Nav: Home

Squeezed nanocrystals: A new model predicts their shape when blanketed under graphene

April 05, 2019

In a collaboration between the U.S. Department of Energy's Ames Laboratory and Northeastern University, scientists have developed a model for predicting the shape of metal nanocrystals or "islands" sandwiched between or below two-dimensional (2D) materials such as graphene. The advance moves 2D quantum materials a step closer to applications in electronics.

Ames Laboratory scientist are experts in 2D materials, and recently discovered a first-of-its-kind copper and graphite combination, produced by depositing copper on ion-bombarded graphite at high temperature and in an ultra-high vacuum environment. This produced a distribution of copper islands, embedded under an ultra-thin "blanket" consisting of a few layers of graphene.

"Because these metal islands can potentially serve as electrical contacts or heat sinks in electronic applications, their shape and how they reach that shape are important pieces of information in controlling the design and synthesis of these materials," said Pat Thiel, an Ames Laboratory scientist and Distinguished Professor of Chemistry and Materials Science and Engineering at Iowa State University.

Ames Laboratory scientists used scanning tunneling microscopy to painstakingly measure the shapes of more than a hundred nanometer-scale copper islands. This provided the experimental basis for a theoretical model developed jointly by researchers at Northeastern University's Department of Mechanical and Industrial Engineering and at Ames Laboratory. The model served to explain the data extremely well. The one exception, concerning copper islands less than 10 nm tall, will be the basis for further research.

"We love to see our physics applied, and this was a beautiful way to apply it," said Scott E. Julien, Ph.D. candidate, at Northeastern. "We were able to model the elastic response of the graphene as it drapes over the copper islands, and use it to predict the shapes of the islands."

The work showed that the top layer of graphene resists the upward pressure exerted by the growing metal island. In effect, the graphene layer squeezes downward and flattens the copper islands. Accounting for these effects as well as other key energetics leads to the unanticipated prediction of a universal, or size-independent, shape of the islands, at least for sufficiently-large islands of a given metal.

"This principle should work with other metals and other layered materials as well," said Research Assistant, Ann Lii-Rosales. "Experimentally we want to see if we can use the same recipe to synthesize metals under other types of layered materials with predictable results."
The research is further discussed in the paper, "Squeezed Nanocrystals: Equilibrium Configuration of Metal Clusters Embedded Beneath the Surface of a Layered Material," authored by Scott E. Julien, Ann Lii-Rosales, Kai-Tak Wan, Yong Han, Michael C. Tringides, James W. Evans, and Patricia A. Thiel; and published in Nanoscale.

The research was a collaboration between Ames Laboratory and Northeastern University.

Work at Northeastern University was supported by the National Institute of Standards and Technology (NIST), a national facility operated under the U.S. Department of Commerce.

Work at Ames Laboratory was supported primarily by the U.S. Department of Energy Office of Science. This work was also supported in part by a grant of computer time at the National Energy Research Scientific Computing Centre (NERSC), a DOE Office of Science User Facility.

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.

DOE's 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:

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.
Graphene is 3D as well as 2D
Graphene is actually a 3D material as well as a 2D material, according to a new study from Queen Mary University of London.
How to purify water with graphene
Scientists from the National University of Science and Technology 'MISIS' together with their colleagues from Derzhavin Tambov State University and Saratov Chernyshevsky State University have figured out that graphene is capable of purifying water, making it drinkable, without further chlorination.
Decoupled graphene thanks to potassium bromide
The use of potassium bromide in the production of graphene on a copper surface can lead to better results.
1 + 1 does not equal 2 for graphene-like 2D materials
Physicists from the University of Sheffield have discovered that when two atomically thin graphene-like materials are placed on top of each other their properties change, and a material with novel hybrid properties emerges, paving the way for design of new materials and nano-devices.
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

Climate Mindset
In the past few months, human beings have come together to fight a global threat. This hour, TED speakers explore how our response can be the catalyst to fight another global crisis: climate change. Guests include political strategist Tom Rivett-Carnac, diplomat Christiana Figueres, climate justice activist Xiye Bastida, and writer, illustrator, and artist Oliver Jeffers.
Now Playing: Science for the People

#562 Superbug to Bedside
By now we're all good and scared about antibiotic resistance, one of the many things coming to get us all. But there's good news, sort of. News antibiotics are coming out! How do they get tested? What does that kind of a trial look like and how does it happen? Host Bethany Brookeshire talks with Matt McCarthy, author of "Superbugs: The Race to Stop an Epidemic", about the ins and outs of testing a new antibiotic in the hospital.
Now Playing: Radiolab

Speedy Beet
There are few musical moments more well-worn than the first four notes of Beethoven's Fifth Symphony. But in this short, we find out that Beethoven might have made a last-ditch effort to keep his music from ever feeling familiar, to keep pushing his listeners to a kind of psychological limit. Big thanks to our Brooklyn Philharmonic musicians: Deborah Buck and Suzy Perelman on violin, Arash Amini on cello, and Ah Ling Neu on viola. And check out The First Four Notes, Matthew Guerrieri's book on Beethoven's Fifth. Support Radiolab today at