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Electron and Optical Physics Division

MISSION

The goal 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 using the NIST Synchrotron Ultraviolet Radiation Facility (SURF III). A number of very interesting supplementary research efforts are also pursued, as described below.

SCOPE

The Electron and Optical Physics Division, located at NIST’s Gaithersburg, Maryland, campus, has 1 Senior Executive Service (SES) staff member, 12 scientists/engineers, 1 technician, 43 NIST associates, and 1 administrative support staff, as of January 2010. Its FY 2009 budget was about $4.9 million, 81 percent of which was STRS funding.

There are several primary research focuses within the scope and mission of the Electron and Optical Physics Division. The largest program is that on the development of measurement capabilities for EUV optics, including both EUV metrology and damage issues; 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. A second focus area provides measurements and data to enable the development of atom and photon technology in sensors, atom interferometers, and quantum information-processing devices.

PROJECTS

The division has invested in upgrades of the SURF III facility that have made it an ideal source of extended ultraviolet radiation, and this facility now forms an important resource for several different activities. SURF III supports long-standing efforts in vacuum ultraviolet (VUV) and EUV detector calibration, which are an important part of the division’s core mission. Strong collaborations with the National Aeronautics and Space Administration (NASA) over several decades, and more recently with the National Oceanic and Atmospheric Administration (NOAA), have been essential to many different satellite missions. The implementation of a cryogenic radiometry capability has improved the accuracy of these calibrations by nearly an order of magnitude. Future improvements that will extend this methodology to shorter wavelengths will be very valuable.

EUV detector, source, and optical metrology activities have grown in recent years in support of the nation’s EUV photolithography technology. There are collaborations with several industrial partners that involve a unique capability to characterize large-area, large-numerical-aperture (NA), aspherical, multilayer-coated EUV reflection optics that



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3 Electron and Optical Physics Division MISSION The goal 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 using the NIST Synchrotron Ultraviolet Radiation Facility (SURF III). A number of very interesting supplementary research efforts are also pursued, as described below. SCOPE The Electron and Optical Physics Division, located at NIST’s Gaithersburg, Maryland, campus, has 1 Senior Executive Service (SES) staff member, 12 scientists/engineers, 1 technician, 43 NIST associates, and 1 administrative support staff, as of January 2010. Its FY 2009 budget was about $4.9 million, 81 percent of which was STRS funding. There are several primary research focuses within the scope and mission of the Electron and Optical Physics Division. The largest program is that on the development of measurement capabilities for EUV optics, including both EUV metrology and damage issues; 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. A second focus area provides measurements and data to enable the development of atom and photon technology in sensors, atom interferometers, and quantum information-processing devices. PROJECTS The division has invested in upgrades of the SURF III facility that have made it an ideal source of extended ultraviolet radiation, and this facility now forms an important resource for several different activities. SURF III supports long-standing efforts in vacuum ultraviolet (VUV) and EUV detector calibration, which are an important part of the division’s core mission. Strong collaborations with the National Aeronautics and Space Administration (NASA) over several decades, and more recently with the National Oceanic and Atmospheric Administration (NOAA), have been essential to many different satellite missions. The implementation of a cryogenic radiometry capability has improved the accuracy of these calibrations by nearly an order of magnitude. Future improvements that will extend this methodology to shorter wavelengths will be very valuable. EUV detector, source, and optical metrology activities have grown in recent years in support of the nation’s EUV photolithography technology. There are collaborations with several industrial partners that involve a unique capability to characterize large-area, large-numerical-aperture (NA), aspherical, multilayer-coated EUV reflection optics that 19

