“Bite” defects revealed in bottom-up graphene nanoribbons

Two recent studies by a collaborative team of scientists from two NCCR MARVEL labs have identified a new type of defect as the most common source of disorder in on-surface synthesized graphene nanoribbons (GNRs).

Combining scanning probe microscopy with first-principles calculations allowed the researchers to identify the atomic structure of these so-called "bite" defects and to investigate their effect on quantum electronic transport in two different types of graphene nanoribbon. They also established guidelines for minimizing the detrimental impact of these defects on electronic transport and proposed defective zigzag-edged nanoribbons as suitable platforms for certain applications in spintronics.

Researchers design atomically precise graphene nanoribbon heterojunction sensor

An international research team, led by the University of Cologne, has succeeded in connecting several atomically precise graphene nanoribbons to form complex structures. The scientists have synthesized and spectroscopically characterized nanoribbon heterojunctions, and were able to integrate the heterojunctions into an electronic component. In this way, they have created a novel sensor that is highly sensitive to atoms and molecules.

"The graphene nanoribbon heterojunctions used to make the sensor are each seven and fourteen carbon atoms wide and about 50 nanometres long. What makes them special is that their edges are free of defects. This is why they are called "atomically precise" nanoribbons," explained Dr. Boris Senkovskiy from the Institute for Experimental Physics. The researchers connected several of these nanoribbon heterojunctions at their short ends, thus creating more complex heterostructures that act as tunneling barriers.

New method to produce graphene nanoribbons could promote use in telecommunications applications

University of Wisconsin–Madison researchers have fabricated graphene into the smallest ribbon structures to date, using a method that is said to make scaling-up simple. In tests with these tiny ribbons, the scientists discovered they were closing in on the properties they needed to move graphene toward usefulness in telecommunications equipment.

Flexible, easy-to-scale nanoribbons move graphene toward use in tech applications imageImage credit: University of Wisconsin−Madison

“Previous research suggested that to be viable for telecommunication technologies, graphene would need to be structured prohibitively small over large areas, (which is) a fabrication nightmare,” says Joel Siegel, a UW–Madison graduate student in physics professor Victor Brar’s group and co-lead author of the study. “In our study, we created a scalable fabrication technique to make the smallest graphene ribbon structures yet and found that with modest further reductions in ribbon width, we can start getting to telecommunications range.”

Researchers design method that makes graphene nanoribbons easier to produce

Russian researchers have proposed a new method for synthesizing high-quality graphene nanoribbons. The team's approach to chemical vapor deposition offers a higher yield at a lower cost, compared with the currently used nanoribbon self-assembly on noble metal substrates.

Two nanoribbon edge configurations imageTwo nanoribbon edge configurations. The pink network of carbon atoms is a ribbon with zigzag (Z) edges, and the yellow one has so-called armchair (A) edges. Image credit MIPT

Unlike silicon, graphene does not have the ability to switch between a conductive and a nonconductive state. This defining characteristic of semiconductors is crucial for creating transistors, which are the basis for all of electronics. However, once you cut graphene into narrow ribbons, they gain semiconducting properties, provided that the edges have the right geometry and there are no structural defects. Such nanoribbons have already been used in experimental transistors with reasonably good characteristics, and the material’s elasticity means the devices can be made flexible. While it is technologically challenging to integrate 2D materials with 3D electronics, there are no fundamental reasons why nanoribbons could not replace silicon.

Graphene nano-ribbons could help build future integrated circuits

University of California researchers, along with teams from other U.S-based institutions like Columbia University, Lawrence Berkeley National Laboratory and University of Washington, have created a metallic wire made entirely of carbon, setting the stage for a ramp-up in research to build carbon-based transistors and, ultimately, computers.

"Staying within the same material, within the realm of carbon-based materials, is what brings this technology together now," said Felix Fischer, UC Berkeley professor of chemistry, noting that the ability to make all circuit elements from the same material makes fabrication easier. "That has been one of the key things that has been missing in the big picture of an all-carbon-based integrated circuit architecture."