Chunhui Dai Receives First Place in NSF Student Research Poster Competition

Doctoral student Chunhui Dai has been awarded first place in the National Science Foundation student research poster competition. The competition was held at the 2018 International Mechanical Engineering Congress and Exposition (IMECE) in Pittsburgh, PA in November. The poster is titled “In-Situ Monitored Self-Assembly of 3D Graphene-based Nanostructures.” Chunhui’s poster was selected from more than 100 posters that participated in the competition. He is conducting his research under the guidance of Prof. Jeong Hyun Cho.

Chunhui with award-winning poster

The technique Chunhui demonstrates in the poster has the potential to be used for rapid and ultra-sensitive detection of biological analytes. It can be applied in medical diagnostics, environmental monitoring, and food safety.

Molecular sensing provides critical information about chemical and physiological processes, which plays a key role in disease detection and treatment. Graphene has recently demonstrated the ability to confine light near its surface and react with an attached molecule, thereby generating a detectable infrared signal. However, as graphene is a two-dimensional material, any sensing activities are restricted to its surface, thus limiting its overall sensitivity. Inspired by the art of origami, Chunhui’s research interest lies in developing a self-assembly process to fold 2D graphene into 3D graphene-based nanostructures, which have the potential to achieve greater light confinement, thereby increasing their sensitivity.

Currently, Chunhui is working on using these structures to analyze haemoglobin for detecting diseases. And in conjunction with other members of Prof. Cho’s research team, he has submitted a proposal to use this technique to study circulating tumor DNA for predicting cancer.

Chunhui received his bachelor’s degree in electrical engineering from State University of New York, Binghamton in 2014, after which he commenced his doctoral program in ECE. Fabrication of 3D nanostructures, the prospect of working with Prof. Cho in this area, and the potential to pursue cross-disciplinary research, drew Chunhui to the University.

Internet of Things Student Project Showcase

Students display their understanding of software development and hardware skills acquired in class

Every semester, during the last week of classes, there is the usual feverish studying for finals week, and turning in the last of the assignments. But amidst this frenzy there is also a quiet excitement tinged with pride that is radiated by the EE 1301 class, as they prepare for the Internet of Things showcase.

The showcase is a culmination of the semester-long four credit course EE 1301: Introduction to Computing Systems. The course introduces students to programming in general, and specifically using C/C++, emphasizing applications in microcontrollers, physical computing, and the Internet of Things (the Internet of Things is where the world of analog, of devices, appliances, vehicles, tools, are connected to the Internet, and can be controlled or activated remotely by devices such as a laptop or smartphone). While students engage in some intensive conceptual learning in the class, the strong hands-on, practical component of the class is what excites them most. In keeping with that, the final deliverable for EE 1301 is an open-ended student-directed group project, which the groups publicly display at the ECE IoT Showcase.

Some of the projects students have created include an internet Connect 4 game with an LED display, a sign language interpreting glove, LED-matrix Breakout game, an elder-care monitoring system, and a pet cooling blanket.


Besides the core concepts, by the end of the semester, students have also developed some transferable skills such as developing and pitching a project concept, working in teams, and debugging combined hardware and software problems.

Given the conceptual and experiential nature of the course, not surprisingly, student feedback on the course has been positive. They are eager to take ownership of their ideas, see it to fulfillment, and proudly exhibit it at the showcase at the semester’s end. ECE faculty such as Kia Bazargan, David Lilja, David Orser, and John Sartori who teach the class, view the driving force of the course to be the opportunity for students to use their creativity and personal interests to develop a new and exciting project concept. They then use the hardware and software development skills learned in class to build something entirely new.

One of Prof. Sartori’s students, referring to a job he landed based on his EE 1301 project, had this to say about the course: I would not have gotten interested in IoT or machine learning, started MKono (the hobby project you encouraged me to start), or known about IoTHackDay. I have you to thank for this job.


The IoT showcase is held during the last week of classes, every fall and spring semester, on the third floor atrium of Keller Hall. Stop by and check our students’ work; the showcase is free and open to the public.  

