Nav: Home

How do you know it's perfect graphene?

October 30, 2019

Producing structurally perfect graphene and other 2D materials is the secret to tapping into their potential novel electronic and spintronic properties. But how do we know when graphene, the most widely studied 2D material, is perfect-- a defect-free and uniform layer of atoms?

Scientists at the U.S. Department of Energy's Ames Laboratory have discovered an indicator that reliably demonstrates a sample's high quality, and it was one that was hiding in plain sight for decades.

The researchers were investigating samples of graphene using low energy electron diffraction, a technique commonly used in physics to study the crystal structure of the surfaces of solid materials.

What they found didn't follow the accepted rules of diffraction.

"The discovery is a paradox," said Michael Tringides, a senior scientist at Ames Laboratory who investigates the unique properties of 2D materials and metals grown on graphene, graphite, and other carbon coated surfaces. "Textbook diffraction states that the more flawless a material is, the sharper and clearer the diffraction spots, and imperfect materials have low intensity, broader diffraction spots."

But in the case of highly uniform samples of graphene, the diffraction studies not only showed the expected sharp spots, but also a very broad band of diffuse diffraction in the background.

"That result is not intuitive and very strange," said Tringides, "but we find this broad diffraction pattern to be an intrinsic feature to graphene, and when you have it, you have very good graphene. This is a good way to quantitatively measure its structural perfection."

What's more, this strange diffraction pattern was present and visible in the last 25 years of graphene research publications, and yet ignored. "It was a big, noticeable phenomena, and reproducible, and we realized it must be extremely important in some way," said Tringides.

While more theoretical work is needed to fully explain the experimental findings, the scientists believe the broad diffraction phenomenon is caused by the confinement of graphene electrons within a single layer of atoms. According to the fundamentals of quantum mechanics, because the electron position normal to the layer is precisely known, their wave vector must have a spread, which is transferred to the diffracted electrons. This effect is significant for other types of 2D materials as well. With the continued and growing interest in 2D materials for a variety of applications, improving their structural quality will be the key to promising new technologies, said Tringides.

"This work provides an important step towards the ability to optimize graphene and other 2D materials precisely, and tailor their properties for specific applications," he said.

The research is further discussed in the paper, "Diffraction paradox: An unusually broad diffraction background marks high quality graphene," authored by S. Chen, M. Horn von Hoegen, P. A. Thiel, and M. C. Tringides; and published in Physical Review B.

Ames Laboratory is a U.S. Department of Energy Office of Science National Laboratory operated by Iowa State University. Ames Laboratory creates innovative materials, technologies and energy solutions. We use our expertise, unique capabilities and interdisciplinary collaborations to solve global problems.
Ames Laboratory is supported by the Office of Science of the U.S. Department of Energy. The Office of Science is the single largest supporter of basic research in the physical sciences in the United States, and is working to address some of the most pressing challenges of our time. For more information, please visit

DOE/Ames Laboratory

Related Graphene Articles:

How to stack graphene up to four layers
IBS research team reports a novel method to grow multi-layered, single-crystalline graphene with a selected stacking order in a wafer scale.
Graphene-Adsorbate van der Waals bonding memory inspires 'smart' graphene sensors
Electric field modulation of the graphene-adsorbate interaction induces unique van der Waals (vdW) bonding which were previously assumed to be randomized by thermal energy after the electric field is turned off.
Graphene: It is all about the toppings
The way graphene interacts with other materials depends on how these materials are brought into contact with the graphene.
Discovery of graphene switch
Researchers at Japan Advanced Institute of Science and Technology (JAIST) successfully developed the special in-situ transmission electron microscope technique to measure the current-voltage curve of graphene nanoribbon (GNR) with observing the edge structure and found that the electrical conductance of narrow GNRs with a zigzag edge structure abruptly increased above the critical bias voltage, indicating that which they are expected to be applied to switching devices, which are the smallest in the world.
New 'brick' for nanotechnology: Graphene Nanomesh
Researchers at Japan advanced institute of science and technology (JAIST) successfully fabricated suspended graphene nanomesh (GNM) by using the focused helium ion beam technology.
Flatter graphene, faster electrons
Scientists from the Swiss Nanoscience Institute and the Department of Physics at the University of Basel developed a technique to flatten corrugations in graphene layers.
Graphene Flagship publishes handbook of graphene manufacturing
The EU-funded research project Graphene Flagship has published a comprehensive guide explaining how to produce and process graphene and related materials (GRMs).
How to induce magnetism in graphene
Graphene, a two-dimensional structure made of carbon, is a material with excellent mechani-cal, electronic and optical properties.
Graphene: The more you bend it, the softer it gets
New research by engineers at the University of Illinois combines atomic-scale experimentation with computer modeling to determine how much energy it takes to bend multilayer graphene -- a question that has eluded scientists since graphene was first isolated.
How do you know it's perfect graphene?
Scientists at the US Department of Energy's Ames Laboratory have discovered an indicator that reliably demonstrates a sample's high quality, and it was one that was hiding in plain sight for decades.
More Graphene News and Graphene Current Events

Trending Science News

Current Coronavirus (COVID-19) News

Top Science Podcasts

We have hand picked the top science podcasts of 2020.
Now Playing: TED Radio Hour

Warped Reality
False information on the internet makes it harder and harder to know what's true, and the consequences have been devastating. This hour, TED speakers explore ideas around technology and deception. Guests include law professor Danielle Citron, journalist Andrew Marantz, and computer scientist Joy Buolamwini.
Now Playing: Science for the People

#576 Science Communication in Creative Places
When you think of science communication, you might think of TED talks or museum talks or video talks, or... people giving lectures. It's a lot of people talking. But there's more to sci comm than that. This week host Bethany Brookshire talks to three people who have looked at science communication in places you might not expect it. We'll speak with Mauna Dasari, a graduate student at Notre Dame, about making mammals into a March Madness match. We'll talk with Sarah Garner, director of the Pathologists Assistant Program at Tulane University School of Medicine, who takes pathology instruction out of...
Now Playing: Radiolab

How to Win Friends and Influence Baboons
Baboon troops. We all know they're hierarchical. There's the big brutish alpha male who rules with a hairy iron fist, and then there's everybody else. Which is what Meg Crofoot thought too, before she used GPS collars to track the movements of a troop of baboons for a whole month. What she and her team learned from this data gave them a whole new understanding of baboon troop dynamics, and, moment to moment, who really has the power.  This episode was reported and produced by Annie McEwen. Support Radiolab by becoming a member today at