Researchers Develop Graphene Ribbons That Behave Like Semiconductors

July 19, 2020 by Luke James

A team of researchers has produced what they call the first porous graphene ribbons with properties that make them attractive for electronics applications.

As we all know, graphene is a revolutionary material consisting of a single layer of carbon atoms arranged in a honeycomb lattice.

Since its discovery, it has been a material of great interest because of its properties, making it useful for a broad range of potential next-gen applications, including several in electronics. These properties include excellent electrical conductivity as well as high strength and rigidity. 

Today, research teams worldwide are working around the clock to build on these characteristics by substituting the carbon atoms in graphene's crystal lattice with atoms of different elements.

Professor Ernst Meyer leads one of these teams at the University of Basel, which, along with colleagues from the University of Bern, claim to have succeeded in producing the world's first graphene ribbons whose crystal lattice contains both periodic pores and a regular pattern of nitrogen atoms. 

A Ladder Structure

The team's material structure takes the form of a ladder, with each rung on this "ladder" containing two atoms of nitrogen. The researchers heated the individual building blocks in a step-by-step process on a silver surface in a vacuum to synthesize these porous, nitrogen-containing graphene ribbons. 

It is only when temperatures hit 220°C that graphene ribbons are formed. By using atomic force microscopy, the researchers were able to monitor the individual steps in the synthesis of the material and confirm the perfect ladder structure and its stability.


Individual building blocks heated on a silver surface to synthesize graphene ribbon.

Individual building blocks are heated on a silver surface in order to synthesize a porous graphene ribbon that exhibits semiconducting properties and a ladder-like structure, in each rung of the ladder, two carbon atoms have been replaced with nitrogen atoms (blue). Image credited to University of Basel


Semiconductor-Like Behavior

Furthermore, through scanning tunneling microscopy, the research team also demonstrated that their new graphene ribbons were no longer electrical conductors like pure graphene, but rather that they behaved as semiconductors. These findings were confirmed by researchers at the University of Bern and the University of Warwick through additional theoretical calculations of the electronic properties. 

"The semiconducting properties are essential for the potential applications in electronics, as their conductivity can be adjusted specifically," said Dr. Rémy Pawlak. 

And although further research is yet to be carried out, we know that a high concentration of nitrogen atoms in the crystal lattice causes the graphene ribbons to magnetize when exposed to a magnetic field.

"We expect these porous, nitrogen-doped graphene ribbons to display extraordinary magnetic properties," says Ernst Meyer. Thus, it is thought that the ribbons could be of interest for potential applications in the field of quantum computing.