Prof. Rhonda Franklin Receives IEEE MTT-S’ N. Walter Cox Award

In recognition of her exemplary service to the IEEE Microwave Theory and Techniques Society, Prof. Rhonda Franklin is the 2019 recipient of the N. Walter Cox Award. The citation reads: “The award recognizes an individual who has given exemplary service to the Society in a spirit of selfless dedication and cooperation. The award is instituted in memory N. Walter Cox, a longstanding MTT-S volunteer.”

For Prof. Franklin, the award is a timely acknowledgement of her work as an active and engaged member and volunteer of the MTT-S group. As a researcher, educator, and volunteer, she has displayed her leadership, and selfless spirit in all her undertakings. Her active engagement with the Society began in 1996, at the start of her professional career. Since then, she has undertaken a variety of tasks ranging from reviewing technical papers for the Society’s journals, serving as editor in various capacities, serving on the International Microwave Symposium (IMS) steering committee, several sub-committees, judge for several student paper competitions, and organizer for various workshops and panels. She has also served as a scholarship chair, and has been elected to serve as chair of the Technical Coordinating Committee for Packaging, Integration, and Manufacturing starting in 2019.

However, besides these activities, what has been most profoundly significant for Prof. Franklin and for the many individuals she has influenced, is her work with minority and women students, developing and encouraging their interest in microwave theory, facilitating research and workplace skills development, and actively mentoring them to successfully take on leadership positions in engineering and academia.

Prof. Franklin is driven to inspire, encourage, and empower minority and women students to be the future generation of engineers, scientists and leaders.

PROF. FRANKLIN AS MENTOR

In 2014, Prof. Franklin co-founded IMS Project Connect which is aimed at familiarizing undergraduate and first year minority and women students with the microwave community and industry by facilitating collaboration with the MTT Society through the symposium. She has worked with co-founders, professors Thomas Weller and Rashaunda Henderson, to plan the program which includes developing communication and networking skills, understanding workplace expectations, career opportunities in microwave engineering in industry, academia, and government, and facilitating meetings with industry leaders and scientists. Participants not only engage in these opportunities, but are also expected to turn in a video conveying the import of the experience for them, titled, “IMS through Their Eyes.” A success from its inception, thanks to the strong support and commitment of all volunteers involved, the program is among the first of its kind within IEEE, where a professional society teams up with an undergraduate student education program to impact STEM education.

A leader, mentor, and teacher, Prof. Franklin is eager and enthusiastic to understand how an organization or unit operates, actively listens to ideas and contributions, and works hard to  integrate them to resolve problems, and create new initiatives. These are qualities she has demonstrated as an MTT-S volunteer and researcher, who has enthusiastically encouraged, inspired, and supported future generations of women engineers, and continues to do so each day.

Prof. Franklin’s steady commitment is borne out by awards she has previously received:

  • 2017 John Tate Advising Award
  • 2104 Sara Evans Faculty Scholar/Leader Award
  • 2012 CIC Academic Leadership Fellow
  • 1998 Presidential Early Career Award for Scientists and Engineers (PECASE)
  • 1998 National Science Foundation CAREER award
  • 1998 Professional Engineering Society Council’s Advisor of the Year Award (University of Illinois, Chicago)
  • 1997 Amoco-Silver Circle Award for Teaching Excellence (University of Illinois, Chicago)

And these are just a few of the several she has received. The award will be conferred at the Society’s annual Awards Banquet scheduled during the International Microwave Symposium (June 2-7, 2019) in Boston, Massachusetts. The Department of Electrical and Computer Engineering congratulates Prof. Franklin and thanks her for her selfless service and dedication.

Learn more about Prof. Rhonda Franklin’s research

 

Haoran Sun Receives Best Student Paper Award at Conference on Signals, Systems, and Computers

Doctoral student Haoran Sun is a recipient of the best student paper contest at the 2018 Asilomar Conference on Signals, Systems, and Computers, for the paper “Distributed Non-Convex First-Order Optimization and Information Processing: Lower Complexity Bounds and Rate Optimal Algorithms.” A prestigious prize among signal processing conferences, Haoran’s paper competed against 86 student papers, and came in at third place, among the 8 finalists.

