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3 The Research Program The Center for Nanoscale Science and Technology continues to address the challenge of actively managing the balance between high-quality science and service. The first can lead to the second, but only if time is allowed for the sufficient maturation of the research. The current balance is appropriate but needs to be monitored very closely if it is to be preserved. ELECTRON PHYSICS GROUP Scope and Mission The Electron Physics Group (EPG) conducts a wide range of cross-disciplinary research that focuses on developing innovative measurement capabilities for nanotechnology, with an emphasis on applications for future electronics. The EPG is the most established group within the CNST, having been a part of NIST since 1954. A number of the project leaders are among the founding members of the center. EPG research encompasses scanning-probe microscopy; nanomagnetic imaging and dynamics; theory, modeling, and simulation; and laser manipulation of atoms. The research conducted by the group is uniformly of a very high standard, and the capabilities in terms of the measurement tools and methods that the EPG is developing are impressive. Staffing The EPG consists of 20 scientific staff (5 project leaders, 11 postdoctoral researchers, and 4 visitors) in addition to 7 support staff (2 in electronics, 2 in instrumentation, and 3 in information technology). Although the support staff are attached to the EPG, they provide support for all of the CNST research groups. The EPG is well established, with senior staff having been in place for some time. The integration of postdoctoral researchers into projects is smooth, and there appears to be collaboration and communication across research areas and across groups. The input of the support staff is very important to these efforts, given the fact that much of the equipment is home-built. Staffing is adequate and is uniform across areas. Quality of Research and Facilities The scanning-probe microscopy is extremely strong and clearly a world-leading area. The instrumentation is unique in its capability, with the newest instrument combining a scanning tunneling microscope (STM) with high-energy resolution, cryogenic temperatures (10 mK), and high magnetic fields (15 T), and a range of ultrahigh vacuum (UHV) sample-preparation chambers. The quality of the research and the degree of collaboration with both internal and external researchers are excellent. The work on graphene addresses scientific issues that probably could not be addressed anywhere else. The emphasis on understanding changes to graphene that occur on its incorporation into device structures is critical. The EPG is very widely recognized and is a highlight of the CNST. The extension of scanning-probe microscope (SPM) 11
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spin-electronics measurements to topological insulators promises to be very fruitful as well. The integration of experiments with theory is also noteworthy. Three project leaders perform research that addresses nanomagnetism, including the following areas: (1) imaging using scanning electron microscopy with polarization analysis (SEMPA), (2) techniques to measure and quantify spin-wave modes, (3) the development of novel electron beams that carry orbital angular momentum (OAM), (4) the development of magnetic resonance force microscopy (MRFM), and (5) theory and modeling. The EPG has a strong presence within the nanomagnetics community, and its research, both experimental and theoretical, is highly regarded. The project leaders are continuing to develop new measurement tools that enhance their existing capabilities—for example, extension of SEMPA to analyze ultrathin magnetic multilayers by means of profiling using very-low-energy ion beams. The initiation of a program on transmission electron microscopy (TEM) beams with OAM opens up possible new applications and is to be encouraged. The experimental effort in the area of laser manipulation of atoms is superb. It is leading to an entirely new method of producing focused-ion beams through laser trapping of metallic atoms using a magneto-optical trap ion source (MOTIS). This method may enable focused-ion- beam (FIB) systems with a broader range of choices of source ion than is available in commercial systems. The ability to choose the source ion enables the optimization of the ion for the appropriate application: for example, for imaging, etching, pattern definition, beam chemistry, or materials analysis. The MOTIS also improves the energy resolution of the FIB instrument. The EPG interacts with industrial partners such as the FEI Company, a leading manufacturer of commercial FIB systems, through CRADAs and has patented aspects of the method. Alignment with Mission Research and development work in the EPG ranges from very fundamental work to applications with foreseeable technological or commercial applications. The EPG is involved in a wide range of interactions with collaborators from industry, academia, and national laboratories. Most of its collaborators are U.S.