Creating perfect edges in 2D-materials

October 19, 2020

Ultrathin materials such as graphene promise a revolution in nanoscience and technology. Researchers at Chalmers University of Technology, Sweden, have now made an important advance within the field. In a recent paper in Nature Communications they present a method for controlling the edges of two-dimensional materials using a 'magic' chemical.

"Our method makes it possible to control the edges - atom by atom - in a way that is both easy and scalable, using only mild heating together with abundant, environmentally friendly chemicals, such as hydrogen peroxide," says Battulga Munkhbat, a postdoctoral researcher at the Department of Physics at Chalmers University of Technology, and first author of the paper.

Materials as thin as just a single atomic layer are known as two-dimensional, or 2D, materials. The most well-known example is graphene, as well as molybdenum disulphide, its semiconductor analogue. Future developments within the field could benefit from studying one particular characteristic inherent to such materials - their edges. Controlling the edges is a challenging scientific problem, because they are very different in comparison to the main body of a 2D material. For example, a specific type of edge found in transition metal dichalcogenides (known as TMD's, such as the aforementioned molybdenum disulphide), can have magnetic and catalytic properties.

Typical TMD materials have edges which can exist in two distinct variants, known as zigzag or armchair. These alternatives are so different that their physical and chemical properties are not at all alike. For instance, calculations predict that zigzag edges are metallic and ferromagnetic, whereas armchair edges are semiconducting and non-magnetic. Similar to these remarkable variations in physical properties, one could expect that chemical properties of zigzag and armchair edges are also very different. If so, it could be possible that certain chemicals might 'dissolve' armchair edges, while leaving zigzag ones unaffected.

Now, such a 'magic' chemical is exactly what the Chalmers researchers have found - in the form of ordinary hydrogen peroxide. At first, the researchers were completely surprised by the new results.

"It was not only that one type of edge was dominant over the others, but also that the resulting edges were extremely sharp - nearly atomically sharp. This indicates that the 'magic' chemical operates in a so-called self-limiting manner, removing unwanted material atom-by-atom, eventually resulting in edges at the atomically sharp limit. The resulting patterns followed the crystallographic orientation of the original TMD material, producing beautiful, atomically sharp hexagonal nanostructures," says Battulga Munkhbat.

"An extremely fascinating development"

The new method, which includes a combination of standard top-down lithographic methods with a new anisotropic wet etching process, therefore makes it possible to create perfect edges in two-dimensional materials.

"This method opens up new and unprecedented possibilities for van der Waals materials (layered 2D materials). We can now combine edge physics with 2D physics in one single material. It is an extremely fascinating development," says Timur Shegai, Associate Professor at the Department of Physics at Chalmers and leader of the research project.

These and other related materials often attract significant research attention, as they enable crucial advances within in nanoscience and technology, with potential applications ranging from quantum electronics to new types of nano-devices. These hopes are manifested in the Graphene Flagship, Europe's biggest ever research initiative, which is coordinated by Chalmers University of Technology.

To make the new technology available to research laboratories and high-tech companies, the researchers have founded a start-up company that offers high quality atomically sharp TMD materials. The researchers also plan to further develop applications for these atomically sharp metamaterials.
-end-
More on the publication

The paper "Transition metal dichalcogenide metamaterials with atomic precision" recently appeared in Nature Communications. The article is written by Battulga Munkhbat, Andrew Yankovich, Denis Baranov, Ruggero Verre, Eva Olsson and Timur Shegai at the Department of Physics at Chalmers.

For more information, please contact:

Battulga Munkhbat, Post Doc
Department of Physics
Chalmers University of Technology, Sweden
+46 73 995 34 79
battulga@chalmers.se

Timur Shegai, Associate Professor
Department of Physics, Chalmers University of Technology, Sweden
+46 31 772 31 23
timurs@chalmers.se

Chalmers University of Technology

Related Graphene Articles from Brightsurf:

How to stack graphene up to four layers
IBS research team reports a novel method to grow multi-layered, single-crystalline graphene with a selected stacking order in a wafer scale.

Graphene-Adsorbate van der Waals bonding memory inspires 'smart' graphene sensors
Electric field modulation of the graphene-adsorbate interaction induces unique van der Waals (vdW) bonding which were previously assumed to be randomized by thermal energy after the electric field is turned off.

Graphene: It is all about the toppings
The way graphene interacts with other materials depends on how these materials are brought into contact with the graphene.

Discovery of graphene switch
Researchers at Japan Advanced Institute of Science and Technology (JAIST) successfully developed the special in-situ transmission electron microscope technique to measure the current-voltage curve of graphene nanoribbon (GNR) with observing the edge structure and found that the electrical conductance of narrow GNRs with a zigzag edge structure abruptly increased above the critical bias voltage, indicating that which they are expected to be applied to switching devices, which are the smallest in the world.

New 'brick' for nanotechnology: Graphene Nanomesh
Researchers at Japan advanced institute of science and technology (JAIST) successfully fabricated suspended graphene nanomesh (GNM) by using the focused helium ion beam technology.

Flatter graphene, faster electrons
Scientists from the Swiss Nanoscience Institute and the Department of Physics at the University of Basel developed a technique to flatten corrugations in graphene layers.

Graphene Flagship publishes handbook of graphene manufacturing
The EU-funded research project Graphene Flagship has published a comprehensive guide explaining how to produce and process graphene and related materials (GRMs).

How to induce magnetism in graphene
Graphene, a two-dimensional structure made of carbon, is a material with excellent mechani-cal, electronic and optical properties.

Graphene: The more you bend it, the softer it gets
New research by engineers at the University of Illinois combines atomic-scale experimentation with computer modeling to determine how much energy it takes to bend multilayer graphene -- a question that has eluded scientists since graphene was first isolated.

How do you know it's perfect graphene?
Scientists at the US Department of Energy's Ames Laboratory have discovered an indicator that reliably demonstrates a sample's high quality, and it was one that was hiding in plain sight for decades.

Read More: Graphene News and Graphene Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.