An international team of researchers, led by the University of Bern and the National Physical Laboratory (NPL) and assisted by the University of the Basque Country (UPV/EHU, Spain) and Chuo University (Japan), has demonstrated a new way to control the functionality of next-gen molecular electronic devices using graphene. The results could be used to develop smaller, higher-performance devices for use in a applications like sensors, flexible electronics, energy conversion and storage, and more.

The team demonstrated the stability of multi-layer graphene-based molecular electronic devices down to the single molecule limit. The findings represent a major step change in the development of graphene-based molecular electronics, with the reproducible properties of covalent contacts between molecules and graphene (even at room temperature) reportedly overcoming the limitations of current state-of-the-art technologies based on coinage metals.

The team explains that adsorption of specific molecules on graphene-based electronic devices allows device functionality to be tuned, mainly by modifying its electrical resistance. However, it is difficult to relate overall device properties to the properties of the individual molecules adsorbed, since averaged quantities cannot identify possibly large variations across the graphene’s surface.

The team performed measurements of the electric current flowing though single molecules attached to graphite or multi-layered graphene electrodes using a unique low-noise experimental technique, which allowed the scientists to resolve these molecule-to-molecule variations. They demonstrated that variations on the graphite surface are very small and that the nature of the chemical contact of a molecule to the top graphene layer dictates the functionality of single-molecule electronic devices.

"We find that by carefully designing the chemical contact of molecules to graphene-based materials, we can tune their functionality," said the team. "Our single-molecule diodes showed that the rectification direction of electric current can be indeed switched by changing the nature of chemical contact of each molecule", the researchers added.

"We are confident that our findings represent a significant step towards the practical exploitation of molecular electronic devices, and we expect a significant change in the research field direction following our path of room-temperature stable chemical bonding," summarized a team member. The findings will also help researchers working in electro-catalysis and energy conversion research design graphene/molecule interfaces in their experimental systems to improve the efficiency of the catalyst or device.