-based, although it is engaged in some international academic collaborations. NIST is a contributing member of the Nanoelectronics Research Initiative (NRI) funded by the Semiconductor Research Corporation (SRC). This involvement has led to 12 academic collaborations. Collaborators are helping the EPG to develop new measurement tools and also are acting as “users” of existing tools. The group’s industrial collaborators are somewhat fewer, although a strong interaction exists between the ion-beam development project and FEI Company. The new technique developed for measuring spin polarization by means of analysis of Doppler-shifted spin waves involves collaboration with Hitachi Global Storage Technology. Project leaders in the nanomagnetics area commented to the panel that collaborations with the magnetic-storage industry are becoming harder to set up. The difficulty is in part a result of the decline of that industry in general. The theory and modeling part of the program has strong interactions with academic collaborators and with other members of the EPG. These interactions are very appropriate and critical to the success of the EPG. In summary, all efforts of the EPG seem highly aligned with the overall mission of NIST in terms of measurement and the development of new methods. 12
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Future Plans The EPG has historically done very well in progressing from one exciting project to another. Well-positioned near-term ideas are apparent in a number of areas. Given the overall service mission of the CNST and the expectation of a continually changing base of collaborators, it may be difficult to develop plans beyond the short term. It will be helpful nevertheless for the research staff to have a plan and to update it continually in order to prioritize the wide range of high-impact activities and collaborations with which the group is becoming involved. Evaluative Comments and Suggestions Overall, the EPG is carrying out research that is cutting edge and of extremely high quality. The project leaders and postdoctoral researchers display a high degree of enthusiasm and commitment to their research, and there is clearly a positive work ethic. The presentations of the group were generally well organized and clear, and the posters were well presented by enthusiastic and knowledgeable postdoctoral researchers. Extensive written materials were provided to the panel. As noted above, the research being carried out in the group ranges from very fundamental to more applied, which is appropriate. A case in point is the research on focused ion beams, initially a basic research program that has now evolved into a CRADA and may result in a commercial product and a start-up company. The CNST takes seriously its role in preparing postdoctoral associates for their next position, and in general it does this very well. There may, however, be an opportunity for some enhancements that would enable postdoctoral associates to acquire skills that would be needed for non-academic careers. For example, training in entrepreneurship would be invaluable for postdoctoral associates contemplating starting a company or joining a start-up. If it is not possible to provide such training in-house, it may be possible to partner with neighboring institutions or to provide release time and resources. It is, of course, imperative to continue to make sure that postdoctoral associates, especially those who are more involved in service work than in research, have the opportunity to attend meetings and produce publications. The leader of the EPG identified the emerging requirement that measurements address novel electronics beyond complementary metal oxide semiconductor (CMOS) electronics, and provided a detailed list of potential devices for both memory and logic applications. The group should consider addressing the measurement needs of a wider range of these systems beyond magnetic materials and graphene. For example, technologies based on resistance change (both phase-change materials and resistive-switching oxide materials) have been identified as likely candidates for future applications, but they are attended by fundamental issues that would benefit from exploration by the techniques available in the EPG. NANOFABRICATION RESEARCH GROUP Scope and Mission The Nanofabrication Research Group (NRG) was formed in 2007. Its mission is to advance the state of the art in nanofabrication and nanomanufacturing. The research programs within the group cover a broad range, with a healthy mix of theory, modeling, and experiment. Several research projects that definitely do advance the state of the art of nanofabrication are outside the group—for example, the work on electron beams with angular momentum and that on focused-ion-beam extraction from optical traps, which are within the Electron Physics Group. 13
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This statement is not intended as a criticism but rather as an observation that technology advancements can come from many quarters, and this should be encouraged. Nano- manufacturing, an area of growing importance, has been added to the mission of the Nanofabrication Research Group since the previous review. Staffing The Nanofabrication Research Group has added new staff members since the previous review. It appears now to be appropriately staffed at the level of 8 project leaders, 14 postdoctoral associates, and 4 visiting fellows. The competence of the researchers was evident from their presentations and from their discussions with panel members during the laboratory visits. Quality of Research and Facilities The research programs within the Nanofabrication Research Group are of high quality. Group competencies include the following: nanofabrication, nanoscale stochastics, single- particle tracking, nanophotonics, nanoplasmonics, nanomechanics, nanotribology, in situ transmission electron microscopy, and nanosystems control. The laboratory facilities available to the group are among the