An Assessment of the National Institute of Standards and Technology Physics Laboratory: Fiscal Year 2008 (2008)

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Electron and Optical Physics Division DESCRIPTION OF THE DIVISION Mission The general mission of the Electron and Optical Physics Division is to support emerging electronic, optical, and nanoscale technologies, particularly precision optical measurements in the EUV radiation range through the NIST Synchrotron Ultraviolet Radiation Facility (SURF III). A number of very interesting supplementary research efforts are also pursued, as described below. The departure of the Nanoscale Electronics and Magnetics Group because of reorganization seems to present a strategic opportunity for revisiting, clarifying, and/or redefining the division’s goals for the future. Scope With the movement of the Nanoscale Electronics and Magnetics Program to the new NIST Center for Nanoscale Science and Technology, there remain two primary research foci within the scope of the Electron and Optical Physics Division. First is the development of metrology for EUV optics, the maintenance of national primary standards for radiometry in the EUV and adjoining spectral regions, and the operation of national user facilities for EUV science and applications. The second focus provides measurements and data to enable the development of atom and photon technology in sensors, atom interferometers, and quantum information-processing devices. Projects Several current and future projects in this division that illuminate its core competencies, its connections inside and outside NIST, and its participation in various funding mechanisms are highlighted below. A major focus of the division concerns optical and source metrologies associated with the nation’s effort to develop photolithography in the EUV regime at the 13 nm wavelength. This approach is likely to be the future for extending Moore’s law (that the number of transistors on integrated circuits doubles about every 2 years) to enable faster computing through higher-resolution lithography. The division is heavily involved in characterizing the critical large-area, large numerical aperture (NA), aspherical, multilayer-coated EUV optics. The capabilities of the division in this area are unique and crucially important to the EUV program, as evidenced by its work with several customers of such optics (e.g., Intel Corporation and SEMATECH). This effort is important because EUV production facilities will use plasma sources having a broad angular distribution, and these require large-area and large NA collection optics. This work cannot at present be done elsewhere in the United States; it is made possible by recent upgrades to the SURF III facility, coupled to new instruments developed with funding under the America COMPETES Act of 2007. The implementation of autonomous operation of the accelerator with about 1 A of circulating current, also a unique capability, has allowed the division to test radiation damage to EUV optical surfaces 19 

under conditions that will be typical in future production facilities; the recent results from the division’s work in these areas already have important ramifications for such facilities. A key remaining barrier to the broad implementation of EUV technology involves developing new EUV photoresists, the generally polymeric materials into which a pattern is written when one is making small electronic devices. As yet, no photoresist offers the required combination of radiation sensitivity, spatial resolution, and low line-edge roughness. The division is developing a grating-based EUV interferometer that can employ sources of limited spatial coherence to pattern lines with widths on the order of 10 nm. This instrument will be used to test photoresists, but it also will serve as a useful testbed for similar measurements using laboratory-based EUV sources being developed for production facilities. It is not yet clear how strongly connected the division is to photoresist vendors; such connections might need to be pursued aggressively. Collaboration with the Polymers Division in the Materials Science and Engineering Laboratory at NIST would possibly be helpful on this project. EUV technology cuts across many different disciplines and laboratories, including plasma physics, optics, materials science, and several areas of chemistry. The SURF III- based EUV program is a common ingredient of significant utility in all of these disciplines, and it increasingly acts as a focal point for EUV activities at NIST. The division should continue active pursuit of more collaborations and connections to the growing industrial base focused on EUV lithography and a NIST EUV effort, to couple existing expertise in all of these areas. If NIST is to be a major contributor in this area, there is a need for the development of a clear view and possibly a plan for central oversight of this entire NIST EUV program. The unique capabilities of SURF III have facilitated long-standing efforts in detector calibration. Strong collaborations with the National Aeronautics and Space Administration (NASA) over several decades have been essential in many different missions; the division has brought key enabling capabilities to this collaboration. For example, recent activity will support the NASA European Venus Explorer probe, which will monitor solar weather and its impact on Earth’s climate. Also, the division has invested resources to improve its capabilities in EUV detector calibration. The implementation of a cryogenic radiometry capability has improved the accuracy of these calibrations by nearly an order of magnitude. Future improvements extending this methodology to shorter wavelengths will be of much value. The Electron and Optical Physics Division has spearheaded a recent, very exciting development of a new kind of neutron detector based on the production of Lyman-α radiation following the n + 3He → 1H + 3H nuclear reaction. By producing multiple photons per neutron, a very high detection efficiency is possible (only one or two of these photons needs to be detected). In addition to high quantum efficiency, this potentially transforming detector has much lower noise and much higher bandwidth as compared with existing neutron detectors. This development should be of interest in a variety of applications (including ones of relevance to health physics and homeland security) and to several agencies and vendors. The division should be encouraged to pursue this project and its numerous potential spin-offs. In the past several years, the division has assembled a small but state-of-the-art quantum telecommunications effort. The team performing this work has developed an ultrahigh-bandwidth detector that offers world-record speed for transmitting a quantum 20 