Haoran’s work addresses decentralization of information processing. The next decade will see an estimated 50 billion connected smart devices providing data, services, and ubiquitous real-time information, touching all aspects of our lives, from healthcare to entertainment. Such a scenario necessitates a paradigmatic shift in the way that information processing, computation, and resource management are handled. One promising solution is to move away from the centralized client-server protocol, towards decentralized processing at the network edge. Such decentralization can effectively manage the increasing number of distributed devices and the surge in data, and meet the stringent latency requirements.  

Haoran’s research focuses on such a distributed setting and addresses the question of identifying and achieving the best possible performance for distributed optimization and machine learning. The conference paper presents methods and algorithms capable of using large scale distributed resources such as data and computational power, to perform fast, decentralized, and scalable computation. In the paper, Haoran derives the fundamental performance limits for a class of challenging distributed optimization problems, where multiple nodes collectively optimize certain non-convex functions using local data. He presents an  optimal algorithm, which enables the nodes to find high-quality solutions using the least amount of communication and computational resources.

Haoran Sun earned his Bachelor of Science in Automatic Control from Beijing Institute of Technology, China, in 2015, and earned his Master of Science in Industrial Engineering from Iowa State University in 2017. He is currently pursuing his doctoral degree under the guidance of Prof. Mingyi Hong. His research interests include optimization, machine learning, and its applications in signal processing and wireless communications.

Prof. Jian-Ping Wang to Lead a $10.3 Million Spintronic Materials and Devices Research Center

The University of Minnesota has received funding to the tune of $10.3 million to establish a research center on spintronic materials and devices. The funding comes from National Institute of Standards and Technology (NIST), and its partners in the Nanoelectronic Computing Research (nCORE) consortium, which includes the Semiconductor Research Corporation (SRC), 12 semiconductor industry sponsors, and the National Science Foundation (NSF).

Called Center for Spintronic Materials in Advanced Information Technologies (SMART), it will be led by the University’s Distinguished McKnight University Professor and Robert F. Hartmann Chair in Electrical Engineering, Jian-Ping Wang as director. It will also include researchers from Georgetown University, Massachusetts Institute of Technology (MIT), Pennsylvania State University, and the University of Maryland.

Spintronics (where the spin properties of electrons are harnessed) offers several advantages over conventional electronics such as higher speeds, improved energy efficiency, and greater stability. SMART will bring together experts in spintronic materials and device innovations, which will define new computing paradigms such as neuromorphic computing, probabilistic computing, in-memory computing, and wave-based information processing.

Prof. Wang explains, “Future computation systems will place heavy emphasis on computational paradigms such as neuromorphic structures for cognitive computing, in-memory computing for big-data applications, and reconfigurable structures that are adaptive to changing application needs. These systems will need to be error-resilient and will require high-endurance devices. Spin-based materials and devices provide an ideal platform to satisfy these requirements, and they have been shown to map naturally to these computational paradigms. The inherent non-volatility of spintronic materials, along with the ability to precisely control interactions between them, offer abundant possibilities for developing novel spin devices for a wide variety of information processing needs.”

Future computation systems will have to be error-resilient and will require high-endurance devices. Spin-based materials and devices satisfy these requirements.

To make such devices and bold new paradigms a possibility, spintronic materials have to be further developed and fine-tuned. SMART will be a fully integrated, multi-institutional, and cross-disciplinary program.

Associate director of SMART, Prof. Caroline Ross, Toyota Professor of Materials Science and Engineering at MIT emphasizes the cross-disciplinary nature of the Center. “Driven by the needs of well-defined next-generation computing architectures and paradigms, SMART is a materials-focused research center that also incorporates development of spintronic devices and measurement and metrology techniques.”

The SMART research portfolio is organized around advanced spintronic materials research. The research themes focus on three classes of spintronic materials that have shown exceptional promise in recent years: novel spin-orbit torque materials, ultra-low loss spin-wave materials, and magneto-ionic materials. These themes are supported by principal investigators (PI) performing cross-theme tasks in modeling, state-of-the-art characterization techniques, and a multi-theme focus on developing industry-compatible manufacturing technologies. Collaborations with other SRC centers will develop SMART materials and devices for use in novel computing paradigms.

