Paper EM+NC-WeA2
Silicon-on-Insulator based sub 10 nm Spaced Metal Electrodes for Hybrid Molecular Electronics

Wednesday, October 22, 2008, 2:00 pm, Room 210

In future microelectronic circuits a partial replacement of certain electronic functions by organic molecule junctions may become feasible. For such “hybrid” integration the fabrication of nanoscale contacts on the same semiconductor wafer using existing microelectronic process technology, only, will be advantageous. We investigated the fabrication of nanogap electrode devices based on silicon-on-insulator, by using optical lithography, a combination of dry and wet etching techniques and thin-film metal deposition. The prepared, smooth metallic contact pairs are separated by predetermined distances down to below 10 nm, and feature a well tailored material layer structure, as characterized by cross-sectional scanning TEM analysis. We studied the electronic transport properties of molecular wires based on conjugated organic molecules and molecule-nanoparticle hybrid systems. In the case of approx. 12 nm long dithiolated, oligo-phenylene-vinylene derivatives we observed a pronounced non-linear current-voltage characteristic at 4.2 K. The electronic states of the molecule have been studied by Density Functional Theory (DFT) in order to show the effect of the ligands and of the gold contacts. By using the results of the DFT calculations in a Non Equilibrium Green Function model, the current-voltage characteristics of OPVs have been analyzed, showing a good agreement with the experimental data. Low temperature transport through 30 nm gold nanoparticles positioned onto electrodes coated by a self-assembled monolayer of mercaptohexanol features a distinct Coulomb staircase behavior. These measurements are in excellent agreement with classical Coulomb blockade theory for an asymmetric double barrier tunneling system.