Catch-22 solved in molecular devices based on graphene

The conductivity of graphene has made it a target for many researchers seeking to exploit it to create devices at the molecular level. Today, a research team jointly led by the University of Warwick and EMPA has found a solution to the frustrating problem of stability and reproducibility. these graphene-based junctions were either mechanically stable or electrically stable, but not both at the same time.

Graphene and graphene molecules are an attractive choice as an electronic component in molecular devices, but it has proved very difficult until now to use them for the large-scale production of molecular devices capable of be robust at room temperature. As part of a joint effort, research teams from the University of Warwick, EMPA and Lancaster and Bern Universities achieved electrical and mechanical stability in graphene-based junctions, millions of times smaller than the diameter of a human hair. They published today their findings in an article titled "Robust molecular devices based on graphene" in the journal Nature Nanotechnology.

Simple mechanically stable structures, such as graphene-type molecules, are easily produced by chemical synthesis, but on this very small scale they are subject to a range of limits when they are placed in a junction to form a electronic device, such as variations of molecule-electrode interface. Researchers are overcoming these limitations by separating mechanical and electronic stability requirements at the molecular level.

They produced an electrically efficient structure by building a stack of graphene-like molecules to form an electron path through graphene-type P-type orbital molecules (they are electron-shaped clouds). Dumbbells in which an electron can be found, with some degree of probability). This would open new avenues for using fascinating molecular properties, such as quantum interference that occurs on such a small scale, provided that sufficiently robust mechanical structures are available. For this, the research team has also created links between each molecule and a silicon oxide substrate. This gave the structure significant mechanical stability by effectively anchoring the stack of graphene-like molecules to the substrate using a silanization reaction. This is illustrated in the simplified diagram accompanying this press release.

Dr. Hatef Sadeghi of the School of Engineering at the University of Warwick, who led the theoretical modeling of this work, said:

"This method allowed us to design and produce electron-mechanically and mechanically stable graphene-based molecular devices over a wide temperature range, which was achieved by uncoupling the mechanical anchoring of electronic pathways by combining a covalent bond of substrate molecules and large π conjugated headgroups.

"The junctions were reproducible on multiple devices and operated from 20 Kelvin at room temperature.Our approach represents a simple but powerful strategy for the future integration of molecule-based functions into stable and controllable nanoelectronic devices."