University of Minnesota successfully housed the STARnet C-SPIN Center in the past five years.

Learn more about Prof. Jian-Ping Wang’s research

Click here for the NIST news release

 

 

 

Prof. Sachin Sapatnekar to lead $5.3 million federal grant to improve electronic circuit design

The University of Minnesota recently received a four-year, $5.3 million grant from the Defense Advanced Research Projects Agency (DARPA), an agency of the U.S. Department of Defense, to lead an effort that could spark the next wave of U.S. semiconductor innovation and broaden the competitive field for circuit design. Integrated circuits power almost every electronic device we use today.

The University of Minnesota is one of only 11 lead universities or companies to receive funding from the DARPA Intelligent Design of Electronic Assets (IDEA)  program, a new program under the DARPA Electronics Resurgence Initiative. Other partners on the University of Minnesota-led grant are Texas A&M University and Intel, a leader in the semiconductor industry.

The complex circuitry in today’s semiconductor chips is built using software that automates the design of analog and digital circuits, but consumers continue to demand even more complex chip designs.

Today’s system-on-chip platforms incorporate billions of transistors with miles of electrical wiring that are integrated within a tiny chip. This technological feat requires large teams and complex software. As a result, the cost of circuit design continues to skyrocket, narrowing the competitive field to large, multinational companies capable of keeping up with the demand for capital and skilled talent. It’s becoming increasingly difficult for small entities, as well as the Department of Defense, to leverage the high-performance technology it needs to design complex circuits for defense applications.

“The high cost of this software creates a barrier to entry for smaller entities to compete in design efforts,” said Sachin Sapatnekar, a University of Minnesota professor of electrical and computer engineering who will lead the grant. “The goal of our research is to replace the proprietary model with an open-source software environment for analog and mixed-signal designs. In short, we seek to ‘democratize’ chip design by facilitating open access to chip design tools and seeding a
community of users. The result will be lower costs to consumers for electronics.”

Through the creation of a software-based, completely automated physical layout generator and an open-source intellectual property (IP) ecosystem, the IDEA program aims to create a “no human in the loop” layout generator that would enable users with limited electronic design expertise to complete the physical design of electronic hardware within 24 hours. The software created under IDEA would be capable of automatically creating circuit design files ready for manufacturing, reducing design time from months or years to a single day.

By applying machine learning methodologies, IDEA hopes to continuously evolve and improve the performance of the layout generator for digital circuits, mixed-signal integrated circuits, systems-in-package, and printed circuit boards.

“Through the IDEA program, DARPA aims to eliminate the Department of Defense’s resource and expertise gap associated with custom electronic hardware design for the most advanced technologies by enabling full automation and applying machine intelligence,” said Andreas Olofsson, the Microsystems Technology Office program manager leading IDEA. To read more about DARPA’s IDEA program and the newest round of funding, visit the DARPA website.

Congratulations to Eric Konitzer on the DEPS Scholarship

ECE graduate student Eric Konitzer is a recipient of the 2018-2019 Directed Energy Professional Society (DEPS) scholarship. Eric works with Prof. Joey Talghader in his optical MEMS group, investigating the next generation of infrared detectors for long wavelength infrared light. These sensors could eventually be used for very high precision thermal imaging. Specifically, Eric is examining how micro scale devices are prone to vibrations due to thermal energy. Although this effect is typically considered undesirable noise in MEMS systems, the optical MEMs group uses it to to their advantage as part of the design. Eric has been fabricating MEMS structures, and evaluating fabrication and measurement capabilities to learn what to expect for thermomechanical noise in some typical systems. Going forward, Eric will work on creating more complex structures that exploit materials’ properties in ways that can maximize an infrared detection signal. After graduation, he plans on working in related industry in research and development.

DEPS is the leading organization that facilitates and promotes communication on the development and application of directed energy (DE) (high energy lasers, and high power microwave systems and technologies). The Society supports research and development of directed energy technology for both defense and civil applications. Academic disciplines engaged in DE research include physics, electrical engineering, chemistry, chemical engineering, materials sciences, optical sciences, optical engineering, and aerospace engineering.

The deadline for the next round of scholarships (2019-2020) is April 12, 2019.

