basic knowledge of growth and property characterization of high-quality oxide semiconductor thin films and p-n heterostructures; (2) to systematically characterize electrical transport properties of the films and p-n heterostructures as a function of chemical doping, film thickness, bias applied, and temperature; (3) to fabricate model systems based on epitaxial single crystal films consisting of field effect transistor (FET) structures and develop a fundamental understanding of the effect of bias applied across the p-n junction on electrical transport properties and selective adsorption properties; and (4) to explore fabrication and characterization of more complex devices such as bipolar transistors with an exposed p-n junction. These devices offer the possibility of amplified electronic response to adsorption at exposed p-n junctions, which may provide a new level of control at the atomic and molecular level.
The long-term goal is to develop a fundamental understanding of oxide-based semiconductor heterostructures suitable for the design of nanoengineered sorbents, tunable displays, catalytic materials, and chemical sensors. The understanding gained is expected to provide guidance for improvement of chemical selectivity and sensitivity, and provide a science base for the development of microelectronic devices for selective, tunable chemical sensing. The insights gained will be beneficial not only for advancing chemical sensor technology and for improving health and safety in society, but also impact the basic research and technology development of transparent electrodes for electronic and optical devices. Additionally, through collaboration with Ford, fundamental information that this project will provide may improve emissions control technology for lean-combustion engines. Thus, the intellectual and broader impact of the proposed research may reach well beyond the realm of chemical sensing.
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This project addresses basic materials research issues in a topical area of materials science with technological relevance, and places emphasis on the integration of research and education. The research program provides excellent opportunities for hands-on experience in the use of sophisticated scientific equipment. Graduate and undergraduate students will be involved in the synthesis, processing, and characterization of electronic materials. The project integrates research with educational outreach which includes (1) creating a mechanism to expose materials research to high school minority students through the existing NASA SHARP Plus program at the University of Michigan, (2) involving undergraduates (particularly women and minority students) in research early in their careers, and (3) bringing the nano-world to the classroom through remote control of electron microscopes via the internet. It is planned to use this facility to demonstrate to a high school class, both live and via a virtual microscopy base, how materials can be manipulated at the atomic scale, and also to use this system for demonstrations to attract undergraduates to materials science and engineering. Students involved in this project will have the opportunity to learn film growth techniques, device fabrication, materials characterization, and to interact with high school students. This interdisciplinary education will provide students with special opportunities and a broad perspective valued in both industrial and academic research.
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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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NON-TECHNICAL DESCRIPTION: For many years molecular beam epitaxy (MBE) has been used to build layered semiconductor nanostructures atom-by-atom to investigate and improve our understanding of semiconductor physics and create new devices. These devices (which include laser diodes, high-performance transistors, and magnetic field sensors) have advanced healthcare, national security, communications, entertainment, and transportation-resulting in significant improvements in the quality of life for all Americans. Recent progress in research has demonstrated that this same atom-by-atom synthesis technique can be used to build nanostructures of oxides, including ferroelectrics, with comparable nanometer-scale layering control. Since ferroelectric materials exhibit a wide variety of electrical, optical, and electromechanical properties, they are extensively used in healthcare (e.g., medical ultrasound), national defense (e.g., night vision and sonar systems), and communications (e.g., miniature capacitors for cell phones and computers). The ability to customize the layering of ferroelectric materials at the atomic-layer level and strain them opens exciting possibilities to dramatically enhance their properties. The improved understanding gained via this research will be applied to the development of improved optical and acoustic devices. Future scientists in a highly interdisciplinary research environment in a technologically significant area of national importance will be trained and educated within this program. Professors from Pennsylvania State University, University of Wisconsin, University of Michigan and Rutgers University will run hands-on workshops during the summers at each of the campuses involved in this research team to expose K-12 students to the thrill of science.

