Graphene Could Be Great for Spintronics

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Illustration: M. Venkata Kamalakar/Nature Communications

Graphene did not immediately impress anybody with its potential in the field of spintronics, the use of the spin of electrons to encode information rather than charge. If you laid graphene out flat, it didn’t appear to influence electron spin,  that property remained random rather than patterned. But that all changed when scientists saw what happens when you put a small bend in the graphene.

Since then, there’s been a steady stream of research looking at the capabilities of graphene in spintronic applications.  The latest, and perhaps most significant development, is news that researchers at Chalmers University of Technology in Sweden have been able to preserve electron spin for an extended distance using large area graphene.

"We believe that these results will attract a lot of attention in the research community and put graphene on the map for applications in spintronic components," said Saroj Dash, one of the Chalmers researchers, in a press release.

Typically, the spin of electrons in a material is a fragile and short-lived affair. In the most common spintronic application, the read heads for hard drives, that short life span doesn’t pose a problem because the information that the spin imparts only needs to travel a few nanometers. However, if you could extend the spin over a greater distance, you would have a greater opportunity to use it for transmitting information.

"In future spin-based components, it is expected that the electrons must be able to travel several tens of micrometers with their spins kept aligned. Metals, such as aluminum or copper, do not have the capacity to handle this,”said Saroj Dash. “Graphene appears to be the only possible material at the moment.”

In work published in the journal Nature Communications, the Chalmers researchers were able to demonstrate precise pure spin transport over lengths of 16 micrometers with a spin lifetime of 1.2 nanoseconds. According to the research paper, these spin parameters are “six times higher than previous reports and highest at room temperature for any form of pristine graphene on industrial standard [silicon/silicon-dioxide] substrates.”

What may be the most encouraging bit of this research is that the Chalmers team was able to use graphene produced through chemical vapor deposition (CVD) to achieve this result. CVD techniques promise a way of producing graphene in bulk and  consequently more cheaply than the so-called “Scotch Tape” method in which graphene is pulled off of bulk graphite in single-layer flakes.

Also, the long-term impact of this development may mean an end to the albatross that graphene has worn around its neck: the lack of an inherent band gap.

"Graphene is a good conductor and has no band gaps. But in spintronics there is no need for band gaps to switch between on and off, one and zero. This is controlled instead by the electron's up or down spin orientations," explained Dash.

Recent insight about graphene’s ability to transport electrons long distances without resistance (ballistic transport) promised a new era in electronics.  It seems now that graphene’s ability to maintain an electron spin over a greater distance will also change the way we approach electronics.

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Nanoclast

IEEE Spectrum’s nanotechnology blog, featuring news and analysis about the development, applications, and future of science and technology at the nanoscale.

 
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