Researchers from the Department of Physics and the Swiss Nanoscience Institute at the University of Basel, working in collaboration with the University of Bern, have recently produced and studied a compound referred to as "kagome graphene", that consists of a regular pattern of hexagons and equilateral triangles that surround one another. The name kagome comes from the old Japanese art of kagome weaving, in which baskets are woven in the same pattern.
The team's measurements have reportedly delivered promising results that point to unusual electrical or magnetic properties of the material.
To produce the kagome graphene, the team applied a precursor 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 the same 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 Dr. Rémy Pawlak, first author of the study. With microscopes of this kind, researchers can 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 doing so, the researchers observed that electrons of a defined energy, which is 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 Professor Ernst Meyer, who leads the group in which the projects were carried out. "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. In this way, kagome graphene differs significantly from graphene, whose conductivity cannot be switched on and off as easily.
The team plans to continue to investigate the material by detaching the kagome lattice from its metallic substrate and studying 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. In the future, kagome graphene could act as a key building block in sustainable and efficient electronic components," says Ernst Meyer.