Self-Assembly of Organic Molecules on Atomically Flat Surfaces Opens New Perspectives Towards

Tailoring 2D organic crystals at the nanoscale

Denis Fichou

CEA-Saclay, Labo Nanostructures et Semi-Conducteurs Organiques CNRS-CEA-UPMC, SPCSI/DRECAM, Bât. 462, F-91191 Gif-sur-Yvette, France

Self-assembly of functional organic molecules on atomically flat surfaces opens new perspectives towards “molecular nanoelectronics”, a realistic strategy in the miniaturization of electronic devices. One simple way to investigate 2D supramolecular self-assemblies at the nanoscale is to generate them at a liquid-solid interface and observe them in situ by means of scanning tunneling microscopy (STM). A variety of 2D architectures have been recently obtained with functional molecules (liquid crystals, molecular wires, graphite-like molecules, etc) by controlling the subtle interplay between molecule-molecule and molecule-substrate interactions.

In this presentation, we first illustrate this approach with various families of conjugated compounds such as alkoxy-triphenylenes, star-shaped oligothiophenes, triazatrinaphthylenes, etc1-4. One step further, we demonstrate the possibility to work in the vertical dimension and pile-up two or three layers of similar or different molecules on top of each other.5 Even further, we use very long n-alkanes physisorbed on a solid substrate (graphite, gold) as tailored templates for the growth of complex self-assembled bi- and trilayers of large conjugated discal molecules possessing electrical and/or optical properties.6 Finally, we show that STM allows for the first time to image the surface of a bulk single crystal organic semiconductor (rubrene) down to molecular resolution and to record its local I/V curves in the dark and under photoexcitation.7

STM image (36x36 nm2) and schematic representation of a supramolecular “edge-on” columnar stack of large disclike molecules

References

1. A. Marchenko, N. Katsonis, D. Fichou, C. Aubert, M. Malacria, J. Am. Chem. Soc. 124, 9998 (2002).

2. N. Katsonis, A. Marchenko, D. Fichou, J. Am. Chem. Soc. 125, 13682 (2003).

3. N. Katsonis, A. Marchenko, D. Fichou, Adv. Mater. 16, 309 (2004).

4. N. Saettel, N. Katsonis, A. Marchenko, MP. Teulade-Fichou, and D. Fichou J. Mater. Chem. 15, 3175 (2005).

5. L. Piot, A. Marchenko, J. Wu, D. Fichou, and K. Müllen, submitted.

6. L. Piot, A. Marchenko, J. Wu, D. Fichou, and K. Müllen, J. Am. Chem. Soc. 127, 16245 (2005).

7. E. Menard, A. Marchenko, V. Podzorov, M.E. Gershenson, J.A. Rogers, D. Fichou, submitted.