Cheng Gong’s Super-Performance Energy-Efficient Devices (SPEED) featured in Nature Electronics

A recent paper by UMD Professor Cheng Gong (ECE, QTC), along with his students (first and second authors Shanchuan Liang and Ti Xie) and collaborators, has been published in the 2023 March issue of Nature Electronics. Titled “Small-voltage multiferroic control of two-dimensional magnetic insulators”, the paper focuses on two-dimensional (2D) multiferroics, in which electrical order and magnetic order couple mutually, thereby allowing electrical means to control magnetism. Gong experimentally discovered the first 2D magnet in 2017 (Nature, 2017) and shortly afterwards he theoretically predicted the heterostructure 2D multiferroics in 2019 (Nature Communications, 2019), as a postdoc at UC Berkeley. Recently, his team at UMD has taken big strides under this vision by developing super-performance 2D ferroelectric devices (Matter, 2022) and energy-efficient ferroelectric control of 2D magnets (i.e., heterostructure multiferroics; Nature Electronics 2023).

There is a clear logic flow underlying Gong’s work in these years. Magnetic materials are foundations of magnetoresistive memories and spintronic logic devices. Since Gong’s seminal discovery of 2D magnets, the next question in this rising field comes naturally about how to electrically control 2D magnetism. Such an electrical control directly interfaces the magnetism with electronics. Just within 2018, one year after the discovery of 2D magnet, there have been at least five research papers in top journals on electrical control of 2D magnet. “All these previous electrical controls were volatile”, Gong clarified.

In the recent Nature Electronics article, Gong’s team reported the first “non-volatile” electrical control of 2D magnets. The non-volatility means when electrical voltage is turned off, the information remains. “Non-volatile memories have been used in our daily life by billions of people in the world. Every time you restart your cell phone or computer, information remains there. With such non-volatility, the information will not evaporate with electrical shutdown.” Gong explained, “such a common and powerful non-volatile electrical effect has not been realized in 2D magnets before. Our fantastic students did it!” The key device component for this non-volatility is a ferroelectric material in contact with 2D magnets. “Ferroelectric materials are interesting. You can imagine a material, in which the center of positively charged ions and the center of negatively charged ions are not at the same position. Then, you can use an electrical voltage to switch the positions of positive and negative ions. Once they are switched, they will stay there even after the voltage is withdrawn. We use the non-volatility of ferroelectric materials to control 2D magnets”.

Once such non-volatile control is realized, people will be concerned about how much voltage is needed for such electrical operation. Basically, people care about energy consumption. When a ferroelectric material is thin and the electric field needed for the ferroelectric switching is not high, a small voltage for ferroelectric switching is possible. In this Nature Electronics article, Gong’s team demonstrated a modest 5 V voltage control of 2D magnet. “This small voltage means energy efficiency.” Gong explained.

“My collaborator Prof. Jian-Ping Wang coined SPEED to represent super-performance energy-efficient devices,” Gong remarked, “I love this acronym, which accurately summarizes the strengths of the two devices we developed recently”. In the 2022 December issue of Matter, Gong published the work on another interesting device: 2D materials based ferroelectric tunnel junction. This device exhibits a record-high ON/OFF ratio of 50,000,000,000 at room temperature, at least 10,000 times higher than the best of conventional oxide materials based ferroelectric memories. “Record-high ON/OFF ratio is super performance,” Gong added, “now these two devices perfectly explained SPEED – record-high ON/OFF ratio is Super Performance, and small voltage operation is Energy Efficient”.

“Prof. Gong’s work on these two facets really aim at hard core challenges the microelectronic industry has been confronted with for decades in the race for super-performance energy-efficient devices (SPEED)”, remarked Jian-Ping Wang, the Distinguished McKnight University Professor and Robert F. Hartmann Chair of the Department of Electrical and Computer Engineering, University of Minnesota. Wang is the co-author of both Nature Electronics and Matter publications. “I should highlight that, both devices in these two papers are non-volatile. The ferroelectric tunnel junction is on electronics and the heterostructure multiferroics is on spintronics.” Wang continued, “I look forward to further validating and applying those SPEED devices in the non-volatile memories and in-memory computing systems”.

“The exciting work of the Gong group closely aligns with the recently enacted U.S. CHIPS and Science Act, which allots significant funding for semiconductor R&D and manufacturing, including the prioritization of microelectronics research in nanoscale devices for better performance and lower energy consumption,” remarked UMD Professor and QTC Founding Director Ronald Walsworth. “Prof. Gong’s research beautifully connects the fundamental physics of quantum materials to potentially practical industry-favored devices.”

These newly developed devices and device concepts may serve as platforms for more technology innovations at large. Don Woodbury, Director of Innovation and Partnerships, Clark School of Engineering at University of Maryland, says “The 2D magnetoelectric devices developed in the Gong group represent state-of-the-art innovations of magnetoelectric devices in ultracompact footprint. These innovations have significant potential for integrated logic, memory and sensor devices that could have promising applications in defense, civilian, and commercial domains.”

Prof. Sennur Ulukus, the Chair of Department of Electrical and Computer Engineering, University of Maryland, summarized, “The original research in the Gong group lies exactly at the intersection of quantum materials and microelectronic devices, resonating with the recent quantum information science legislation and CHIPS and Science Act. Gong’s high-profile research achievements featured by the prestigious journals are a successful reflection of UMD’s quantum and microelectronic workforce.”

The research work published in this Nature Electronics article is primarily supported by the grants from the Air Force Office of Scientific Research under award no. FA9550-22-1-0349, Naval Air Warfare Center Aircraft Division under award no. N00421-22-1-0001, Army Research Laboratory under cooperative agreement no. W911NF-19-2-0181, National Science Foundation under award nos. CMMI-2233592 and 49100423C0011, and Northrop Grumman Mission Systems’ University Research Program.

Published April 17, 2023