TECHNICAL DETAILS: The technical objective is to understand the fundamental science underlying the electric, magnetic, and optical responses of strained nanoscale ferroelectrics and multiferroics. An integrated theoretical and experimental effort will be taken. Specifically, "first-principles effective Hamiltonian" approaches based on lattice Wannier functions and Landau-Ginzburg type phenomenological methods will be used to identify ferroelectric and multiferroic materials and heterostructures in which large enhancements in properties are expected with strain. Films will be grown by MBE and laser-MBE, patterned by focused ion beams, and characterized using a combination of x ray diffraction, analytical and transmission electron microscopy, Raman spectroscopy, second harmonic generation, and ferroelectric measurements, all as a function of temperature. Strain is utilized in many semiconductor device structures to improve the transport properties of thin semiconductor layers. Within this project, it will be used to enhance the properties of ferroelectrics. Ferroelectrics are very sensitive to strain and a distinct advantage of thin ferroelectric materials over their bulk counterparts is that they may be strained well beyond where their bulk counterparts would crack. For nanoscale ferroelectrics, huge strains become accessible. This feature combined with the ability to precisely integrate and engineer oxides at the atomic level provides a means to investigate, develop, and exploit the properties of oxides for optical modulators, two-dimensional photonic bandgap structures, and phonon-confining piezoelectric structures relevant to the long-term realization of a phonon laser.

Technical

This program funds a new advanced, spherical aberration-corrected high-resolution transmission electron microscope, which will be situated in the University of Michigan North Campus Electron Microbeam Analysis Laboratory. The instrument will have a resolution of 0.8 angstroms in the scanning transmission mode. It will enable researchers to determine chemistry, atomic structure, bonding characteristics, and three-dimensional imaging of materials at the true atomic level. Although it will be a critical instrument in the support of the wide range of nano-technology and energy research programs at the university, it will also operate as a resource for research institutions, both in industry and academia, in southeastern Michigan and the surrounding states. The instrument will have a 300 kV monochromated field emission gun and will have spherical aberration correction of the probe forming system. The imaging system will allow both scanning imaging and static beam imaging. In scanning imaging with a high angle annual dark field detector this microscope will allow atomic resolution imaging with atomic number contrast. Chemical analysis will be conducted by high-resolution electron energy loss spectroscopy, convergent beam electron diffraction and energy dispersive X-ray spectrometry.


Non-Technical

This program funds a new high resolution transmission electron microscope, an instrument that images extremely fine structure of material and is critical to successful nanotechnology and energy research in the University of Michigan and other research institutions in southeastern Michigan. In lieu of light, the transmission electron microscope uses a very high energy beam of electrons (300,000 volts) to probe the thin foils or particles of materials. The samples are so thin that 250 of them would be required to match the thickness of the average human hair. The imaging resolution of the new microscope will be higher than any previously located in Michigan. It will, for example, be able to image individual impurity atoms in the atomic lattices of silicon devices. The instrument will also be capable of performing chemical analyses of these samples, using what are known as spectroscopic techniques. Spectroscopy involves measuring the energy range of electrons or X-rays emitted by the sample when the high energy electron beam interacts with it. The instrument will allow researchers in the region to compete globally in research in nanotechnology, energy related materials and biological technologies. It will mean that research requiring materials characterization in Michigan will remain at the leading edge.

