Transport in self-assembled molecular wires: Effect of packing and order

We show that orientation, packing, and order play a vital role in determining the current-voltage (I-V) characteristics of self-assembled molecular wires, an important issue which can affect the performance of molecular electronic devices. By topographic and tunneling spectroscopic studies on monolayers of a molecule assembled with and without molecular order, we show that competing forces due to the electric field, intermolecular interactions, tip-molecule physisorption, and substrate-molecule chemisorption influence the transport measurements and its reproducibility. We also find that asymmetry in the I-V is caused both by the molecular structure and the contact geometry.