Nanogap electrodes formed at the exposed edge of Au/self-assembled monolayer/Al2O3/Au tunnel structures grown by atomic layer deposition

Atomic layer deposition of high quality Al2O3 thin films onto Au electrodes was enabled by surface modification with a self-assembled monolayer of –OH groups that react with a monolayer of trimethylaluminum gas source. Ar ion milling was then used to expose the edge of the Au/insulator/Au structure for molecular electrode contacts. The junctions are characterized by atomic force microscope and tunnel current properties. The Au/self-assembled monolayer/Al2O3/Au tunnel junction, with a very thin oxide insulator layer (15.4 Å), is stable and has a small tunneling current density of about 0.20–0.75 A/cm2 at 0.5 V.