"This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5)."
Technical. The goal of this focused research group (FRG) proposal is to achieve an atomic-level understanding of the growth and novel properties of switchable oxide hetero-interfaces, with advanced properties and new functionalities. The idea is to create new 2D interfacial materials, switched by external stimuli, whose electronic, magnetic, optical, and transport properties depend critically on atomic-scale materials characteristics. Switchable interface materials with, spatially modulated conductance, tunable by an applied electric field, and spin-polarized interface materials responding to magnetic fields will be explored. The focus is on identification and understanding of atomic level mechanisms and electrical transport associated with atomic layer-by-layer synthesis. It is anticipated that functionalizing 2DEGs at oxide interfaces may be transformative, in that it could lead to new research fields where interplay between ferroelectricity and 2D transport reveals unexplored properties important for device applications. Logic devices with switchable electron and/or spin current based on 2D interface materials are envisioned. The approach involves a collaborative coordinated effort to explore materials science issues of growth and novel properties of switchable oxide hetero-interfaces. Specific tasks are (1) theoretical exploration of the dependence of interfacial properties on materials characteristics; (2) atomic layer epitaxial growth and characterization of switchable two-dimensional oxide hetero-interface materials; (3) electrical transport and magnetic characterization of interfacial electronic properties.
Non-Technical. The project addresses fundamental research issues in a topical area of electronic/photonic materials science having technological relevance. This research is expected to identify and resolve fundamental materials science issues in switchable 2D interfacial oxide heterostructures; prototype electronic devices fabricated from these interfacial materials may find new and wide-ranging applications. Education and outreach activities will be integrated with the research. The education goal is to provide a broad interdisciplinary experience for all students. This includes first-year student rotation through research groups, working in an international institution and the Argonne National Laboratory, research interactions with individuals of diverse backgrounds, and participating in outreach programs. Students from underrepresented groups will be actively recruited through collaboration with U. Puerto Rico-Mayagüez. Secondary school teachers will come from Puerto Rico to the U. WI for a nanoscience learning/research experience. They will develop classroom material, and put in place programs for implementation at their schools in Puerto Rico. Graduate students will be involved as mentors to the teachers. The results of the program will be widely disseminated through teacher presentations at schools and at education conferences, and through published articles.

0933239
Thompson

Early transition metal (Group IV-VI) carbides and nitrides are a fascinating class of materials with a broad range of potential applications including use as catalysts for energy and environmentally sustainable processes. These relatively low cost materials can be produced in nanoscale form with surface areas as high as 200 m2/gr, have been demonstrated to be active for a number of industrially significant reactions including water gas shift and alkane isomerization, and are thermally and chemically stable. The design of nanoscale early transition metal carbide- and nitride-based catalysts would benefit significantly from a better understanding of relationships between their structural, compositional and functional properties.

The goal of this research is to elucidate key structural and compositional features that govern the catalytic properties of early transition metal carbides and nitrides using two commercially relevant test reactions, the water gas shift (WGS) and Fischer-Tropsch Synthesis (FTS). The principal techniques that will be employed to accomplish the project goal are ultrahigh resolution transmission electron microscopy (TEM) and in situ x-ray absorption spectroscopy (XAS). The TEM and XAS results will be complemented by results from infrared spectroscopy and x-ray photoelectron spectroscopy.

This effort is responsive to the Catalysis and Biocatalysis Program goal of supporting multidisciplinary research on the synthesis and characterization of catalysts that function at the nanoscale. Potential applications for nanoscale carbide- and nitride-based catalysts include the production of hydrogen and "green gasoline" via FTS, and consequently the project supports efforts related to energy diversity and reductions in greenhouse gas emissions.

The intellectual merit of the proposed research lies in a significant expansion of the knowledge base for early transition metal carbide and nitride catalysts. While the database of reactions catalyzed by these materials has grown, there is little fundamental information about relationships between their structure, composition and function. The ultrahigh resolution TEM will allow, perhaps for the first time, high resolution imaging of the non-metal atoms in the metal atom matrix of the catalyst. In addition, XAS, one of only a few in situ methods, will provide the type of compositional, structural and electronic information needed to develop unambiguous correlations. Relationships derived during the proposed research will significantly enhance our fundamental understanding of the character of carbides and nitrides, and could facilitate their design and development as catalysts and catalyst supports for the sustainable production of a variety of chemicals and fuels.