encryption key. The team members are now moving toward developing entangled and correlated photon sources for use with this system, a critical step toward reliable quantum communication. This program, which was developed in part with resources provided under the America COMPETES Act, appears to be well coupled to quantum physics groups across the Physics Laboratory, and as the NIST quantum information effort matures, this program should be a valuable component. The extent to which the quantum telecommunications team is connected to research outside of NIST is of concern; that is, at the moment its quantum communication testbed seems to be used almost exclusively for internal NIST research (in rather sharp distinction with most of the other activities of the division). The division should consider ways in which the quantum telecommunica- tions laboratory can better serve the greater research community outside of NIST. The division supports a small but active program in x-ray tomography. This effort is well connected to other groups inside and outside NIST. A recent project to develop a LEGO phantom (model) for tomography was well conceived and appears to provide a precise length standard for medical imaging. Such a standard could enable much more precise quantitative evaluations, for example of tumor growth. Staffing The division currently supports just under 20 full-time-equivalent of scientific staff, about half of whom are involved with SURF III operations and EUV technology development. This appears to fit the current research scope reasonably well. Since the implementation of third-generation synchrotron radiation facilities by the DOE, the SURF III facility has redirected its scientific program and has become an important ingredient of the nation’s effort to develop EUV technologies. With the right coordination and direction, the impact of SURF III and its associated EUV program could be even greater in the future. The former SURF III director, who retired several years ago, has not been replaced. Although the current arrangement with the division director’s assuming this responsibility works, the situation merits some review. The existing EUV- related activities at SURF III are individually strong and useful, but the overall program might benefit from focused direction and coordination. Such coordinated leadership of the SURF III EUV program will likely be essential if a compact x-ray source is purchased and operated by this division. Major Equipment, Facilities, Ancillary Support, and Resources The Electron and Optical Physics Division supports a state-of-the-art quantum telecommunications laboratory, as discussed above. The speed records of the system here are impressive; the division’s current move to develop sources of entangled and correlated photons for future studies is appropriate. Ongoing or planned connection of this effort to such source development elsewhere at NIST (e.g., the Optical Technology Division) is encouraged. The SURF III facility supports a variety of beam lines devoted to detector and instrument calibration as well as EUV optics testing, as discussed above. Several of these beam lines provide unique and important capabilities. The division operates the SURF III facility, as discussed above. Twenty years ago, this facility was used extensively for 21 

vacuum ultraviolet spectroscopy. In the early 1990s, however, many of those programs migrated to newer facilities around the country, leaving SURF III with a mission focused primarily on the core activity of detector and instrument calibration. The emergent role of EUV radiation in next-generation lithography has offered the facility a new mission of national prominence. This area should continue to be a major focus of this division. The division is also investigating the possibility of developing an x-ray facility using a compact source based on inverse Compton scattering. Such a source could provide a relatively narrow spectral width of the emitted x-rays, whose energy can therefore be optimized for particular applications. A commercial vendor exists that promises a product with performance comparable to a good bend-magnet line at a synchrotron radiation facility. Motivations for developing such a facility include developing metrology for an emerging tool that might have broad application, particularly in medical diagnostics and therapies; developing in-house x-ray microscopy and tomography capability; and spearheading a service to a broad spectrum of users around the NIST laboratories. The proposal has some merit but needs significant further development, for several reasons: 1. At present the vendor seems a little idiosyncratic, offering little detailed information about the source performance or characteristics. This is cause for concern. 2. The source is fairly expensive to purchase and to maintain, on the scale of common instruments at NIST. The division estimates that to purchase the source and to develop a single x-ray beam line would cost about $10 million. Annual operating costs would be about $3 million, or half of the division’s current budget. Some careful planning will be required for this single division to purchase and maintain this instrument and associated facilities. 3. The division, as well the rest of the laboratory, needs to undertake a cost- benefit analysis of developing and operating this facility compared with developing beam lines at an existing synchrotron radiation facility. A synchrotron bend-magnet beam line will cost perhaps $1.5 million to $2 million and will have significantly lower operating costs. Some of what the division wants to do could be done, perhaps better, at a synchrotron radiation facility, and the operating costs (to NIST) would be lower. Some of the metrologies associated with such an instrument that the division wants to pursue might not be easily done at a facility. Also, if compact sources such as the one under consideration achieve widespread use, for example in hospitals, there would be a clear advantage for NIST to research using that same approach. 4. The division should earnestly engage the biomedical community to determine how useful the planned instrument is likely to be in medical therapies. For example, to reach tumors deep inside the body, many cancer radiation therapies require x-ray energies well in excess of 1 MeV. It is not clear whether the commercial device will provide such high-energy photons. 5. The expense of developing and operating this facility suggests the need for sharing the responsibility with other NIST laboratories. The division should investigate this possibility, which it reports that it is doing. However, the 22 

