Jun 24, 2019 | Updated: 04:51 PM EDT

A New Model Can Predict the Shape of a Squeezed Nanocrystal When Blanketed Under Graphene

Apr 06, 2019 04:18 PM EDT

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This research has moved 2-D quantum materials just one step closer to application of nanocrystal in electronics. 

Ames Laboratory scientist are experts in 2-D materials, and they have discovered just recently a copper and graphite combination, that is considered as first of its kind, and it is produced by depositing the copper on the ion-bombarded graphite at a specific high temperature and in an environment with ultra-high vacuum. This then produced copper islands that are embedded under a blanket that is ultra-thin and that consists of 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.

The scientists from Ames Laboratory used microscopy to measure the shapes of hundred nanometer-scale copper islands painstakingly. This then provided them the basis for their experiment and a theoretical model that is developed by the joint efforts of the researchers from Northeastern University's Department of Mechanical and Industrial Engineering and Ames Laboratory. The model made was able to explain the data well. The exception though is that the copper islands that are less than 10 nm tall are kept as the basis for their 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."

This work showed that the top part of the graphene layer resists the pressure exerted upward by the metal island that is growing. In effect to this, the graphene layer squeezes downward and it also flattens the copper islands. Based on these effects and the other key energetics that leads to the prediction of a size-dependent shape of the islands 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," published in Nanoscale.

Thi research was a collaboration between Northeastern University and Ames Laboratory 

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