New synthesis method for 2D material produces unexpected result

A new two-dimensional (2D) material has become a reality, thanks to a team of Danish and Italian scientists. The team, led by physicists at Aarhus University in Denmark, has succeeded in the first experimental realization and structural investigation of single-layer vanadium disulphide (VS₂), which is reported in a paper in 2D Materials.

VS₂ is one of a diverse group of compounds known as transition metal dichalcogenides (TMDs). Many of these assume a layered crystal structure from which atomically thin crystalline sheets can be isolated. The electronic properties of these single-atomic-layer crystals can differ in important ways from those of the layered bulk crystals.

"Theoretical studies suggest that single-layer VS₂ might exhibit very interesting physics, including magnetism and strong correlations," explained Charlotte Sanders at Aarhus University. "It might also host charge density wave states, as does bulk VS₂. However, making VS₂ is difficult and the single layer has not been successfully made before now.

"In fact, magnetism in single-layer materials has only recently been observed, and is still quite rare. So, the possibility that this material might be magnetic is exciting."

"Theoretical studies suggest that single-layer VS2 might exhibit very interesting physics, including magnetism and strong correlations. It might also host charge density wave states, as does bulk VS2. However, making VS2 is difficult and the single layer has not been successfully made before now."Charlotte Sanders, Aarhus University

To make the single layer of VS₂, the researchers evaporated vanadium onto a clean gold surface at room temperature. They then heated the sample in the presence of sulphur-containing molecules that react with the vanadium to produce VS₂. The team measured the properties of the samples using low-energy electron diffraction, scanning tunneling microscopy and X-ray photoelectron spectroscopy.

Significantly, the team also discovered a new and unpredicted vanadium sulphide compound. Most 2D materials can in theory (although not necessarily in practice) be derived from bulk layered crystals. However, there is no three-dimensional material with a similar stoichiometry and crystal structure to those of the new compound, which is formed when single-layer VS₂ is depleted of sulphur by heating.

In consideration of the likely magnetic properties of related vanadium compounds, the new material might be another candidate for 2D magnetism. "The new material's electronic structure, along with possible charge density wave phases and magnetic ordering, remain to be explored, and an interesting open question is how its properties differ from those of stoichiometric single-layer VS₂," said Sanders.

This story is adapted from material from IOP Publishing, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.