The molecular structure of the new 2D material made from silicon, boron and nitrogen. Image: Madhu Menon.A new one atom-thick material could upstage the wonder material graphene and advance computing technology, say the scientists who discovered it. Reported in Physical Review B, the new two-dimensional (2D) material is made up of silicon, boron and nitrogen, which are all light, inexpensive and abundant elements, and is extremely stable, a property many other graphene alternatives lack.
"We used simulations to see if the bonds would break or disintegrate – it didn't happen," said Madhu Menon, a physicist in the Center for Computational Sciences at the University of Kentucky, who helped discover the material. "We heated the material up to 1000°C and it still didn't break." Menon discovered that material in collaboration with scientists from Daimler in Germany and the Institute for Electronic Structure and Laser (IESL) in Greece.
Using state-of-the-art theoretical computations, Menon and his collaborators demonstrated that silicon, boron and nitrogen can be combined to produce a one atom-thick material with properties that can be fine-tuned for applications beyond the abilities of graphene. The bulk of these theoretical computations were performed on computers at the Center for Computational Sciences.
While graphene is touted as being the world's strongest material with many unique properties, it has one downside: it isn't a semiconductor. The search for 2D materials with semiconducting properties has led researchers to a new class of three-layer materials called transition-metal dichalcogenides (TMDCs). Most TMDCs are semiconductors and can be made into digital processors that are more efficient than those made with silicon. However, TMDCs are much bulkier than graphene and made of substances that are not necessarily abundant or inexpensive.
Searching for new 2D materials made from substances that are light, abundant, inexpensive and semiconducting, Menon and his colleagues studied different combinations of elements from the first and second row of the Periodic Table. Although there are many ways to combine silicon, boron and nitrogen to form planar structures, the team’s computations revealed that only one specific arrangement of these elements resulted in a stable structure. This arrangement follows the same hexagonal pattern as graphene, but that is where the similarity ends.
The three elements forming the new material all have different sizes; the bonds connecting the atoms are also different. As a result, the sides of the hexagons formed by these atoms are unequal, unlike in graphene. The new material is metallic, but can easily be made semiconducting by attaching other elements on top of the silicon atoms.
The presence of silicon also offers the exciting possibility of a seamless integration with current silicon-based computing technology, allowing the industry to slowly move away from silicon instead of replacing it entirely. What is more, attaching other elements to the 2D material not only creates the electronic band gap that confers semiconducting properties, but can also selectively change the band gap values – a key advantage over graphene for solar energy conversion and electronics applications.
"We know that silicon-based technology is reaching its limit because we are putting more and more components together and making electronic processors more and more compact," Menon said. "But we know that this cannot go on indefinitely; we need smarter materials."
Other graphene-like materials have been proposed but lack the strength of the material discovered by Menon and his team. Silicene, for example, a 2D version of silicon, does not have a flat surface and eventually forms a 3D surface. Other materials are highly unstable, only lasting for a few hours at most.
Menon and his team are now working in close collaboration with a team led by Mahendra Sunkara in the Conn Center for Renewable Energy Research at the University of Louisville to create this material in the lab. The Conn Center team has already collaborated with Menon on a number of new materials systems, testing his theory with experiments for several new solar materials.
"We are very anxious for this to be made in the lab," Menon said. "The ultimate test of any theory is experimental verification, so the sooner the better!"
Some of the proposed properties of this new 2D material, such as the ability to form various types of nanotubes, are discussed in the paper but Menon expects more to emerge with further study. "This discovery opens a new chapter in material science by offering new opportunities for researchers to explore functional flexibility and new properties for new applications," he said. "We can expect some surprises."
This story is adapted from material from the University of Kentucky, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.