How Perfect Can Graphene Be?

Oct 13, 2009 By Lisa Zyga feature
Higher quality samples of graphene are important for exploring the realistic limits of its electronic properties, as well as verifying predictions about graphene’s quantum properties. Image credit: Wikimedia Commons.

(PhysOrg.com) -- Physicists have investigated the purest graphene to date, and have found that the material possesses unprecedented high electronic quality. The discovery has raised the bar for this relatively new material, and challenges scientists to find out just how perfect graphene can be.

The team of scientists, Petr Neugebauer, et al, from the Grenoble High Magnetic Field Laboratory in France, has published its study in a recent issue of Physical Review Letters, called “How Perfect Can Be?” The scientists found that their naturally occurring graphene sample possessed a carrier mobility almost two orders of magnitude higher than other types of graphene, and a scattering time that significantly exceeds those reported in any man-made graphene samples. Both properties could open the doors for future developments in graphene technologies.

“The main finding of our paper is definitely the discovery that there exists graphene of exceptionally high quality in nature, much better than man-made specimens prepared by any of current methods, either by exfoliation of bulk or epitaxial growth,” coauthor Milan Orlita told PhysOrg.com. “The question for the current technology is thus no longer whether the quality of today’s specimens can be significantly increased, but instead, how to do it. And it is just the quality of specimens which is, as believed by many researchers, limiting further progress in the physics of graphene.”

Experimentally realized for the first time in 2004, graphene consists of a one-atom-thick sheet of arranged in a hexagonal honeycomb lattice, giving it the appearance of chicken wire. Graphene is the basic building block of several other carbon allotropes: for example, graphene sheets stacked together create graphite; rolled up, they make carbon nanotubes; and rolled into a sphere, they become buckyballs. Therefore, finding a more perfect form of graphene could have important implications for many areas of nanotechnology and materials science.

As the physicists explain in their study, there has been a good deal of research in exploring the quantum electrodynamics properties of graphene. However, further progress seems to be limited by the insufficient electronic quality of man-made graphene structures. In addition, graphene’s substrate and other surrounding mediums tend to degrade the electronic quality of graphene samples. Higher quality samples are crucial for exploring the realistic limits and quantum phenomena in graphene.

In a study published earlier this year in Physical Review Letters, another team of scientists discovered a form of graphene composed of well-defined graphene flakes in the form of sheets located on - yet decoupled from - the surface of bulk graphite (Li, et al.). Not only is this graphene well-structured, but the underlying graphite also serves as a well-matched substrate for investigating the graphene layer, which is what the Grenoble scientists do in the current study.

As the scientists explain, the physical mechanism behind the pure graphene’s good electronic properties is due to its quantum characteristics - in particular, its well-defined quantization. In experiments, the scientists found that the graphene’s Dirac-like electronic states are quantized in magnetic fields down to 1 milliTesla, and they expect the quantization to survive as low as 1 microTesla.

The new measurements of graphene’s extremely high carrier mobility set new and surprisingly high limits for graphene’s potential properties. The physicists hope that the question of how perfect graphene can be will have an ultimate answer that bodes well for further developments of graphene technologies, although Orlita noted that applications may not come for a while.

“In my opinion, we are still relatively far from real applications of graphene and most of current work on graphene is driven by the fundamental interest,” he said. “Nevertheless, just the fundamental research is calling for higher quality samples, as there is a number of phenomena predicted theoretically (e.g. related to the quantum electrodynamics on Dirac fermions), which are still to be experimentally confirmed.”

More information: P. Neugebauer, M. Orlita, C. Faugeras, A.-L. Barra, M. Potemski. “How Perfect Can Graphene Be?” . 103, 136403 (2009). DOI: 10.1103/PhysRevLett.103.136403

Copyright 2009 PhysOrg.com.
All rights reserved. This material may not be published, broadcast, rewritten or redistributed in whole or part without the express written permission of PhysOrg.com.

Explore further: Nano filter cleans environmentally hazardous industrial byproducts

add to favorites email to friend print save as pdf

Related Stories

Could Graphene Replace Semiconductors?

Sep 08, 2008

(PhysOrg.com) -- “People want a faster computer chip,” Philip Kim tells PhysOrg.com. “And it needs to be smaller. But in order to increase the speed of the chip, or to get it smaller, we are approaching a point where ...

A Smarter Way to Grow Graphene

May 14, 2008

Graphene, a sheet of carbon just one atom thick, has many potential uses in the electronics industry, but producing these ideal two-dimensional carbon sheets is very difficult and, as a result, their use has ...

Light-speed nanotech: Controlling the nature of graphene

Jan 21, 2009

Researchers at Rensselaer Polytechnic Institute have discovered a new method for controlling the nature of graphene, bringing academia and industry potentially one step closer to realizing the mass production ...

A new type of spin valve that uses graphene

Jul 09, 2007

“Some people think that graphene, a form of carbon, is the material of the future,” Allen Goldman tells PhysOrg.com. “It’s of high scientific interest because of its unusual electronic properties.”

Recommended for you

User comments : 4

Adjust slider to filter visible comments by rank

Display comments: newest first

Alizee
Oct 13, 2009
This comment has been removed by a moderator.
googleplex
1 / 5 (3) Oct 13, 2009
I heard that pencil graphite contains graphene. Perhaps they should look at that.
TJ_alberta
not rated yet Oct 13, 2009
"the underlying graphite also serves as a well-matched substrate..." so what other crystals that are readily available in pure form could be a graphene substrate?
otto1923
not rated yet Oct 13, 2009
@googleplex
Would it also hold true that pens contain graphene in liquid form and could this be considered another form of this common material which researchers failed to discover even after they had buckyballs to twiddle for 40 years or so?
Husky
5 / 5 (1) Oct 13, 2009
Most graphene sheets, although one layer thick are not completely flat, but contain ripples as outlet for stressforces created by the honecomb connection, now what would be interesting to know is , what is the "flatness" of these superior samples mentioned in the article?

They don't necessarely have to be flatter, but it could also be that the rippling is more uniform in size and direction, forced at the time of creation , depending on the graphite substrate.

More uniform rippling in size/vector, i would suspect, quantum mechanical effect to run more in sync, so perhaps the way to go is not to aim for flat, but deliberately row graphene on nanostamped prerippled substrates or a strained substrate or a warm substrate that is allowed to cool down and while shrinking compressive forces induce ripples in the attached layer?

This might have happened when the natural graphite was subjected to heat and pressure in the earth mantle and gradually cooling down

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.