Graphene grains come in several different shapes. Hydrogen gas controls the grains' appearance.
OAK RIDGE, US: A new approach to growing graphene greatly reduces problems that have plagued researchers in the past and clears a path to the crystalline form of graphite’s use in sophisticated electronic devices of tomorrow.
Findings of researchers at the Department of Energy’s Oak Ridge National Laboratory demonstrate that hydrogen rather than carbon dictates the graphene grain shape and size, according to a team led by ORNL’s Ivan Vlassiouk, a Eugene Wigner Fellow and Sergei Smirnov, a Professor of Chemistry at New Mexico State University. This research is published in ACS Nano.
“Hydrogen not only initiates the graphene growth, but controls the graphene shape and size. In our paper, we have described a method to grow well-defined graphene grains that have perfect hexagonal shapes pointing to the faultless single crystal structure,” said Vlassiouk.
In the past two years, graphene growth has involved the decomposition of carbon-containing gases such as methane on a copper foil under high temperatures, the so-called chemical vapour deposition method.
“We have shown that, surprisingly, it is not only the carbon source and the substrate that dictate the growth rate, the shape and size of the graphene grain,” said Vlassiouk. “We found that hydrogen, which was thought to play a rather passive role, is crucial for graphene growth as well. It contributes to both the activation of adsorbed molecules that initiate the growth of graphene and to the elimination of weak bonds at the grain edges that control the quality of the graphene.”
Using their new recipe, Vlassiouk and colleagues have created a way to reliably synthesize graphene on a large scale. The fact that their technique allows them to control grain size and boundaries may result in improved functionality of the material in transistors, semiconductors and potentially hundreds of electronic devices.
“Our findings are crucial for developing a method for growing ultra-large-scale single domain graphene that will constitute a major breakthrough toward graphene implementation in real-world devices,” said Vlassiouk.
Other authors of the paper, “Role of Hydrogen in Chemical Vapour Deposition Growth of Large Single-Crystal Graphene,” are Murari Regmi, Pasquale Fulvio, Sheng Dai, Panos Datskos and Gyula Eres of ORNL.
The research was supported by the Department of Energy’s Office of Science, in part through the Fluid Interface Reactions, Structures and Transport Centre, a DOE Energy Frontier Research Centre led by ORNL. A portion of the work was performed at the Centre for Nanophase Materials Sciences, one of the five DOE Nanoscale Science Research Centres supported by the DOE Office of Science.
(C) Oak Ridge National Laboratory News