best in the world. It is gratifying to see that such superb facilities are so widely available for service, collaboration, and the dissemination of information. Alignment with Mission The alignment of the research programs of the NRG with its mission of advancing the state of the art in nanofabrication is not uniformly obvious, although alignment with the overall mission of NIST is, in general, good. The research on nano-optics is focused on sensing and measurement. Although this effort is fully compatible with the NIST mission of measurement, it is only indirectly related to advancing the state of the art of nanofabrication. The research on nanomechanics covers both sensing and tribology. The former is fully compatible with the NIST mission of measurement; the latter is more basic in nature but with the potential to impact nanometrology significantly well into the future. The research on automated dual-beam nanomanufacturing addresses a serious problem with FIB systems and is definitely in line with the group’s stated mission of advancing nanofabrication. While awaiting the arrival of a new TEM, research on environmental transmission electron microscopy (ETEM) is employing instruments at the NanoFab, the NIST Materials Measurement Laboratory, and extramural organizations. Questions were raised about the validity of measurements made in an ETEM, as electron beams are well known to produce damage and could interfere with the phenomena being observed. That said, ETEM provides a unique means of monitoring events such as catalysis in real time, and the issue of intrinsic disturbance will be sorted out with further research. The in situ Raman thermometry extends Raman analysis into the ultraviolet (UV) to evaluate more materials and observe subtle phonon effects. The work on nanomanufacturing is welcome and is fully compatible with NIST’s mission of aiding U.S. industry. Much of the work in this area, especially the work on deconvolving substrate-particle interactions and on the high-throughput near-field scanning optical microscope (NSOM), is directly related to advancing the state of the art in nanomanufacturing. The convergence of these nondestructive methods shows promise for enabling a more fundamental understanding and control of buried nanoscopic structures, which is required for many 14
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nanomanufacturing processes. Focus on this issue will ensure that U.S. industry has ample opportunity to exploit innovations in nanoscale science and engineering. The plots of resolution versus throughput and complexity versus cost/area identify key problems. It would be beneficial if these plots could be further enhanced, clarified, and promulgated. The new emphasis on nanomanufacturing in the NRG is well integrated with initiatives at other agencies, including the National Science Foundation. Future Plans The NRG did not discuss future plans. The energy and youth of the staff and the intrinsic quality of the research, however, predict future success. Overall, the research, collaboration, and service of the Nanofabrication Research Group are exemplary. Now that the group is at full staffing, the connection with and synergistic emphasis on nanofabrication technology are likely to evolve significantly during the next review cycle. Evaluative Comments and Suggestions Research in the Nanofabrication Research Group is of high quality and well coupled to the NIST and CNST missions. The project leaders, postdoctoral researchers, and visitors are competent and enthusiastic. The presentations of the group were well organized and clear, but the posters were not. Some of the poster presentations were difficult to understand and lacked context or clarity of purpose or method. In the future, the review should have well-prepared posters or should eliminate them altogether. Given the critical importance of nanofabrication technology, a greater emphasis on research directed toward improving the efficacy and flexibility of nanofabrication methods is encouraged. This will require going beyond commercially available techniques, including those developed for the semiconductor industry. The Nanofabrication Research Group has hosted a number of workshops, which should be continued as a means of getting the NIST message out to the academic and industrial communities. ENERGY RESEARCH GROUP Scope and Mission The scope and mission of the Energy Research Group (ERG) are characterized as “developing measurement and fabrication methods relating nano-/atomic scale morphology and structure to functional properties in energy-related materials and devices.”12 Staffing The ERG is staffed appropriately with senior, junior, postdoctoral, and technical staff. There are currently 6 project leaders and 7 postdoctoral researchers. The hiring of a theorist with broad capabilities follows the recommendation made by the NRC review panel 2 years ago. The theorist’s work provides a needed intellectual coherence within the group. The prospects for 12 Nikolai Zhitenev, CNST/ERG, “The Energy Research Group,” presentation to the panel, Gaithersburg, Maryland, March 7, 2011. 15
