Fabrication of sub-5 nm gaps between metallic electrodes using conventional lithographic techniques

The reproducible fabrication of nanoscale gaps below 5nm between metallic electrodes is key to the study of the electronic characteristics of individual molecules, but is hampered by the resolution limit and mechanical instabilities of commonly used electron-sensitive resists. We describe a fabrication process for the creation of nanoscale gaps between metallic electrodes based on conventional lithographic techniques. The process involves the patterning of a lithographic gap of 5–∼20nm between metallic electrodes on an oxidized silicon substrate. The SiO2 not covered by the electrodes is undercut and another metal film is thermally evaporated onto the substrate. Due to the slow buildup of material at the edges of the patterned electrode, the gap size can be reduced in a controllable way, and the final gap size is determined by the thickness of the evaporated metal film. This batch fabrication process is suitable for high-density fabrication of nanoscale gaps with the attractive feature that a self-aligned...