currently available instrument serves as a single source. Serving too broad a community with a single source is known to cause problems at synchrotron radiation facilities. The many trade-offs between local control of a focused program and a broad program with a large user base need careful consideration. If the proposal is thought to be viable, a more focused review by a diverse panel of experts in x-ray, accelerator, medical, and material physics should be undertaken. ASSESSMENT OF THE DIVISION Following is the summary of the panel’s assessment of the overall quality of the Electron and Optical Physics Division (including opportunities for improvement) in terms of the charges from the Director of NIST. Technical Merit Relative to State of the Art The unique and state-of-the-art capabilities of the division include the following: • The precision reflectometry of large-area and large NA multilayer-coated EUV optics for at-wavelength testing and characterization; • The provision of transfer standard EUV photodiodes and the development of cryogenic radiometric capability, which improved calibration accuracy by an order of magnitude; • The primary national standard for source-based optical radiometry in the EUV regime; • The integration of EUV optical measurements with surface analytical capabilities; and • The high-rate testbed for secure quantum encryption key distribution (in free space). Adequacy of Infrastructure Supported by funding under the America COMPETES Act, the SURF III upgrades have been very successful and useful, and the development of the quantum telecommunications laboratory has been very productive. The building is old and lacks optimal environmental controls; although this is probably not a large impediment to most existing programs, it clearly affects program efficiency and, to a lesser extent, the morale of personnel. Achievement of Objectives and Impact The division supports an active and very useful service activity, combined with several application-driven research programs that will prove useful in facilitating future developments. The service activities amount to about 30 percent of the aggregate effort. Each year, about 40 external users use the SURF III mostly for instrument calibration, 23 

about 30 photodiode calibrations are performed, the reflectivities of between 100 and 200 EUV optics are measured, and the radiation damage testing of EUV optics is done for about 2,000 hours per year. The last three of these activities are performed on a cost- recovery basis and are supported by vendors, mostly in the developing EUV sector— which offers good evidence of the value of the SURF III EUV programs. These service activities appear to be valued within the division. The division has a robust record of publication and presentations. Several workshops in the EUV technology area have been organized. Programs Funded Under the America COMPETES Act The Electron and Optical Physics Division participated in two projects, discussed above, that received funding under the America COMPETES Act. The SURF III upgrade and EUV activities benefited from $475,000 of funding; the results have been positive. The quantum telecommunications project received $100,000, which has been very useful in continuing the development of this laboratory. CONCLUSIONS The Electron and Optical Physics Division integrates a valuable—in several cases essential—service component with cutting-edge, application-driven research and development (R&D). Funds under the America COMPETES Act have been put to good use, assisting in high-value service and R&D activities. The transfer of division staff to the newly formed NIST Center for Nanoscale Science and Technology resulted in a narrowed research portfolio for the division, which is probably good. Even after the reorganization, there remains a fairly diverse and seemingly somewhat disconnected research portfolio. There is a need for strategic planning. The division should consider what it wants to look like in 5 and 10 years and should address the following issues: • There will probably be increased EUV activity in the near term, but what happens as the technology is deployed? Does it make sense to complement the division’s EUV activities and expertise with laboratory-based sources like extreme ultraviolet (XUV) lasers and/or plasma sources? How does the division move from what is now a very valuable but largely support role in the EUV community into a role of intellectual leadership? • Is there broad support for a compact x-ray source at NIST, and would the division want to operate this as a user facility? If not, does the division have the resources and research program to run such a source independently? In the face of a multitude of x-ray beam lines in the United States and around the world, what would be the unique intellectual focus inside the division if such a facility were developed? How would these programs compare with others around the country and the world? How important are the coherence properties of a compact x-ray source to the proposed activities? Are there competing compact x-ray technologies on the horizon that need to be considered and evaluated? 24 

• What role will the division play in the coming convergence of quantum communications and cryptography? Will the division house the primary resource in experimental quantum optics at NIST? How can the quantum telecommunications laboratory serve the greater research community beyond NIST? 25