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are crucially important to the EUV program. This work cannot at present be done elsewhere in the United States; it is made possible by recent upgrades to the SURF III facility and experimental capabilities. A key barrier to the broad implementation of EUV lithography technology involves the development of new EUV photoresists, the generally polymeric materials into which a pattern is written when one is making small electronic devices. Successful implementation of EUV lithography is currently of dominant importance to the semiconductor industry. As yet, no photoresist offers the required combination of radiation sensitivity, spatial resolution, and low line-edge roughness. The division is actively pursuing some of these issues as well. A recent result demonstrating that a popular EUV photoresist is twice as sensitive as previously thought is very important and demonstrates the value of the division’s careful and precise EUV metrology efforts. The division has also established a collaborative program designed to further the understanding of resist photochemistry at the level of fundamental polymer chemistry. This is an important effort that will have a long-term impact on efforts to optimize resist performance. At present, the division does not have any EUV patterning capability. A grating-based EUV interferometer that can employ sources of limited spatial coherence to pattern lines with widths on the order of 10 nm has been designed and partly constructed. This instrument will be an important complement to existing capabilities, as it can be used to test the lithographic performance of existing and candidate photoresists. Completion of this apparatus should be pursued aggressively, along with synergistic collaborations with photoresist vendors and the Polymers Division in the Materials Science and Engineering Laboratory at NIST. The recent implementation of autonomous operation of the SURF III accelerator with about 0.3 A of circulating current, also a unique capability, has significantly expanded the capacity of the facility. This capacity represents an underutilized resource, and the division should consider research areas that might be developed in which it could have a major long-term impact. EUV surface photochemistry cuts across many different disciplines and laboratories, including plasma physics, space physics, optics, materials science, and several areas of chemistry. The SURF III-based EUV program is a common ingredient in all of these disciplines, and it increasingly acts as a focal point for EUV activities inside and outside NIST. The division should continue the active pursuit of more collaborations and connections to the growing industrial base focused on EUV lithography. There is a need for the development of a clear plan for central oversight of the entire NIST EUV program. In an additional VUV-based project, the division has participated in developing a new kind of neutron detector based on the production of vacuum ultraviolet radiation following the n + 3He → 1H + 3H nuclear reaction. By producing multiple photons per neutron that can be detected with a low-noise phototube, very high detection efficiency is possible. While originally thought to be hydrogen Lyman-alpha photons, more recent work suggests that the VUV light is related to noble gas excimers, which will significantly limit the bandwidth of the detector because of their long decay time and will limit the range of linearity with neutron intensity. This development should be pursued further to evaluate the advantages and disadvantages relative to existing neutron detectors. 20

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One of the newer research thrust areas supported within the Office of the Division Chief is Coherent Matter-Wave and Quantum Information Processing Metrology, which has focuses primarily in two areas. This first is nonlinear matter-light interactions in cold atoms, for sensors and atom interferometers; the second is a concentration on quantum communication. In the nonlinear cold atoms area, there are efforts in both theory and experiment. The theoretical program is well integrated with JQI activities supported by the Atomic Physics Division in the area of modeling magneto-optical atom traps and lattices loaded to an atomic density high enough that quantum effects are of primary importance. The experimental group in this research thrust area has developed a unique magneto-optic trap capable of creating high column densities of ultracold atoms. This trap can be used as a testbed for studying new quantum optical effects that will lead to new applications in quantum technologies. For example, the group is working on information storage and retrieval, and on fast gates utilizing this system and building on the insights that have come from quantum optical investigations of slow light in this system. Another fundamental investigation that combines both theoretical and experimental resources in the division is the detection of zitterbewegung in atoms. Analogous to the predicted but unobserved effect in electrons predicted by the Dirac theory of the free electron, this is a rapid oscillation in position caused by interference between atom and antimatter atom states. This experimental effort, though small, can take advantage of the large community at NIST of atomic physicists interested both in the fundamental aspects of ultracold atoms and in applications, particularly in quantum information. It is important that those connections be made as strong as possible in order to optimize the impact of this work. There is another small group within this thrust area, studying quantum key distribution (QKD) at high rates. This is a collaboration with several groups both within and outside NIST. The researchers are aiming at the development of transmission through the atmosphere of a polarization-encoded QKD system with a clock rate of over 1 GHz. Efforts have focused on optimizing the speed of avalanche photodiode detectors without sacrificing the quantum efficiency. This project involves a sophisticated integration of the optical and electronic system and custom high-speed electronics that adapt telecommunications clock-recovery techniques. This group has demonstrated continuous one-time-pad encryption of a streaming video signal, as well as one of the highest-speed quantum random number generation systems ever produced. It has taken successful live demonstrations to the highly visible DEFCON conference (the world’s largest hacker convention) for the past 2 years. The plans of this group are growing in response to increased interest to overcome a technical roadblock in the deployment of quantum information and communication systems. The division is pursuing several of these:  A key future advance in this technology will come from moving to the Balmer-alpha wavelength of 656 nm, where light from the Sun is attenuated by 7 dB in a narrow interval, greatly improving the fidelity of daylight operation of free-space QKD systems. 21

