Fundamental interface properties in OFETs: Bonding, structure and function of molecular adsorbate layers on solid surfaces

The functionality of organic field effect transistors resides in their interfaces. Highly ordered molecular adsorbate layers provide an excellent tool to study the relevant physical properties of these interfaces. In this article we focus on molecules at the organic/metal interface. We find that their geometry and electronic structure are very responsive to influences from the substrate and the molecular environment, while interface structures evolve cooperatively in the sway of interfacial and intermolecular interactions and can thus be extremely complex. Although our results cannot be transferred directly to real devices, a number of intriguing physical effects emerge that could play an important role in (nanoscale) OFETs, e.g. an anomalously strong energy band dispersion at the organic/metal interface, a remarkable plasticity of the electronic structure of molecules in ultra-thin films, and Kondo physics in a non-magnetic molecular wire. Finally, we report the realization of a mechanically gated single-molecule transistor that allows investigating the transport physics in a molecular wire as a function of contact properties. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)