Metallic nanogaps with access windows for liquid based systems

A new method has been established for the reproducible fabrication of high quality, metallic nanogaps on silicon chips suitable for liquid based nanometer scale devices. Realization of μm structures connected to nanogaps with gap sizes down to 30 nm has been achieved by a combination of an optical and an electron-beam (e-beam) lithography step using an optimised adhesion layer/metallic layer combination (Ti/Pt/Au—three layer combination) and an adopted two layer e-beam resist. The quality of the interconnects between optically and e-beam lithographically defined structures and the surface roughness of the gold nanogaps have been improved by a controlled temperature treatment. With this method the production of a variety of different gap shapes could be demonstrated. Specifically the lithographic structures have been successfully covered by a protection layer, except of a 200 nm×400 nm size access window located on top of the nanogaps, making it suitable for applications in liquid environment such as molecular and/or electrochemical metal deposition.