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Sensors and Electron Devices Directorate

INTRODUCTION

The Panel on Sensors and Electron Devices reviewed the research activity of the Sensors and Electron Devices Directorate (SEDD). The panel met at the Army Research Laboratory (ARL) facility in Adelphi, Maryland, on May 10-12, 2011, and May 22-24, 2012. During those two meetings, the panel reviewed research portfolios in all four SEDD divisions: Electro-Optics and Photonics, Energy and Power, Electronics and Radio Frequency, and Signal and Image Processing.

The review focused on both internal research projects and collaborative activities. SEDD is a lead directorate in the new Multiscale Multidisciplinary Modeling of Electronic Materials (MSME) Collaborative Research Alliance (CRA) and is a participant in multiple Collaborative Technology Alliance (CTA) programs focused on robotics, network sciences, cognition and neuroergonomics, and micro autonomous systems and technology. Several of its research centers and institutes focus on flexible displays, fuel processing, biotechnology, nanoscience, and microelectronics manufacturing. SEDD also participates in the International Technology Alliance (ITA) program in network science.

CHANGES SINCE THE PREVIOUS REVIEW

One of the most notable changes in SEDD is the evolution of the technical and scientific staff, which now numbers 332. SEDD employs a remarkable group of enthusiastic and talented people who are excited about the work they are doing and the environment in which they are doing it. In this cycle SEDD added talented staff in areas such as bioscience, intelligence analysis, and quantum information processing despite the highly competitive job market in these areas. Moreover, SEDD is to be congratulated for its successful recruitment of highly talented and impressive women and minorities among the new staff members. ARL’s programs supporting student interns, thesis projects, and postdoctoral fellows also are praiseworthy.



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4 Sensors and Electron Devices Directorate INTRODUCTION The Panel on Sensors and Electron Devices reviewed the research activity of the Sensors and Elec- tron Devices Directorate (SEDD). The panel met at the Army Research Laboratory (ARL) facility in Adelphi, Maryland, on May 10-12, 2011, and May 22-24, 2012. During those two meetings, the panel reviewed research portfolios in all four SEDD divisions: Electro-Optics and Photonics, Energy and Power, Electronics and Radio Frequency, and Signal and Image Processing. The review focused on both internal research projects and collaborative activities. SEDD is a lead directorate in the new Multiscale Multidisciplinary Modeling of Electronic Materials (MSME) Col- laborative Research Alliance (CRA) and is a participant in multiple Collaborative Technology Alliance (CTA) programs focused on robotics, network sciences, cognition and neuroergonomics, and micro autonomous systems and technology. Several of its research centers and institutes focus on flexible displays, fuel processing, biotechnology, nanoscience, and microelectronics manufacturing. SEDD also participates in the International Technology Alliance (ITA) program in network science. CHANGES SINCE THE PREVIOUS REVIEW One of the most notable changes in SEDD is the evolution of the technical and scientific staff, which now numbers 332. SEDD employs a remarkable group of enthusiastic and talented people who are excited about the work they are doing and the environment in which they are doing it. In this cycle SEDD added talented staff in areas such as bioscience, intelligence analysis, and quantum information processing despite the highly competitive job market in these areas. Moreover, SEDD is to be congratu- lated for its successful recruitment of highly talented and impressive women and minorities among the new staff members. ARL’s programs supporting student interns, thesis projects, and postdoctoral fellows also are praiseworthy. 61