With regard to the broader impacts, the proposed research will engage under-represented minority high school, undergraduate and graduate students in socially relevant research. The proposed project will leverage on-going education and outreach activities including the Michigan-Louis Stokes Alliance for Minority Participation and Undergraduate Research Opportunity Program. Through an expansion of the University of Michigan Chemical Sciences at the Interface of Education (CSIE) program, undergraduate and post-doctoral chemical engineering and materials science students will be able to add education to their professional studies. In addition, through a collaboration with the IDEA Institute, teachers from the Detroit and Ypsilanti School Districts, both of which have large populations of underserved students, will be engaged in summer camp programs focused on microscopy and surface science. Researchers engaged in the proposed project have long-standing commitments to increasing the participation of underrepresented groups in authentic research and integrating research into educational activities.

Technical. This project addresses structure, composition, chemical bonding, and electronic properties of defects (dislocations and dopants), film/substrate interfaces, and p-n junctions in un-doped and doped ZnO films. Specific tasks are: (1) growth and characterization of ZnO thin films with different types of dopants and p-n junctions; (2) atomic-scale characterization of structure and electronic properties of interfaces; (3) in situ study of the stability and response of crystal defects and interfaces to applied electric field using an STM/TEM holder for TEM/STEM in combination with HRTEM and EELS. The crystal defects and interfaces to be studied include dopants, dislocations, grain boundaries, film/substrate interfaces, and p-n junctions. A TEM with spherical aberration-corrected cold field emission gun will be utilized for these studies; it provides sub-Å resolution for imaging and a very bright electron probe with an energy spread of 0.3 eV for electron energy-loss spectroscopy. Extensive characterization of the atomic structure and nanoscale electronic properties of defects and interfaces will be emphasized. Understanding based on these results is expected to allow subsequent development of p-type ZnO material, desirable for electronic and optical devices--detectors, light-emitters, transparent thin FETs or spin-based devices.
Non-Technical. The project addresses fundamental research issues in a topical area of electronic/photonic materials science having technological relevance. The project includes multifac-eted educational opportunities for students. Undergraduates will be incorporated into this re-search via senior theses and REU experiences. Both graduate and undergraduate students will become involved in multiple steps of the solution of interdisciplinary research objectives. The PI will run hands-on workshops (Microscopic World of Materials) each summer for gifted female and minority K-12 students at the University of Michigan through NASA's Summer High School Apprenticeship Research Program. This interdisciplinary education will provide students with a unique perspective expected to be helpful toward furthering their interest in industry and academic research.

Abstract

#1159240
Pan, Xiaoqing

Gradual coarsening of the catalytically-active metal particles in a catalyst is one of the fundamental reasons for loss of activity over time. For three-way automotive exhaust-gas catalysts, a recent phenomenon, the redox-induced cyclical re-dispersion of the metal in novel precious-metal-doped-perovskite formulations has been proposed as a possible means of reducing this problem. Recent work showing that this phenomenon occurs over distances of only a few nanometers in these systems suggests that a practical perovskite-based catalyst will likely involve ultra-thin perovskite films or coatings. In an effort to assess the viability of such a catalyst, this GOALI award covers a carefully designed combination of electron microscopy and catalytic measurements on model planar and high-surface-area powder catalysts to be conducted at University of Michigan and Ford Research and Innovation Center under the supervision of Profs. Xiaoqing Pan and George Graham and of Dr. Robert McCabe, respectively. Specific objectives include the observation of self-stabilizing or self-regenerative catalyst behavior in ultra-thin perovskite films on planar supports, the production of perovskite-coated high-surface-area powders, the measurement of kinetics and detailed chemical potential dependence of structural transformations in model powder catalyst systems, the catalytic characterization of perovskite-based precious-metal catalysts using simple reactions to probe three-way catalytic activity, and ultimately the durability assessment of perovskite-based precious-metal powder catalysts under realistic conditions. An important aspect of the structure-property relationship testing will be to clearly assign catalytic activity to either supported metal particles or metal-doped perovskite.

Broader Significance and Importance:

Automotive exhaust-gas catalysts currently account for 30-50% of the world-wide demand for Pt and Pd, and the corresponding demand for Rh is even higher, ~80%. Since the utilization of these metals in this application has historically never exceeded a few percent by end of life, due primarily to particle coarsening, the attainment of even a modest increase in efficiency would be of tremendous significance, both commercially as well as scientifically. The proposed work affords the opportunity for graduate and undergraduate students at University of Michigan to collaborate closely with catalyst researchers at Ford Motor Company and their suppliers in the pursuit of this goal, which is to improve metal utilization efficiency through the development of a practical perovskite-based three-way catalyst.

