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Investigation of novel self-assembled Nano-Electronics - Towards tunable quantum-mechanical resonance

Final Activity Report Summary - INSANE (Investigation of novel self-assembled nano-electronics - towards tunable quantum-mechanical resonance)

Technological progress permits the controlled fabrication, characterisation, and visualisation of objects at the nanometer length scale. While the properties of macroscopic objects are usually determined by the bulk properties of the respective material, the properties of nanoscopic objects are often dominated by their surfaces - at these small length scales, there is no 'bulk', only surface. Naturally, such tiny objects need to somehow interact with the macroscopic world in order to perform a certain function. Consequently, not only surfaces but also the interfaces with macroscopic contacts play an important role. As, additionally, quantum-mechanical aspects of matter become increasingly dominant at the nanoscale, new theoretical models need to be found in order to establish a microscopic understanding and atomistic insight into surface- and interface effects.

The scientific goal of the Marie-Curie Outgoing International Fellowship 'Investigation of Novel Self-Assembled Nano-Electronics' (INSANE) was to investigate the properties of such interfaces by the means of computer-based quantum-mechanical simulations. More specifically, the objects under investigation were small organic molecules that spontaneously self-assemble into well-ordered monolayers on suitable substrates. Organic molecules are naturally 'nano'-sized functional building blocks, whose properties can be tuned through the full wealth of synthetic chemistry. Contacting either a single molecule or a thin film thereof with metallic electrodes permits the realisation of electronic and optoelectronic devices such as transistors and logical circuits, light-emitting devices or molecule-based organic solar cells.

By employing state-of-the-art computational techniques, the INSANE project unveiled novel phenomena at the metal / organic interface that will contribute importantly to the future development and improvement of such devices. In particular, relationships could be established between the chemical structure of the molecules, their orientation with respect to the metal surface, and their geometric structure on the surface on one hand and, on the other hand, how easily electrons, the fundamental carriers of electric charge responsible for electric current, can pass from the metal into the molecules. This is of major importance insofar as this step, the injection of electrons from the metal into the organic, is often a limiting factor for the performance of organic and molecular electronic devices. More importantly, a thorough understanding of these processes allowed establishing clear-cut guidelines for the future design of molecules, where there is no longer any residual barrier for electrons to pass from metal to molecule - the molecules essentially become part of the metal.

To summarise, the INSANE project employed computer-based quantum-mechanical modelling to gain fundamental insight into interfacial phenomena in an important class of nanoscopic systems - hybrid organic / inorganic devices. This insight could be translated into accessible guidelines for the future design of molecules and devices, paving the way for the truly knowledge-based development of novel technologies.