Physicists and chemists have produced a highly sensitive sensor / This is made possible by a new type of heterostructure made from “atomically precise” graphene nanostructures / Publication in Nature Communications
An international research team headed by the University of Cologne has succeeded for the first time in connecting several “atomically precise” nanostrips made of graphene, a modification of carbon, to form complex structures. The scientists were able to integrate the strips into an electronic component. In this way, they have created a new type of sensor that is highly sensitive to atoms and molecules. The results of their research are published under the title “Tunneling current modulation in atomically precise graphene nanoribbon heterojunctions” in the renowned journal Nature Communications. This work was created in close cooperation between the II. Physikalisches Institut, the Department of Chemistry at the University of Cologne and research groups from Montreal, Novosibirsk
The graphene nanostrips are only one nanometer – a millionth of a millimeter – wide. Graphene consists of only a single layer of carbon atoms and is considered to be the thinnest material in the world. In 2010 researchers from Manchester succeeded in producing monatomic layers of graphene for the first time, for which they received the Nobel Prize. “The graphene nano-strips used to manufacture the sensor are each between seven and fourteen carbon atoms wide and around 50 nanometers long. The special thing is that their edges are free of defects. They are therefore referred to as ‘atomically precise’ nanostrips, ”explains Dr. Boris Senkovskiy from the 2nd Physics Institute at the University of Cologne. The researchers have now succeeded to connect several of these strips with their short end and thus create more complex heterostructures. These heterostructures have properties of semiconductors.
The heterostructures were examined by means of angle-resolved photoemission, optical spectroscopy and scanning tunneling microscopy. In the next step, the generated heterostructures were integrated into an electronic component. The electrical current that flows through the nanorestrip heterostructure is determined by the quantum mechanical tunnel effect. This states that under certain conditions electrons can overcome existing energy barriers in atoms by “tunneling”, so that a current flow then occurs, although the barrier is higher than the available energy of the electron.
The researchers have succeeded in building a new type of sensor for the adsorption of atoms and molecules from the nanorestrip heterostructure. The tunnel current through the heterostructure is particularly sensitive to adsorbates that accumulate on surfaces. This means that the current strength changes when atoms or molecules, for example from gases, accumulate on the surface of the sensor. “The sensor prototype we built has excellent properties. Among other things, it is particularly sensitive and can be used to measure even the smallest amounts of adsorbate, ”says Professor Dr. Alexander Grüneis, head of a working group at the 2nd Physics Institute.
Featured image: Schematic illustration of the aligned GNR heterojunctions integrated into the device. Lateral fusion of 7-AGNRs leads to the formation of quasi-metallic 14-AGNR and 21-AGNRs. When the source–drain contacts are fabricated, the remaining 7-AGNR segments act as tunneling barriers. Red arrows indicate different paths for charge transport © authors
Nat. Commun. 12, 2542 (2021),
Provided by University of Cologne