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All-Carbon, Spintronic Design Proposal Could Pave Way for Smaller, Better Performing Electronic Structures

A novel computing system made exclusively from carbon was designed by a Researcher with the Erik Jonsson School of Engineering and Computer Science at UT Dallas. This system might one day replace the silicon transistors that power existing electronic devices.

Dr. Joseph S. Friedman (credit: UT Dallas)

“The concept brings together an assortment of existing nanoscale technologies and combines them in a new way,” said Dr. Joseph S. Friedman, Assistant Professor of Electrical and Computer Engineering at UT Dallas who conducted most of the research while he was a Doctoral Student at Northwestern University.

The resulting all-carbon spin logic proposal is a computing system that Friedman believes could certainly be made smaller than silicon transistors, with increased performance. The research paper by lead Author Friedman and a number of collaborators has been published in the June 5th edition of the online journal Nature Communications.

Current electronic devices are run by transistors, which are miniature silicon structures that depend on negatively charged electrons traveling through the silicon, forming an electric current. Transistors act like switches, switching current on and off.

Besides transporting a charge, electrons possess another property called spin, which refers to their magnetic properties. In recent years, Engineers have been examining ways to exploit the spin features of electrons to form a new class of transistors and devices called “spintronics.”

Friedman’s all-carbon, spintronic switch works as a logic gate that depends upon a standard tenet of electromagnetics: As electric current travels through a wire, it forms a magnetic field that wraps around the wire. Furthermore, a magnetic field near a 2D ribbon of carbon — known as a graphene nanoribbon — influences the current flowing through the ribbon. Traditionally, silicon-based computers, transistors cannot make use of this phenomenon. Instead, they are linked to each other by wires. The output from one transistor is linked by a wire to the input for the next transistor and so on in a flowing manner.

In Friedman’s spintronic circuit design, electrons traveling via carbon nanotubes — fundamentally miniature wires made up of carbon — form a magnetic field that influences the flow of current in an adjacent graphene nanoribbon, providing cascaded logic gates that are not physically linked.

Since the communication between each of the graphene nanoribbons happens via an electromagnetic wave, instead of the physical movement of electrons, Friedman anticipates that communication will be a lot faster, with the potential for terahertz clock speeds. Moreover, these carbon materials can be formed smaller than silicon-based transistors, which are nearing their maximum size due to silicon’s narrow material properties.

This was a great interdisciplinary collaborative team effort, combining my circuit proposal with physics analysis by Jean-Pierre Leburton and Anuj Girdhar at the University of Illinois at Urbana-Champaign; technology guidance from Ryan Gelfand at the University of Central Florida; and systems insight from Alan Sahakian, Allen Taflove, Bruce Wessels, Hooman Mohseni and Gokhan Memik at Northwestern.

Dr. Joseph S. Friedman, Assistant Professor of Electrical and Computer Engineering, UT Dallas

Although the concept is still theoretical, Friedman said progress toward a prototype of the all-carbon, cascaded spintronic computing system will continue in the interdisciplinary NanoSpinCompute research laboratory, which he heads at UT Dallas.

Girdhar’s Beckman Graduate Fellowship supports this research.

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