Fabrication of sub-5nm gap using on-wire lithography

Abstract

One dimensional multisegmented gapped nanowires have sparked research interest because they can be used for various applications like in biological detection and encoding systems. Gapped nanowire structures can also facilitate the study of electronics properties of nanomaterials. In this final year project, the objective is to synthesize Au-Ni-Au configuration nanowires with 5nm gap size using On-Wire Lithography (OWL). The gap size is determined by the Ni segment length which can be removed by wet chemical etching.

On-Wire Lithography (OWL) allows us to control the gap size down to the 5nm length scale. This technique has higher reliability & throughput but lower cost compared with other known lithographic techniques. Thus this project investigates what are the optimum synthesis parameters that allow us to obtain such sub-5m gaps. Effects on length and morphology of Ni segments by varying the deposition potential have been investigated. The relationship between the amount of charge deposited and the corresponding length have also been found. Pulsed electrochemical deposition has been identified as a way to improve the original rough interface between individuals segments. With smoother interfaces, the scope of utility will be increased for OWL generated structures.

In a nutshell, 8nm Ni segment lengths have been successfully obtained using OWL. Although this result falls short of our aim of fabricating 5nm gap size, with appropriate electrochemical control coupled with the recommendation made in the conclusion part of the report, this number can definitely be reduced further.