Congratulations to Our 2018-2019 Doctoral Dissertation Fellowship Winners

The recipients are Yanning Shen (advisor: Prof. Georgios Giannakis), Hari Cherupalli (advisor: Prof. John Sartori), Ahmed Zamzam (advisor: Prof. Nikos Sidiropoulos), and Zhengyang Zhao (advisor: Prof. Jian-Ping Wang).

 

Yanning Shen

Yanning Shen’s research interests are network science, big data analytics, and nonlinear modeling. Fittingly, her dissertation has to do with the introduction of nonlinear models and scalable online algorithms for inference and learning over large-scale dynamic networks. Her work aims to develop a unified framework to capture the dynamics and non-linearities in real-world networks. The title of her dissertation is “Topology identification and learning over graphs: Accounting for nonlinearities and dynamics” and she is working under the guidance of Prof. Georgios Giannakis. The outcomes of her research will benefit several domains such as social networks, epidemiological studies, transportation, financial networks and brain networks. For instance, with respect to brain networks, Yanning’s research can significantly enrich the information provided by an MRI and highlight key features that distinguish abnormalities from what is normal, improving medical diagnosis and treatment. Yanning comes to ECE from the University of Electronic Science and Technology in China. Post graduation, she hopes to continue her research at a university or other institution.

 

Hari Cherupalli

Hari Cherupalli’s research interests are computer architecture, computer aided design, security, low power, embedded processors. His dissertation is titled, “Application-specific design and optimization for ultra low-power embedded systems,” and he is working under the guidance of Prof. John Sartori. His work opens up a new direction in application analysis of microprocessors, crossing multiple layers of design abstraction, from binary to processor layout. Such an analysis can lead to significant benefits in power, cost, and security of ultra low-power microprocessors that drive the Internet of Things revolution. One of the immediate benefits is that battery operated devices could last longer on the same battery. Yet another benefit is improved form factor of systems where area and cost are critical. Currently, Hari is working on commercializing his research, and has filed patents for his work. Hari comes to ECE from the Indian Institute of Technology, Kharagpur, where he earned his bachelor’s and master’s degrees in electrical engineering.

 

Ahmed Zamzam

Ahmed Zamzam’s research interests lie in monitoring, learning, and management for smart power grids. His dissertation is titled “Intelligent monitoring and control for next generation smart grids,” and he is working under the guidance of Prof. Nikos Sidiropoulos. His research contributes to the development of efficient monitoring and resource management tools in power systems. The overarching goal is to support more reliable and secure energy systems, and a greener environment. Ahmed enjoys the research process and environment and working with students. After graduation, he hopes to pursue his interests at a research university, or work as a scientist at a national laboratory. Prior to arriving at the University, Ahmed earned his bachelor’s degree from Cairo University, Egypt, and his master’s degree from Nile University, Egypt, both in electrical engineering.

 

Zhengyang Zhao

Zhengyang Zhao’s research interests lie in the development of novel spintronic devices and using them in advanced memory and computing applications. His work includes resolving fundamental challenges and improving the performance of spintronic devices, and expanding the range of applications enabled by novel devices. His dissertation is titled, “Development of spintronic devices for ultra-energy efficient non-volatile memory and logic applications,” and he is working under the guidance of Prof. Jian-Ping Wang. Zhengyang’s dissertation focuses on one of the most significant application of spintronics: magnetic random access memory (MRAM). MRAM uses the spin of electrons to store data and bears certain critical advantages: non-volatility, read/write speed comparable to that of DRAM, and an unlimited lifetime. Spin Hall effect (SHE), a recently discovered phenomenon, provides a new means of spin generation that allows MRAM to be faster and more energy efficient. However, there are gaps between basic SHE devices and SHE-based MRAM. Zhengyang’s research addresses these gaps, proposing different strategies along with experimental prototyping. He is also developing solutions to mitigate limitations that arise from the speed of the computer being constrained by the data transfer between memory and CPU. Zhengyang hopes to apply his expertise in industry after he graduates. Zhengyang comes to us from Xi’an Jiaotong University, China, where he earned his bachelor’s degree in electrical engineering.

