For the first time, American scientists synthesize graphene nanoribbons atomically one after another on metal—a coaxial hexagon of graphene grown in a furnace. According to a study published in the latest issue of the American Chemical Society, this graphene "onion ring" is expected to be used in lithium-ion batteries and advanced electronic devices.
James Tur, a physicist at Rice University, one of the leaders of the research, said that, in general, graphene grown in a furnace by chemical vapor deposition is a seed (a little dust on the surface of copper or other metal). Or a bump) begins. In the nucleation process, a carbon atom attaches to the surface of the seed. Other carbon atoms “perhaps gourd scoops†form a wire-like mesh.
The Tours team conducted some experiments to find out how graphene grew the first ring under high pressure and in a hydrogen-rich environment. They found that in this environment, a piece of fast-growing graphene flakes was hydrogenated and its entire edge became a nucleation site. This edge places carbon atoms under the skin of the graphene, where the carbon atoms begin to form a new sheet. But because the top graphene grows fast, it will eventually stop the carbon atoms from flowing to the new thin layer underneath it, stopping the growth of graphene at the bottom, leaving a graphene ring. The whole process will continue to repeat the cycle.
Tour explains: "This mechanism relies on the topmost graphene layer to prevent carbon atoms from reaching the bottom. Finally, what we get is a laminated multilayer single-crystal graphene 'onion ring."
Tours said: "In general, if we continue to cut a large object, you can get nanobelts. But if we can start from scratch, we can grow nanobelts, we can control the edges, and the edge of the atomic structure will help To determine the electrical properties of graphene, the edges of the hexagonal graphene 'onion ring' we obtained are all sawtooth-shaped, which gives us the properties of the metal, and we can change the relationship between hydrogen and carbon in the growth environment. The relative pressure results in a completely new structure that is very different from ordinary graphene.†After further testing, it was found that the microrings were formed at the bottom but not at the top of the sheet, and the top graphene sheet could be removed using argon plasma, leaving an independent ring. .
The width of this ring is between 10 nanometers and 450 nanometers, and the width will also affect the electrical properties. Therefore, finding the method to control the width becomes the scientist's next goal. Tour said: "If we can produce 10 nanometer wide graphene ribbons uniformly, we can turn it into a low-voltage transistor. This transistor may be suitable for the manufacture of advanced lithium-ion battery lithium storage devices. "(Reporter Liu Xia)
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