Graphene as a substrate for assembling small organic molecules and heterostructures

Researchers at the University of Stanford in the US, the Ulsan National Institute of Science and Technology (UNIST) in South Korea and Queen’s University in the UK showed that graphene is an excellent substrate for assembling small organic molecules and that such heterostructures might be used in applications like high-performance detectors, solar cells and flexible transistors.

The researchers began by preparing suspended graphene films. They then evaporated C60 molecules onto the films to form thin-film crystals.They then made the resulting structures up into vertical transistors doped with n-type semiconducting materials and found that these devices have current on/off ratios of more than 3 x 103. Various transmission electron microscopy techniques, including selective area electron diffraction, atomic resolution TEM imaging, and van der Waals-based first principles computational methods allowed the researchers to study the structure and grain size of the crystals in detail and carefully look at the graphene-C60 interface in particular. They also noticed that the C60 films lay uniformly on the graphene substrate and that the individual molecules can assume several different molecular orientations.

Since both graphene and organic C60 thin films are good materials for flexible electronics devices, the heterostructures could readily be incorporated into flexible transistors and other such components. The team says it will be looking at ways to grow various other organic semiconductor thin films (including polymer thin films) onto graphene. According to the scientists, their approach allows them to the tune the electrical properties of the vertical heterostructures they make, which will help to develop better performing devices.

Posted: Jun 17,2015 by Roni Peleg