A research team led by professor Daniel Vanmaekelbergh (Chemistry) has discovered how a new material with attractive electronic properties is formed. The properties can be controlled during the formation process. The new material combines the variable properties of semiconductor nanocrystals with the special effects that take place in materials with a honeycomb structure, such as graphene. Possible applications are ultrarapid electronics and use in a quantum computer. The results of the research were published on 29 May 2014 in Science.
In the publication the researchers describe their extensive experimental study of the new material. “Due to an exceptionally broad combination of analysis techniques, we now know the structure at both the atomic and nanometre scales”, explains FOM PhD researcher Mark Boneschanscher. Based on this, the researchers could subsequently derive the mechanism by which the nanocrystals form the honeycomb structure. “As a result of this we can control the formation of the new material so that it receives the exact properties desired.” The study published in Science was a collaboration between researchers from Utrecht University, Delft University of Technology, and physicists from Grenoble and Antwerp.
Nanocrystals can be viewed as artificial atoms. Researchers can change the size, composition and shape of the nanocrystals. A logical next step in the search for new materials is linking these artificial atoms together to form a superstructure. The research team did this by linking the nanocrystals together to form a honeycomb structure.
The honeycomb structure was chosen with good reason. Graphene, a single layer of carbon atoms in a honeycomb structure, has attracted considerable interest in recent years because of its huge potential for new ultrarapid electronics. That is because its honeycomb structure ensures that electrons can shoot through the material at a speed of more than one million kilometres per hour. However, a disadvantage of graphene is that it is not a semiconductor but is instead more similar to a metal. It is therefore not ideal for switching in electronic circuits or for optoelectronic applications, such as in screens and LEDs.
Best of both worlds
“The semiconductor nanocrystals in a honeycomb structure therefore combine the best of both worlds”, concludes Boneschanscher. He defended his doctoral thesis, which includes this research, on 4 June.
Long-Range Orientation and Atomic Attachment of Nanocrystals in 2D Honeycomb Superlattices, M.P. Boneschanscher, W.H. Evers, J.J. Geuchies, T. Altantzis, B. Goris, F.T. Rabouw, S.A.P. van Rossum, H.S.J. van der Zant, L.D.A. Siebbeles, G. Van Tendeloo, I. Swart, J. Hilhorst, A.V. Petukhov, S. Bals, and D. Vanmaekelbergh, Science, 29 May 2014
Below are the links to two films, which show reconstructions of the honeycomb structures. The films were made with the help of electron tomography. Between the moving images of the reconstruction models (colour) you can see the actual electron tomography images (black and white).
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