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 This group is also developing a fiber-laser-based source of correlated photon pairs, in collaboration with the JQI and the University of Illinois.  The data rates are sufficiently high that pixel-by-pixel entanglement of video images is possible, and the group is working to demonstrate this new video quantum image as a new milestone in quantum information. These efforts in quantum optics and quantum information within the Electron and Optical Physics Division are technically sound and well aligned with many other programs in the Physics Laboratory. They provide a strong conduit for communication among scientists in different divisions. This asset should lead to good coordination of effort across the Physics Laboratory in the crosscutting research activities. STAFFING The division currently supports 14 full-time-equivalent scientific staff, about half of whom are involved with SURF III operations and EUV technology development. This appears to fit the current diverse research scope reasonably well, although the ratio of research thrusts to scientific staff is low, and this suggests the need for some thought and organizational planning. The emergence of the SURF III facility as an important resource for EUV technologies suggests the need for a reexamination of the current management structure. The present arrangement, with the division director assuming primary responsibility for SURF/EUV operation, is not optimal. The overall program will benefit from strong and focused intellectual leadership and robust outreach to other NIST divisions and the broader EUV community in the United States. 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 and/or planned connection of this effort to such source development elsewhere at NIST (e.g., the Optical Technology Division) is encouraged. The division operates the SURF III facility and 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. Twenty years ago, this facility was used extensively for VUV 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. 22

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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 three criteria as requested by the NIST Director (see Chapter 1). Assessment Relative to Technical Merit 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;  On-site calibration capabilities for satellite EUV detectors;  The integration of EUV optical measurements with surface analytical photochemistry capabilities;  The high-rate testbed for secure quantum encryption key distribution in free space; and  The highest-column-density 60 mm-long magneto-optical trap for quantum optics and quantum information applications. Assessment Relative to Adequacy of Resources The SURF III upgrades have been very successful and useful, and the development of the quantum telecommunications laboratory has been very productive. The building that houses most division activities, including SURF III, 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. The implementation of the EUV interferometric lithography capability, as strongly recommended above, may be limited by environmental constraints. The primary reason that the EUV interferometric patterning apparatus has not been completed is budgetary limitations and the consequent lack of staffing. This is an important part of the EUV portfolio and should be pursued. Continued development of the SURF III EUV program will benefit from a group leader who will provide strong and focused intellectual leadership. Assessment Relative to Achievement of Stated Objectives and Desired Impact The Electron and Optical Physics 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 23

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30 percent of the aggregate effort. Each year, about 20 external users use SURF III, mostly for instrument calibration; about 30 photodiode and 5 deuterium gas (D2) lamp calibrations are performed; the reflectivities of between 50 and 100 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. This support offers good evidence of the value of the SURF III EUV programs. The division has a robust record of publication and presentations. Several workshops in the EUV technology area have been organized. CONCLUSIONS AND RECOMMENDATIONS The Electron and Optical Physics Division integrates a valuable, and in several cases essential, service component with cutting-edge, application-driven R&D. The division maintains a diverse portfolio of activities, and most collaboration is with researchers from other NIST divisions or from outside NIST. There is a need for strategic planning in which the division should consider what it wants to look like in 5 and 10 years and should address the following issues:  The improvements to SURF III operations will lead to increased EUV activity in the near term, and the division should develop strategic objectives and a leadership plan to make the best use of this resource.  The EUV lithography effort has gone in the direction of analysis of photoresists and analysis of damage to EUV optics. Both of these are bringing with them the need for increased local expertise in EUV photochemistry. The division should consider how best to organize this activity, through either strategic hiring or collaboration with chemistry and materials groups.  SURF capabilities are distinct from other user-facility sources in the EUV such as laser-plasma sources or VUV free-electron lasers. The division should consider how it integrates its activities with those of other sources. Current examples include support roles such as sharing calibration standards and collecting and distributing accurate data. As EUV applications expand, in both the commercial and the research sectors, new ways should be found to utilize the special value of the NIST activities. For example, a longer-term program in “EUV surface photochemistry” could be considered.  This division could play a leading role in the deployment of quantum communications and cryptography. The division currently houses an important primary resource in experimental quantum optics at NIST, and ways should be found to develop that leadership position to integrate this activity across NIST as well as in the emerging community of users of this technology.  The division should develop a strategic plan to help guide decisions about how to balance and strengthen the core activities properly and to decide on what is the correct balance of staffing and projects. All of the division’s individual projects are functioning at a very high level, but they are quite 24

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diverse. Synergy among projects in the division needs to be fostered. A solid strategic plan could suggest appropriate paths for organizing personnel among divisions in the Physics Laboratory so that the talented staff can work more closely with their collaborators in other divisions with a procedure that would more explicitly delineate the accomplishments of the contributing divisions and institutions. 25