Towards molecular electronics with scalable nanopore junctions*

We have fabricated and measured nanoscale molecular junctions. Each device consists of a shallow pore in an oxide layer, with a self-assembled monolayer (SAM) on a gold surface at the bottom. The use of a conductive polymer as a top-contact avoids previously noted issues of metal diffusion into contacted SAMs. Larger pores are more likely to contain monolayer defects and dislocations, thus nanometer-scale control over the pore size allows us to investigate transport through the SAM as a function of defect density. The planar geometry and use of robust materials in the device allows for additional molecular synthesis after monolayer formation. For example, we use ``click'' chemistry to alter the functionality of SAMs of azide-terminated alkanethiols. The use of mixed monolayers to substantially dilute the number of conducting molecules in a 50-nanometer diameter pore allows us to observe few to single-molecule transport behavior.