A simple micromachining approach to testing nanoscale metal–self-assembled monolayer–metal junctions

We present a 'flip chip' technique for testing electronic self-assembled monolayers (SAMs). Metal–SAM–metal junctions with contact areas of approximately (25 nm)2 and smaller have been created and tested. While the approach is similar in spirit to conductive atomic force microscope measurements, it requires only straightforward optical lithography to create the test chips and a simple gravitational-force flexure to close the junction with sub-angstrom scale precision. The junction is formed in a vertical manner, in which the SAM is grown on one or both metal electrodes, and the circuit is closed via the pressure-induced flexing of one chip into another. This method of creating a junction is rapid and facilitates multiple measurements per chip set. We have investigated the electrical transport characteristics of a variety of SAMs using this technique, including aliphatic alkanethiols and aromatic dithiols. Results are consistent with junction contact areas , and elucidate information regarding the role of pressure and defects on SAM transport.