Nontechnical Description: The solar-cell material CZTS is made of the low-cost, Earth-abundant elements Cu, Zn, Sn, S, and Se. Challenges to the development of high-efficiency CZTS solar cells include control of impurities and defects. This project is designed to gain a fundamental understanding of the atomic structure and local properties of defects in CZTS under electrical and optical excitations, using state-of-the-art transmission electron microscopy (TEM) in combination with novel in-situ TEM methods developed in the Principle Investigator's lab. These new techniques will allow us to directly probe the atomic structure of individual defects and the responses of those defects to an applied electric field and/or light illumination providing for the determination of the atomic scale structure-property relationships of individual defects. The result will be knowledge needed for the optimization of the material's microstructure and composition, advancing the development of low-cost and sustainable materials with improved properties for solar energy technology. In addition, this project provides a wide range of opportunities for the interdisciplinary education and training of undergraduate and graduate students needed in both industry and academic research today.

Technical Description: This SusChEM project is to study the structure and dynamic behaviors of Earth-abundant solar-cell materials using a combination of advanced aberration-corrected transmission electron microscopy (TEM) and novel in-situ TEM techniques. The research primarily focuses on thin films of kesterite Cu2ZnSn(S,Se)4 (CZTS), a candidate material to replace Cu(In,Ga)Se2 (CIGS). Because of the polycrystalline nature and the co-existence of multiple impurity phases in CZTS thin films, it is critical, but very challenging to understand the role of defects and interfaces in controlling the electrical properties and solar conversion efficiency. In this project, the PI combines the state-of-the-art aberration-corrected TEM imaging, spectroscopy, and the novel in-situ techniques recently developed in his lab to study the atomic structure and dynamic behaviors of individual defects, grain boundaries, and interfaces in CZTS materials. Spatially resolved cathode-luminescence and scanning tunneling microscopy holders with optical excitation, combined with holography and electron energy-loss spectroscopy (EELS), are used to identify the active and inactive regions of defects (grain boundaries, interfaces, secondary phase boundaries, etc.), while the atomic structure, chemical composition and local electronic properties of the same regions are determined by TEM imaging and spectroscopy with atomic resolution. In combination with the optoelectronic properties measured from the same material, the role of defects in controlling the materials properties can be understood.

NON-TECHNICAL DESCRIPTION: Materials with a particular crystalline arrangement of atoms, known as perovskite, have played important roles in applications ranging from electronic and magnetic devices to micro-machined actuators and sensors. Some of the most interesting phenomena arise at interfaces between these and other materials, where the atomic and structural aspects combine to form new materials in their own right. The main goal of this research is the discovery of a new class of interface materials based on antiperovskites. These antiperovskites exchange the atomic positions of the more common perovskites, creating unique, wide-ranging properties different from the parent materials. Interfaces between these two 'anti'-structures create unexplored fundamental opportunities for materials design. This research will discover the fundamental principles controlling these new materials systems, develop atomic-scale design principles, and create and explore these interfaces for potential applications in electronic, magnetic, and quantum-controlled devices.