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62 2011–2012 ASSESSMENT OF THE ARMY RESEARCH LABORATORY Improvement is also evidenced by increases in the numbers of publications, patents, and awards for scientific excellence. Refereed publications in 2011 increased by 36 percent and patent awards by 24 percent when compared to the average of the previous 4 years. Awards and recognition include 2 best paper awards, 2 scientific achievement awards from professional societies, and 11 Secretary of the Army Research and Development Awards, as well as election of a senior staff member as a fellow of the American Physical Society. SEDD has made a significant commitment to maintaining state-of-the-art microelectronics fabrica- tion facilities in-house through the Specialty Electronics, Materials, and Sensors (SEMACS) program. To this end, it invested $13.7 million over the past 2 years in new and updated cleanroom facilities and in other new facilities, including the Microsystem Indoor Testing Grounds developed for validation of autonomous microsystem devices under the Micro Autonomous Systems and Technology (MAST) program. The facilities provide essential support for Army-niche research and engineering activities in such areas as electro-optics and photonics, electronics and radio frequency devices, sensors, and power and energy. During the current review period, SEDD developed new relationships with industry and other Department of Defense (DoD) agencies and strengthened existing partnerships. Standouts among these relationships are the Flexible Display Center (involving more than 30 partners from industry, academia, and government, sharing a common goal of developing full color, video rate, flexible display technol- ogy for commercial and military applications); new partnerships in compound semiconductor devices with TriQuint Semiconductor and Cree, Inc., who perform manufacturing of compound semiconductor devices; and the MEMS (microelectromechanical systems) Exchange, which does device design and fabrication through a network of commercial, academic, and government foundries. SEDD has taken a leadership role in the ambitious new MSME CRA, which focuses on the devel- opment of a numerical toolset that can be used to build models that span many physics domains on a number of specific problems. With the breadth of knowledge at SEDD, and with the strong ties to the academic research community, SEDD and its partners are positioned to have a high impact in this area. ACCOMPLISHMENTS AND ADVANCEMENTS This section is organized by each of the SEDD divisions—Energy and Power, Electronics and Radio Frequency, Electro-Optics and Photonics, and Signal and Image Processing—and highlights some of the most significant accomplishments for projects within each. Energy and Power Division During this cycle, significant and encouraging advances in the division’s research vision and outlook reflect the evolution of the energy and power field in general, as well as the challenges facing the Army and ARL in particular. Division leadership recognizes that now is a great time to take advantage of the host of opportunities being offered to energy and power. Discussed below are some of the most notable recent accomplishments. Micropower The notion of a fully integrated (electronics and passives), single-chip power supply is an elusive goal in the power electronics business. SEDD researchers have made important progress, producing results that are among the best in the field. The first experimental results show Q values for air core

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SENSORS AND ELECTRON DEVICES DIRECTORATE 63 inductors greater than the state of the art. The magnetics are tunable to a remarkable degree, present- ing the possibility for improved voltage gain. This is one of the division’s most remarkable successes, with potential application to a fundamental Army need for miniature size and weight of power supplies. Passives SEDD’s work on high-performance and high-value passives has significantly advanced the state of the art. In particular, SEDD has demonstrated a miniature on-chip inductor fabricated by thick elec- troplating with high quality factors and high inductance density, which is the enabling technology for microscale power conversion technology. Smart Grid Technology SEDD researchers have begun building the tools and components necessary to implement smart grid technology in the tactical Army environment. They are building a hardware test and experimenta- tion facility to model the tactical command post’s integrated electrical power environment. Equipment includes a real-time digital simulator (RTDS)—cutting-edge equipment in the public electric utility industry—to enhance flexibility. SEDD has partnered with other agencies, notably the Department of Energy, for specific proposals, which aligns with the anticipated technology handoff to the U.S. Army Communications-Electronics Command (CECOM), which already has initiatives to do the tactical integration and networking. Related work in intelligent power management, energy harvesting, and micro-grid implementations has shown results that will enable soldiers to increase their reliance on electrical/electronic devices by reducing the weight loads on their shoulders. Fuel Cells Significant progress has been made in the area of fuel cells. In particular, a field test of an M100 direct methanol fuel cell system demonstrated that fuel cells can provide a high energy density, that will reduce logistics and provide both cost savings and weight savings. The new MSME CRA on electronic materials and electrochemical systems will substantially impact this program, and it will leverage com- putational expertise in academia with the experimental expertise at ARL. Batteries SEDD researchers have developed an additive to the electrolyte of lithium-ion batteries that modi- fies the solid electrolyte interface/interphase (SEI) layer chemistry and improves its stability, which has helped SEDD demonstrate the excellent voltage stability of Li-ion cells. This effort also involved computational work that proposed a reaction mechanism for the formation of the SEI layer. This is a good example of joint computational and experimental work. Work on the Li-Air battery also produced promising results toward developing a low-cost non- precious-metal-based catalyst: the developed catalyst lifted the discharge voltage by at least 0.2 V, improved discharge rate capability, and reduced cell reaction activation energy. Work on Li-La-Zr-oxide doped with Al to stabilize the cubic phase as solid electrolyte for lithium-based batteries also shows significant promise.