To read about other graduate awards and honors, and their recipients, please check this link

 

Tin-Based Semiconductors Show Experimental Promise

University Scientists Report Breakthroughs in Stannate Semiconductors

In the world of semiconductors, silicon has reigned supreme for over half a century. It is the foundation of microprocessors and memory devices which are now ubiquitous entities deeply involved in most aspects of our lives, from running our smartphones to reminding us when our cars need an oil change. However, silicon does have some shortcomings: it is opaque to visible light, and does not handle high levels of power well. So, in recent years, scientists have been working to discover new semiconductors, such as gallium nitride (GaN), that can provide these additional capabilities. Currently, scientists at the University of Minnesota are developing a new class of semiconductors that could greatly expand the application range of semiconductor technology, and the essential component of this new material might come as a surprise: it is tin. The charge is being led by Prof. Steven Koester from the Department of Electrical and Computer Engineering, and Prof. Bharat Jalan from the Department of Chemical Engineering and Materials Science.

TIN POISED TO TAKE ON A NEW ROLE

Tin is the key element in a class of complex oxide semiconductors known as “stannate perovskites.” Perovskites are materials with the chemical formula ABO3, where, in the case of stannates, the “B” element is tin. Although perovskites are interesting from the point of view of physics and have a wide range of uses in other fields, they do not have many room temperature electronics applications. However, stannates are set to change this; their high electron mobility and wide band gap give them several remarkable properties: they are transparent to visible light, they can sustain extremely high voltages over tiny distances in the material, and most importantly, they are great electrical conductors.

As Prof. Jalan notes, “In most complex oxides, electron ‘mobility’, or how easily electrons can move, is very low at practical temperature.  However, stannates have much higher electrical mobility among all perovskite materials.”

Papers recently published by University research teams led by professors Koester and Jalan have generated considerable excitement and interest in the use of tin-based semiconductors as transistors, a vital component in electronic devices. In “Depletion Mode MOSFET Using La-Doped BaSnO as a Channel,” the team demonstrated the use of barium stannate (BaSnO3) as a channel material in a field-effect transistor (FET). Critically, this work also details the role of dislocations (which, very crudely explained, occur when a crystal with a particular spacing between the atoms is grown on top of another crystal with a different atomic spacing) in BaSnO3-based FETs. The results point to ways by which the performance of BaSnO3 channel devices can be enhanced.

SHIFTING FOCUS

Among the stannate-based perovskites, BaSnO3 has garnered most of the recent attention due to its high mobility and its ability to be doped, or made electrically conductive by adding additional elements. However, lately Koester’s and Jalan’s teams have turned the spotlight on strontium stannate (SrSnO3), and for good reasons.

Pointing to the difference between barium stannate and strontium stannate, Prof. Koester says, “Strontium stannate is a particularly interesting material because it has an even wider band gap than barium stannate and thus can support even higher voltages.”

Pushing ahead their research into perovskites, the scientists have  demonstrated a SrSnO3 FET, the first demonstration of a transistor using this material. The results are presented in the paper, “Demonstration of a Depletion-Mode SrSnO n-Channel MESFET,” published in IEEE Electron Device Letters. The demonstration was made possible after the Jalan team recently learned how to dope SrSnO3, also a first for this material.

THE STRONTIUM STANNATE ADVANTAGE

The larger band gap present in SrSnO allows for visible light transparency, and greater breakdown voltage. Strontium stannate is also easier to grow on commercially available substrates because of its better lattice matching, compared to BaSnO. According to Jalan, this affords lower dislocation density, which entails the possibility of greater reliability of, and improved power handling capability by, the device.

Strontium stannate is also easier to grow on commercially available substrates, because of its better lattice matching, compared to barium stannate.

Other characteristics of this compound also suggest that it displays electron mobilities close to BaSnO3 and existing wide-gap semiconductors. For Prof. Koester’s team, the results of the recent demonstration of a SrSnO3 FETs are promising. The device displayed gain values that are a record for a stannate-based perovskite FET, and five times better than existing strontium titanate (SrTiO3)-based devices. SrTiO3, a more well-known perovskite, and regarded as the silicon among perovskites, has very low mobility, making it a weak candidate for transistors. While it is a worthwhile contender for many other applications and fundamental studies, its low mobility has hindered its widespread deployment in microelectronics.