TECHNICAL DESCRIPTION: Complex perovskite materials have been fertile ground for new discoveries, due particularly to their wide-ranging structural, electronic, optical, and magnetic properties. Interfaces between perovskites create juxtapositions between different symmetries and ordered states, and it has become clear that these interfaces are new materials in their own right, with inherently multiple length-scale distortions near the interface that lead to rotations, deformations, and electronic and structural orderings dramatically different from those in bulk. The main goal of this research is the discovery of a new class of interface materials based on antiperovskites. Antiperovskites have the perovskite structure, but cation and anion positions are interchanged, resulting in unique, wide-ranging properties different from perovskites. Interfaces between these two 'anti'-structures create unexplored fundamental opportunities for materials design. The fundamental principles controlling new physical phenomena at these interfaces will be determined, and the principles used to design couplings between multiple orders at interfaces to generate new functionalities. This research is aimed at developing atomic scale design principles for antiperovskite heterointerfaces, constructing databases of the stable interface structures, and developing antiperovskite heterostructures with scientifically important and technologically transformative structural, electronic, and magnetic properties. The project implements an integrated effort of theory, materials synthesis, structural, electronic, and magnetic characterization. The research will use an iterative approach, where feedback from experimental measurements of interfacial structure and electric and magnetic order is used to refine theoretical parameters and approximations. This iterative approach will develop a fundamental understanding of the interface atomic structure and bonding between disparate materials, and how it creates new interfacial spin order and electronic configurations. These atomic-scale interface materials will lead to new classes of controllable electronic and magnetic phenomena, and new growth approaches that will make possible heteroepitaxy of other materials systems with large disparity in structure and chemical bonding. The predictive theory and modeling, with feedback to theory from materials growth, and from structural, electronic, and transport characterization, will produce hetero-interfaces that have unique properties not presently available.

Nontechnical Abstract: The Materials Research Science and Engineering Center (MRSEC) at the University of California, Irvine (UCI) builds on UCI?s strengths in multidisciplinary science and engineering research to establish a major research hub for materials discovery and innovation in the Southern California academe-industry eco-system. The primary mission of this MRSEC is to establish foundational knowledge in materials science by developing new classes of materials that offer unique and broad functionalities. The MRSEC comprises two Interdisciplinary Research Groups (IRGs), each working in close collaboration to address Grand Challenges in national defense and human health. The first IRG aims to create materials which exhibit unprecedented physical properties, such as the ability to withstand extreme environments having applications in national defense. The second IRG team is addressing dynamic, responsive soft materials that are in essence living electronic materials serving as an interface with living systems for healthcare applications. Through seed projects, the UCI MRSEC engages new participants in exciting new research directions. It attracts a diverse group of scientists, including women, underrepresented minority groups, and persons with disabilities, from across the nation and trains future leaders at all academic and professional levels to address critical societal challenges. This MRSEC?s integrated activities?including novel materials research, partnerships with industry and national laboratories, entrepreneurial innovation, career development, and mentorship?are enabling a transformative long-term impact on fundamental science, advanced applications, and workforce development.

Technical Abstract: The UCI MRSEC combines an experimental, computational, and theoretical framework pursuing atomic- and molecular-level design and control of structure and dynamic response through two Interdisciplinary Research Groups (IRGs). IRG 1 investigates the atomic-level structure, chemistry, thermodynamics, and kinetics of interfaces in an emerging class of Complex Concentrated Materials (CCMs) that exhibit exceptional properties such as high strength, ultra-low thermal conductivity, and extremely large dielectric constants. Understanding their structure-property relationships guides design and processing of next-generation structural and functional materials. IRG 2 investigates dissipative self-assembly strategies to understand fundamental charge-matter interactions, with the goal to produce supramolecular ?living? materials. Development of conductive active materials, where assembly is fueled by chemical, electrical, and other stimuli, provides the intellectual framework for a new class of living electronic materials for bio-interfaces and biological computing. The research team leverages state-of-the-art electron microscopy facilities within the Irvine Materials Research Institute and pursues instrumentation innovations to characterize atomic-scale structure and dynamic properties. Multifaceted education, outreach, and collaborations with industry, national laboratories, and nonprofit organizations allow this MRSEC to achieve significant, long-term impact with the targeted scientific advances. This impact includes technological innovation, workforce development, and boosting of the regional and national economy. Synergistic activities provide holistic training of diverse junior scientists at all stages, from K-12, undergraduate, and graduate students to postdoctoral scholars and untenured faculty, further fostering inclusive excellence in STEM.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.