Amorphous single layer carbon film

NUS researchers have synthesised single layers of amorphous carbon films for potential industrial applications.

Amorphous materials are used widely in many applications but detailed scientific understanding of their atomic arrangement remains poor. A research team led by Prof Barbaros ÖZYILMAZ from Department of Physics, Department of Materials Science and Engineering and Centre for Advanced 2D Materials (CA2DM), NUS has synthesised for the first time, monolayer amorphous carbon (MAC) which is a sheet of one atom thick amorphous carbon film, using laser-assisted chemical vapour deposition. This breakthrough allows for direct imaging to reveal how atoms are arranged in amorphous materials.

In the study of amorphous materials, there are two opposing groups. One says that it is possible for materials to have a fully-disordered, completely random structure. The other says there is always nanometre-sized order, of tiny crystallites, that is surrounded by random disorder.

The newly synthesised MAC films show the latter arrangement. The researchers see nanometre-sized patches of strained and distorted hexagonal carbon rings, but there is random disorder between these patches. Hence, the MAC films also contain five-, seven-, and eight-membered rings, too.

The NUS team grew the material and studied its properties and potential areas of application. In addition, atomic resolution imaging was performed by the group of Prof Kazu Suenaga from the National Institute of Advanced Industrial Science and Technology (AIST), Japan, and Prof Junhao Lin from Southern University of Science and Technology (SUSTECH), China. Furthermore, theoretical simulations were carried out by the group of Prof Sokrates Pantelides from Vanderbilt University, USA.

The MAC exhibits certain properties that are totally different from traditional monolayer materials. MAC films can be “plastically deformed”, meaning that they can be can be stretched into irregular shapes, and stay conformed to that position. Compared to nanometre-thick crystalline materials, which would easily snap when stretched, MAC has the potential to expand its use in a number of industrial applications.

“MAC is much more hardy and cheaper to make than conventional crystalline two-dimensional materials. The laser-assisted deposition process through which MAC is synthesised is commonly used in industry. Hence, we can grow a large-area, defect-free, monolayer film on a wide variety of substrates with high throughput and at low temperature,” explained Prof Özyilmaz.

Researchers at NUS Physics, CA2DM and Materials Science and Engineering have created the world’s first atomically thin amorphous carbon film. The amorphous structure have widely varying atom-to-atom distance unlike crystals. This is because of the random arrangement of five-, six-, seven- and eight-carbon rings in a planar carbon network, leading to a wide distribution of bond lengths (in Å) and bond angles. [Credit: Nature]

Reference

Toh CT; Zhang H; Lin J; Mayorov AS; Wang YP; Orofeo CM; Ferry DB; Andersen H; Kakenov N; Guo Z; Abidi IH; Sims H; Suenaga K; Pantelides ST; Özyilmaz B*, “Synthesis and properties of free-standing monolayer amorphous carbon” NATURE DOI: 10.1038/s41586-019-1871-2 Published: 2020.