LOOKING AHEAD

Even though the current performance of the SrSnO3 FETs still lags behind that of prevailing state-of-the-art GaN FETs, the research team believes the true potential lies in new capabilities that cannot be achieved in GaN. Perhaps the most important capability is the ability to integrate epitaxial ferroelectrics. SrSnO3 is closely lattice matched to one of the best known ferroelectric materials, barium titanate, and this could lead to applications with critical potential such as reconfigurable high power electronic devices.  

Based on the outcomes of their latest work, the University’s research teams are hopeful that SrSnO3 can open the door to incorporating a wide range of new properties, including ferroelectrics, piezoelectrics, and many others.  These ‘smart materials’ could lead to new kinds of reconfigurable electronics with a vast range of applications from military radars, to cell phone towers, to autonomous vehicles.

This research is primarily supported by the Young Investigator Program of the Air Force Office of Scientific Research (AFOSR), and the National Science Foundation through  its Ceramics program (CER) and the University’s MRSEC.

You can learn more about Prof. Steven J. Koester’s pioneering work here, and check his research lab here

More information about Professor Jalan’s research can be found here. 

 

Spinning toward Advancements in Science and Technology

In a cross-departmental collaborative undertaking, scientists at the University of Minnesota have successfully grown a quantum material, bismuth selenide, by magnetron sputtering, a process compatible with large scale production, and currently in use commercially. The development bears significance for the semiconductor industry, holding the possibility of improved energy efficiency for computing and memory devices.

The details of the team’s research are reported in “Room-temperature high spin-orbit torque due to quantum confinement in sputtered BixSe(1-x) films,” published in Nature Materials.

TOPOLOGICAL MATERIALS AND SPIN-ORBIT TORQUES

The class of materials known as topological insulators (TI) has been of interest to scientists in the fields of physics and material science.  The unique property they possess–insulating interior and conducting surface–can improve the energy efficiency of post-CMOS computing devices, and magnetoresistive random access memory (MRAM), a non-volatile memory. TIs can convert charge into non-equilibrium spin density efficiently because of the perpendicular locking of an electron’s spin with its momentum. Such efficient conversion is critical to magnetoresistive random access memory (MRAM) and post-CMOS computing devices for faster writing of data, reduced power consumption, and greater device reliability.

Typically spin-polarized current is generated using a ferromagnetic polarizer which transfers its spin angular momentum to another ferromagnetic layer. This is the mechanism for the creation of spin-transfer torque (STT). However, the inefficiency of the ferromagnetic polarizer entails higher power consumption, and lower reliability. On the other hand, spin-orbit torque (SOT), an outcome of spin-orbit interaction, essential to the atomic structure of specific materials such as heavy metals (for instance, tungsten, W)  has advantages over STT. The absence of a separate polarizer gives SOT-based memory and logic devices an edge over STT-based devices in terms of energy efficiency and device reliability. Recently, topological materials have been reported to generate large spin-orbit torques. 

GROWING BISMUTH SELENIDE

However these developments can be worthwhile only if they can be nudged into the mainstream, and commercially viable processes for growing TI are developed. Typically, topological insulators are created either using a single crystal growth process, or a process called molecular beam epitaxy. Both of these techniques cannot be easily scaled up for use in the semiconductor industry. In the present study, researchers started with bismuth selenide (Bi₂Se₃), a compound of bismuth and selenium. They then used a thin film deposition technique called “sputtering,” which is driven by momentum exchange between the ions and atoms in the target materials due to collisions. While the sputtering technique is common in the semiconductor industry, this is the first time it has been used to create a topological insulator material. Significantly, this could be scaled up for semiconductor and magnetic industry applications. It is also worth noting that on testing the new material, researchers found it to be 18 times more efficient in computing processing and memory compared to current materials.

According to lead scientist, and Distinguished McKnight University Professor and Robert F. Hartmann Chair in Electrical Engineering Jian-Ping Wang, “The unique feature of the sputtered bismuth selenide is the presence of nano-sized grains, which were missing in molecular beam epitaxy grown single crystalline topological insulator films.” 

