Absence of strong gate effects in electrical measurements on phenylene-based conjugated molecules

The electronic transport characteristics of self-assembled monolayers of phenylene-based π-conjugated molecules were measured in a three-terminal device geometry. The short (∼1 nm) molecules were connected between two gold electrodes with a nearby Al₂O₃/Al gate electrode. It was possible to fabricate working devices using three of the five molecules investigated. The other two types of molecules led to devices where the Au electrodes were shorted together. Current-voltage characteristics as a function of the gate voltage are presented for the other three molecules. For some devices with 1,3-benzenedithiol, a weak gate effect was observed but no gating effect was observed for devices fabricated with the other molecules. The results are in strong contrast with those reported by Schön et al.