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64 2011–2012 ASSESSMENT OF THE ARMY RESEARCH LABORATORY Silicon Carbide (SiC) Electron Devices SEDD continues to be the leader in research in this field. SEDD has demonstrated a resonant 40 kV, toward 120 kV, DC/DC converter that uses SiC’s advantages of high voltage and perhaps higher tem- perature capabilities to meet SWaP (size, weight, and power) requirements. SEDD also has identified important packaging issues in the initial prototype. In other power electronics efforts, the implementation of SiC devices from large-diameter wafers for DC through pulsed applications is a significant achievement. Wide band gap semiconductors, particu- larly SiC, is a niche that ARL has filled well. ARL continues to be the leader in research in this field. Manufacturers continue to go to ARL for technical expertise. Similar efforts to find solutions in gallium nitride (GaN) and GaN-based materials have also seen progress. Extreme Energy In this transformational new project SEDD scientists collaborate with colleagues in biological sci- ences, physics, chemistry, and engineering to develop a technology for synthetic photosynthesis. With its interdisciplinary workforce and well-equipped laboratories, SEDD is well poised to succeed in this highly speculative enterprise. Automatic Reconfiguration of Power SEDD has begun to look at technologies that address power reconfiguration challenges. Specifically, there is a practical requirement to reconfigure power after battle damage and an economic advantage to reconfiguring equipment after it is deployed. SEDD recognizes this need and is investigating ways to address these issues in the context of Army environments and equipment. Electronics and Radio Frequency Division The portfolio of the Radio Frequency and Electronics (RF&E) Division ranges from fundamental electronic devices and sensor research to high-performance radar systems. This section highlights the recent accomplishment from this largest of the SEDD divisions. High Speed Digital to Analog Conversion SEDD researchers have developed advanced design techniques for ultra wideband digital-to-analog converters (DACs). In this cycle, they have designed and simulated an 8 bit, 32 GS/s DAC, which will be an essential component in future software-defined radio technology. MEMS SEDD maintains a thriving MEMS capability. The program’s applications range from RF compo- nents, to antennas, to small unmanned aerial vehicles. Accomplishments include fundamental materials development in graphene and piezoelectric and near-term devices such as the traumatic brain injury sen- sor. The latter is an outstanding achievement that will have an immediate impact on soldiers in the field.

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SENSORS AND ELECTRON DEVICES DIRECTORATE 65 Ultra-Wideband (UWB) Radar Processing Researchers have developed a clever algorithm based on single-value decomposition that reduces the amount and intensity of clutter returns while maintaining target returns. In addition, a second algorithm has been implemented that uses compressive sensing to eliminate the degrading effects of interfering signals. This may be the first successful use of compressive sensing for this application. Electro-Optics and Photonics Division This section highlights several projects from the Electro-Optics and Photonics Division (EO&P). Although biological science research is also housed in EO&P, SEDD undertook in 2012 a separate review focused exclusively on ARL research related to biological science. This section focuses solely on EO&P projects. Quantum Dots Quantum dots have been known to enhance the light absorption through multiple energy levels in photo sensors. They can also extend the absorption edge into the infrared range of the light spectrum. SEDD researchers are investigating the effects of quantum dots with build-in charge on the solar cell harvesting and recombination process. SEDD researchers have achieved an increase in the power effi- ciency of an InAs/GaAs quantum dot solar cell from 9 percent to 14 percent. High-Performance IR Detectors Resonator quantum-well infrared photodetectors (QWIPs) continue be a crown-jewel achievement of SEDD. SEDD has been able to incorporate advanced optical concepts into the detector design. SEDD has developed a better understanding of new near-field optical phenomena that has enabled design of a QWIP structure with quantum efficiencies of nearly 70 percent, doubling the previous record of 35 percent for corrugated QWIPs. SEDD is also investigating advances in infrared detectors based on HgCdTe. Specifically, the approach is to replace tellurium (Te) in the existing HgCdTe by selenium (Se). This is work in progress, but preliminary results indicate that some improvements have been obtained. Optoelectronic Oscillator EO&P research aimed at creating an extremely low noise oscillator has produced outstanding results. SEDD researchers have found a way to build a 10-GHz optoelectronic oscillator that matches the specifications of commercial low-noise oscillators up to 10 kHz away from the carrier at an order- of-magnitude lower cost and competitive size and weight specifications. This accomplishment will be of great interest to the radar community for the detection of small targets in clutter. Cold Atom Optics The underlying notion behind cold atom optics is that everything in conventional electronics, from wires to batteries to transistors and diodes, can be replaced by atom analogs. The project’s objective is to explore the possibility of using atom spin instead of electron spin to make novel spintronic devices.

