Molecular three-terminal devices: fabrication and measurements

Incorporation of a third, gate electrode in the device geometry of molecular junctions is necessary to identify the transport mechanism. At present, the most popular technique to fabricate three-terminal molecular devices makes use of electromigration. Although it is a statistical process, we show that control over the gap resistance can be obtained. A detailed analysis of the current-voltage characteristics of gaps without molecules, however, shows that they reveal features that can mistakenly be attributed to molecular transport. This observation raises questions about which gaps with molecules can be disregarded and which not. We show that electrical characteristics can be controlled by the rational design of the molecular bridge and that vibrational modes probed by electrical transport are of potential interest as molecular fingerprints.