Prof. Tony Low, co-author of the paper and faculty in the Department of Electrical and Computer Engineering points out, “The nano-sized grains present in the sputtered bismuth selenide films yield higher spin-accumulation due to the spin momentum locking in the deeply located bands. As grains shrink, quantum confinement of the wave function further enhances spin-accumulation.”

Prof. Wang’s excitement is palpable, “Using the sputtering process to fabricate a quantum material like a bismuth-selenide-based topological insulator is against the intuitive instincts of all researchers in the field and actually is not supported by any existing theory. Four years ago, we started with a big idea to search for a practical pathway to grow and apply the topological insulator material for future computing and memory devices. Our surprising experimental discovery led to a new theory for topological insulator materials. Research is all about being patient and collaborating with team members. This time there was a big pay off,” Wang said.

THE ROAD AHEAD

With support from the Semiconductor Research Corporation, the researchers have filed for a materials-related patent, and experts in the semiconductor industry have requested samples of the material. The current paper represents the latest development in the research led by Prof. Wang, and collaborating scientists at the University of Minnesota and other institutions in the field of spintronics. His team has been at the forefront of the search for novel materials, and fabrication techniques that can enhance computation in semiconductor-based devices by improving storage and processing speeds, and the development of magnetic biomedical technologies and devices that can improve patient comfort and outcomes.

Recently, Prof. Wang as principal investigator received a $3.1 million grant from DARPA (Defence Advanced Research Projects Agency) under the Electronics Resurgence Initiative (ERI) for exploring novel materials and circuit structures that can take us beyond the limitations imposed by Moore’s Law, and meet looming engineering, economic, and defense challenges.

Another notable example of the pioneering work conducted by Prof. Wang’s research team is the development of Z-Lab, a portable diagnostic platform designed to perform on site testing of biological samples for various ailments. This is the first version of the prototype developed for point-of-care diagnostics. The details of the device and results of the test are reported in the paper “Portable GMR Handheld Platform for the Detection of Influenza A Virus” published recently in ACS Sensors.

Earlier in the year, a collaborative effort led by researchers at the University resulting in the experimental discovery of ferromagnetic properties in Ruthenium was published in Nature Communications under the title, “Demonstration of Ru as the 4th ferromagnetic element at room temperature. The discovery makes it the fourth single element with such properties in the periodic table. It opens an exciting new chapter in the fundamental studies of this element, and its application potential in the creation and scaling of magnetic memories, and breaking new ground in computing performance.

Late last year, Prof. Wang and his team in collaboration with researchers from Pennsylvania State University discovered the existence of magnetoresistance in topological insulator-ferromagnetic bilayers. This discovery has significant implications for the semiconductor industry, and opens up the door to enabling low power computing, brain-like computing, and chips for robots in the near future. The details of their research are published in Nature Communications under the title “Unidirectional spin-Hall and Rashba−Edelstein magnetoresistance in topological insulator-ferromagnet layer heterostructures.” The study confirms the existence of such unidirectional magnetoresistance and reveals that the adoption of TI, compared to heavy metals, improves the magnetoresistance performance by about twice at a temperature of 150 Kelvin (-123.15 Celsius).

Prof. Wang and his team of scientists are on an exciting path, unpacking and harnessing the potential of spinning electrons, translating it into applications disparate but critical to diverse aspects of our lives: low power computing, memory devices, biomedical devices. Translating these research outcomes into technologies that are adopted by industry, and impact our lives is only a matter of time. Our lives will certainly look different as these research outcomes make their way to industry and become commercially available.

 

The research for the paper, “Room-temperature high spin-orbit torque due to quantum confinement in sputtered BixSe(1-x) films,” was funded by the Center for Spintronic Materials, Interfaces and Novel Architectures (C-SPIN) at the University of Minnesota. C-SPIN is a Semiconductor Research Corporation program sponsored by the Microelectronics Advanced Research Corp. (MARCO) and the Defense Advanced Research Projects Agency (DARPA). C-SPIN is led by Prof. Wang.

Check the University’s coverage of Prof. Wang’s latest research here

Check the AAAS EurekAlert here