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66 2011–2012 ASSESSMENT OF THE ARMY RESEARCH LABORATORY Specifically, the spin polarization of atoms trapped near the surface of a microfabricated semiconductor chip will be controlled, eventually to transport the atom spin along the surface of the chip. Ultimately, this could lead to an atom-based spin transistor. Spin-polarized atoms will open up more possibilities for advanced technology in computation, signal processing, and sensing than are available with spin polarized electrons. Coherent control and entanglement of neutral atom qubits confined on an atom chip by means of an optical frequency comb can potentially replace the well-known trapped ions. This technology relies on a laser to cool atoms to very low temperatures. The temperature achieved in a laboratory demonstration of this technology was a remarkable 40 × 10 –6 K. Ultraviolet Lasers SEDD, in collaboration with the University of Central Florida, has demonstrated high-quality AlGaN/Ga:MgZnO grown on sapphire, which is extremely important for implementing high-efficiency near-ultraviolet lasers. Signal and Image Processing Division A large part of the signal and image processing effort within SEDD is collaborative work with CISD as part of the Network Science Program. This research is discussed in Chapter 2. This section highlights additional projects within the Signal and Image Processing (S&IP) Division. Image Processing for Facial Recognition SEDD researchers have demonstrated a capability to enhance the performance of low-resolution security cameras so that the images can be used to improve the verification rate of automatic facial rec- ognition algorithms. This important result will enable more effective use of security cameras to protect guarded facilities and will allow law enforcement to make far better use of security cameras to address serious threats. A parallel effort has focused on devising machine recognition methods for detecting humans in stationary scenes. This collaborative effort draws on SEDD’s machine recognition skills and super- resolution technology and CISD’s social-cognitive work. Because human experts have almost always outperformed every other approach, the long-term promise of this technique is enormous. This work demonstrated the ability of recognition algorithms to identify humans in challenging scenes, such as those with partially obscured targets. OPPORTUNITIES AND CHALLENGES SEDD faces the challenge of building an innovation ecology that generates novel technology to enable the warfighter. In doing so, it needs to create an organic and bottom-up environment for its researchers to innovate, yet this environment should be constrained to insure that the needed technologi- cal innovation is there to support the warfighter. Balancing the need to constrain an open technology innovation environment is not an easy challenge. SEDD leadership is aware of the delicate balance that they need to have in place to catalyze innovation and the need to actively, but not intrusively, intervene to keep the ecology in synchrony with the SEDD mission. The rotating SEDD directorship is not healthy for the organization. Talented division chiefs have served as director for 4-month intervals, which is not sufficient time to allow for (1) sustained and con-

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SENSORS AND ELECTRON DEVICES DIRECTORATE 67 sistent assessment of how the customers’ needs match with the current research and development activi- ties; (2) alignment of funding and personnel resources in the light of shifting missions and budgets; and (3) tweaking of the constraints to adjust the flow of innovation. A permanent director is needed for SEDD. The recently initiated multiscale modeling CRAs are ambitious yet necessary efforts. ARL is to be commended for establishing the two CRAs, the MSME, and the Materials in Extreme Dynamic Envi- ronments (MEDE). Under the MSME, a multi-university team is charged with doing the fundamental multiscale modeling on lithium batteries, fuel cells, electronic materials, and devices. ARL will perform the supporting experimental work. Given the substantial issues concerning the premise of bridging the scales in multiscale modeling, many challenges (and thus opportunities) exist in demonstrating verifi- able success in the 5-year timeframe. Close interactions of ARL personnel with the multi-university team selected will be critical to ensure a focused and productive group effort. A potential challenge is to make sure that the multi-university team, with principal investigators having different (not necessarily overlapping) skills, remains focused and delivers value to ARL. Work on the MAST program has been impressive. However, supplying ample power to autonomous devices is a challenging problem, and it is not clear whether a solution is in sight. Work to design a fully integrated MAST with power onboard may be needed and may lead to a system design that is achiev- able in a realistic timeframe. ARL has outstanding fabrication facilities. Many projects that use the facilities also require micro- structural characterization at the nanometer scale. SEDD, and more generally ARL, should make every effort to ensure that characterization facilities, such as high-resolution and analytical electron micros- copy, are readily available. Moreover, in-house characterization capabilities will have to keep pace with the quality of the fabrication equipment. OVERALL TECHNICAL QUALITY OF THE WORK The quality of research being conducted within SEDD is excellent. This is reflected in the numerous awards received by the SEDD scientific staff, by the number of refereed publications authored and co- authored, and by the number of presentations given at professional society meetings. By these metrics, ARL compares favorably with other private and university-based research institutions. There is no doubt that SEDD is conducting world-class research. SEDD researchers are efficient at leveraging ongoing research that appears in the technical literature, at technical conferences, and through contacts with active researchers. They have the enormous task of understanding the needs of an astonishingly broad range of Army applications and then providing innovative solutions. From a technical viewpoint, they are performing this mission quite well. It is impressive that in this context SEDD endeavors to predict Army needs that are one to two decades out. For example, extreme energy science has been identified as a strategic initiative for the laboratory. In response, SEDD staff has successfully combined in-house capabilities and external col- laborations to quickly lead the scientific community working in this nascent field. The ARL/SEDD policy of involving undergraduates, graduates, and postdoctoral fellows as part of in-house research efforts is not only a wonderful vehicle to educate the nation’s workforce but also a great coupling with educational institutions that might or might not have formal research contracts with ARL. This practice is beneficial to all involved, and its continual implementation should be encouraged.