Dr Joe Smerdon

Large accumulations of molecules perform quite well within simple electronics, exemplified by display OLEDs and solar cells. However, they are no use for digital electronics unless the size of components can be reduced to something at least as small as a silicon diode. One might think that molecules have the edge here; a silicon diode is at least 50 nm on a side in the latest technology, whilst small functional molecules can be around 1 nm in largest dimension. The difficulty is in controlling matter on this scale and also in reproducing macroscale behaviour: experimental systems of one or two molecules generally fail to come close to the predictions of computational modelling. Joe's work in this area led to two highly-cited papers in 2011, establishing the groundwork for the molecules in question and verifying the technical approach. A paper in the prestigious ACS Nano journal followed in 2013 with the first hints of molecular diode action. Despite having left Argonne in 2012, Joe returned yearly since to continue working on this project. The latest papers, in Nano Letters and The Journal of Chemical Physics, describe a pair of the best performing molecular diodes yet reported, with performance orders of magnitude above the next best attempts, and a simplicity of fabrication and operation that has opened up new ways to investigate molecular electronics. On the strength of the initial Nano Letters work the collaboration were invited to contribute the aforementioned article to a special issue of The Journal of Chemical Physics on molecular electronics. The contribution was chosen as the cover feature of the issue. Joe's other major contribution so far is the discovery of a method to produce 2-dimensional molecular quasicrystals. He used the same molecules as in the studies mentioned above, as they are archetypes for the study of molecular adsorption geometries (in addition to being archetypal molecular semiconductors), as a fullerene is a ball (0-dimensional) and a pentacene is a rigid rod (1-dimensional). He found that under certain conditions, they can be coaxed to form highly-ordered quasicrystalline films. The expansion of the field of quasicrystals into self-assembled molecular systems opens up heretofore unprecedented opportunities, including manipulating the passage of waves (such as photons or electrons) through material and hinting at the possibility of bending light around objects, or even the creation of monopolar magnetic systems, a kind of holy grail for physics researchers. However, the work he is doing now is the most important, both in terms of ambition and potential impact. He has assembled an international team of collaborators to run a project aimed at modifying the atomic structure of graphene in order to tailor its properties. The importance of this is twofold: first, we will acquire graphene with new properties (such as coloured light emission, efficient light harvesting or catalytic super-action); secondly, we will demonstrate that per-atom manufacturing is possible, finally realising the promise made by Richard Feynman in the 1950s.