Kagome graphene is characterized by a regular lattice of hexagons and triangles. It behaves as a semiconductor and may also have unusual electrical properties. Image: R. Pawlak, Department of Physics, University of Basel.Researchers around the world are searching for new synthetic materials with special properties such as superconductivity — that is, conducting electric current without resistance. These new substances are an important step in the development of highly energy-efficient electronics, and the starting material is often graphene, a single-layer of carbon atoms in a honeycomb pattern.
In addition to conventional graphene, however, there is also 'kagome graphene', which theoretical calculations predict should have completely different properties to graphene. Kagome graphene consists of a regular pattern of hexagons and equilateral triangles that surround one another. The name 'kagome' comes from Japanese and refers to the old Japanese art of kagome weaving, in which baskets were woven with this pattern.
Now, for the first time, researchers from the Department of Physics and the Swiss Nanoscience Institute at the University of Basel, working in collaboration with researchers at the University of Bern in Switzerland, have produced and studied kagome graphene. The researchers’ measurements, which they report in a paper in Angewandte Chemie, have delivered promising results that point to this material possessing unusual electrical or magnetic properties.
To produce the kagome graphene, the team applied a carbon-containing precursor compound to a silver substrate by vapor deposition and then heated it to form an organometallic intermediate on the metal surface. Further heating produced kagome graphene, which is made up exclusively of carbon and nitrogen atoms and features a regular pattern of hexagons and triangles.
"We used scanning tunneling and atomic force microscopes to study the structural and electronic properties of the kagome lattice," reports Rémy Pawlak, first author of the paper. With these microscopes, researchers are able to probe the structural and electrical properties of materials using a tiny tip – in this case, the tip was terminated with individual carbon monoxide molecules.
In so doing, Pawlak and his colleagues observed that electrons with a defined energy, which can be selected by applying an electrical voltage, are 'trapped' between the triangles that appear in the crystal lattice of kagome graphene. This behavior clearly distinguishes the material from conventional graphene, where electrons are distributed across various energy states in the lattice – in other words, they are delocalized.
"The localization observed in kagome graphene is desirable and precisely what we were looking for," explains Ernst Meyer, who leads the group that conducted the work. "It causes strong interactions between the electrons – and, in turn, these interactions provide the basis for unusual phenomena, such as conduction without resistance."
The analyses also revealed that kagome graphene features semiconducting properties – in other words, its conducting properties can be switched on or off, as with a transistor. Once again, this shows that kagome graphene differs significantly from conventional graphene, whose conductivity cannot be switched on and off as easily.
In subsequent investigations, the team will detach the kagome lattice from its metallic substrate and study its electronic properties further. “The flat band structure identified in the experiments supports the theoretical calculations, which predict that exciting electronic and magnetic phenomena could occur in kagome lattices," says Meyer. "In the future, kagome graphene could act as a key building block in sustainable and efficient electronic components."
This story is adapted from material from the University of Basel, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.