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achievements resulting from the hiring of a physical electrochemist (consistent with another recommendation of the previous panel) with interests and a research style that fit well into the physics-oriented effort in the group are promising. The addition of a senior staff member to work on thermoelectric materials is a bold move designed to couple to industrial interests in this area. The group has also added a very strong senior researcher in nanotechnology and applications in energy. At this point, the Energy Research Group is relatively new, still growing, and coalescing as a unit. Quality of Research and Facilities The scope of ERG research is meant for the development of new measurements relating nano- and atomic-scale morphology and structure to functional properties addressing three areas: energy generation, energy conversion and storage, and energy efficiency. Five project areas are active: photovoltaics (PV), solar thermal energy, solar fuels, thermoelectrics, and batteries. The three core areas of measurement expertise are the following: (1) the theory and modeling of nanomaterials for renewable energy (calculations of electric, thermal, and ionic transport for materials and nanostructures used in energy-relevant applications, such as photovoltaics and thermoelectrics); (2) vibrational spectroscopy and microscopy (development and application of new spectroscopic methods, including infrared imaging with nanoscale spatial resolution, for characterizing nanomaterials with infrared and Raman spectroscopy); and (3) nanomaterials for solar fuels and artificial photosynthesis (methods to correlate structure and performance of nanocatalysts for solar fuels, and biotemplated approaches to artificial photosynthesis and nanofabrication). Examples of current research topics include the following: developing an understanding of structure/function correlations of photoanodes for water splitting, the in situ characterization of lithium-ion batteries, electrochemical measurements using surface plasmons, the fabrication and characterization of field emission sources based on arrays of 1D structures for x-ray sources, photothermal infrared absorption spectroscopy of condensed materials using atomic force microscope (AFM) detection, the development and characterization of nanostructured thermoelectronic materials, and nanoscale studies of charge transport in organic photovoltaic devices. The connection of this work to fundamental problems in physics, chemistry, and materials science is less clear than the connection to technological issues. For example, the selection of field emission arrays for investigation hardly addresses fundamental issues or recognizes the basic contributions to this field made at NIST in previous decades by the Electron Physics Group. The study of charge transport at nanoscale in organic photoelectric devices hardly recognizes the fundamentals of charge transport along molecules as currently achieved theoretically in fields such as molecular electronics and protein conduction. Despite being a relatively new group, the ERG has established projects to address a number of issues in the energy area. The quality of the research varies widely throughout the group. It was not clear to the panel whether many of the selected areas of energy-related research address the most critical problems of measurement in energy science. Certainly the investigation of field emission arrays, for example, cannot be connected to a major need in the energy field. The group should seriously consider the most important opportunities on the energy landscape in problem selection. The new laboratories, many of which are still under development, and new equipment are first rate in all respects. Most of the new equipment is commercial or modified-commercial. As the group continues to mature, it should aspire to the design and fabrication of some 16
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noncommercial equipment to address the frontier of nanoscale measurements connected to energy. Alignment with Mission The alignment of the Energy Research Group’s research program with the stated scope and mission of the ERG is appropriate. Future Plans The Energy Research Group has some good ideas and views with respect to its future research. However, long-range strategic planning for the group was not apparent and needs to be discussed more explicitly during the next review. Evaluative Comments and Suggestions The ERG is still very young. It is too early to judge the quality of the staff with accuracy, and it is even somewhat difficult to gauge the alignment of the work with the mission of the group and the mission of the CNST, as many laboratories are still under development. Over the next 2 years, the group needs to establish greater coherence, accompanied by the development of a stronger connection between nanoscale measurements and important problems in energy. The Energy Research Group is still in the process of growth and stabilization. Following are suggestions for the ERG as it moves forward: Over the next 2 years, it should establish greater coherence, accompanied by the development of a stronger connection between nanoscale measurements and important problems in energy. Although the new laboratories are outstanding, most of the equipment is commercial or modified-commercial. As the group continues to mature, it should aspire to the design and fabrication of some noncommercial equipment to address the frontier of nanoscale measurements connected to energy. Long-range strategic planning for the group was not apparent and needs to be discussed more explicitly during the next review. The CNST should continue the effort to mature the focus and stature of the newer research groups, especially the Energy Research Group. This effort would include more strategic planning and the identification of research issues of central importance to the energy landscape in the United States. 17