Loops (seen above in blue) between graphene layers can be minimized using electron irradiation (bottom). (Credit: ORNL)

According to a press release, researchers at Oak Ridge National Lab have discovered how loops develop in graphene, an electrically conductive high-strength low-weight material that resembles an atomic-scale honeycomb. The nanoscale simulations are bringing scientists closer to using graphene in electronic applications.

“Graphene is a rising star in the materials world, given its potential for use in precise electronic components like transistors or other semiconductors,” says Bobby Sumpter, a staff scientist at ORNL.

Structural loops that sometimes form during a graphene cleaning process can render the material unsuitable for electronic applications.

However, when graphene was subjected to electron irradiation with a transmission electron microscope, it  prevented loop formation. The simulations showed that by injecting electrons to collect an image, the electrons were simultaneously changing the material’s structure.

“Taking a picture with a TEM is not merely taking a picture,” Sumpter says. “You might modify the picture at the same time that you’re looking at it.”

Graphene is only as good as the uniformity or cleanliness of its edges, which determine how effectively the material can transmit electrons. ORNL’s Vincent Meunier says the ability to efficiently clean graphene edges is crucial to using the material in electronics.

Recent experimental studies have shown that the Joule heating process can lead to undesirable loops that connect different graphene layers. Joule heating cleans graphene edges by running a current through the material. The team can show electron irradiation from a TEM prevents loop formation.