Nat. Electron. Single atomically precise graphene nanoribbon enables quantum transport

Nat. Electron. Single atomically precise graphene nanoribbon enables quantum transport

The research results were published on August 14 in Nature Electronics under the title "Contacting individual graphene nanoribbons using carbon nanotube electrodes".

Empa researchers and their international collaborators have succeeded in attaching carbon nanotube electrodes to individual nanoribbons with atomic-level precision.

This is exactly what Mickael Perrin's team utilized in their work: for several years now, scientists at the Laboratory for Nanofacial Transport at the Swiss Federal Institute for Materials Testing and Development (EMPA), led by Michel Calame, have been carrying out research on graphene nanoribbons," explains Perrin. are even more fascinating than graphene itself. By varying the length and width of graphene nanoribbons, the shape of their edges, and by adding other atoms, it is possible to give them a variety of electrical, magnetic, and optical properties."

Studying the promising strips (ribbons) is no easy task. The narrower the ribbons, the more pronounced their quantum properties, but also the more difficult it is to obtain individual ribbons at the same time. This is necessary to understand the unique properties and possible applications of such quantum materials and to distinguish them from collective effects.

In this new study, Perrin, along with researcher Jian Zhang Zhang and an international team, succeeded for the first time in contacting a single long, atomically precise graphene nanoribbon. jian Zhang explains, "Graphene nanoribbons, which are only nine carbon atoms wide, are only 1 nanometer wide." To ensure that only one nanoribbon was touched, the researchers used a similarly sized electrode: the carbon nanotubes they used were also only 1 nanometer in diameter.

For such a delicate experiment, precision is key. It starts with the source material. The researchers obtained the graphene nanoribbons through a long and close collaboration with a laboratory led by Roman Fasel. Roman Fasel and his team have a long history of working with graphene nanoribbons, and were able to synthesize many different types of graphene nanoribbons from a single precursor molecule with atomic precision, Perrin said. molecules came from the Max Planck Institute for Polymer Research in Mainz."

As is often required to drive technological advances, interdisciplinarity is key, and different international research groups are involved, each with their own expertise: the carbon nanotubes were bred by a research group at Peking University, and to interpret the results, Empa researchers collaborated with computational scientists at the University of Warwick.

The experiments, in which the nanotubes came into contact with individual ribbons of carbon, posed a considerable challenge for the researchers. "The carbon nanotubes and graphene nanoribbons were grown on separate substrates. First, the nanotubes needed to be transferred to the device substrate and contacted with metal electrodes. Then, we cut them with high-resolution electron beam lithography to split them into two electrodes. Finally, we transfer the nanoribbon onto the same substrate. Precision is key: even the slightest rotation of the substrate greatly reduces the probability of successful contact." Perrin said, "Having access to the high-quality infrastructure at the Binnig and Roehl Nanotechnology Center (BRNC) at IBM Research was critical to testing and implementing this technology."

Multi-gate 9-AGNR transistor with single-walled carbon nanotube (SWNT) electrodes; Graphene nanoribbons (GNRs) are a class of tunable quantum materials.

Quantum transport through individual GNRs in contact with SWNT electrodes

Electronic and phononic properties of 9-AGNRs

The scientists confirmed the success of the experiment through charge transport measurements.

Perrin explains, "Since quantum effects are usually more pronounced at low temperatures, we performed the measurements in a high vacuum near absolute zero." But he is quick to add another particularly promising property of graphene nanoribbons: "Due to the extremely small size of these nanoribbons, we expect that their quantum effects will be so strong that they can be observed even at room temperature. This will allow us to design and run chips that actively exploit quantum effects without the need for complex cooling infrastructure."

Hatef Sadeghi, Professor at the University of Warwick, who is involved in the project, added: "This project enables the realization of individual nanoribbon devices that not only allow for the study of fundamental quantum effects such as the way electrons and phonons behave on the nanoscale, but also for the exploitation of such effects in applications such as quantum switching, quantum sensing and quantum energy conversion. "

However,, the graphene nanoribbons are not yet ready for commercial applications and there is still a lot of research to be done. In follow-up research, Zhang and Perrin aim to manipulate different quantum states on individual nanoribbons. In addition, they plan to create devices based on two nanoribbons connected in series to form double quantum dots: such circuits could serve as the smallest unit of information in a quantum computer - the quantum bit.

Mickael L. Perrin explores graphene nanoribbons in his lab.

In addition, Perrin was recently awarded a Starting Grant from the European Research Council (ERC) and a Sccellenza Professorial Fellowship from the Swiss National Science Foundation (SNSF), where he plans to use nanoribbons as efficient energy converters. In his inaugural lecture at ETH Zurich, he depicted a world in which we could generate electricity from temperature differences while losing almost no heat; this would be a real qualitative leap forward.

Reference link:

[1]https://www.empa.ch/web/s604/quantum-dot-generator

[2]https://www.eurekalert.org/news-releases/998584

[3]https://www.nature.com/articles/s41928-023-00991-3

[4]https://www.nature.com/articles/s41928-023-00992-2

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