Deterministic thermal micro-reflow of lithographic structures for Sub-10-nm metallic gaps fabrication

Abstract

Metallic nanogaps are a kind of fundamental building blocks for nanoelectronics and nanoplasmonics. However, its reliable fabrication remains challenging and thus developing additional approaches to fabricate ultrasmall metallic nanogaps is still required. In this work, we report a directed self-assembly approach to fabricate metallic nanogaps based on glass-transition-induced micro-reflow of polymer/metal hybrid structures. The process involves three main steps: electron-beam lithography process to obtain initial polymer structures, metal deposition onto the pre-patterned polymer nanostructures, and the solvent-assisted reflow process. It is interesting that the flowing orientation of polymer/metal hybrid nanostructures undergoing glass transition can be determined via several asymmetrical geometrical parameters including shapes and initial nanogaps. Mechanical simulations based on thermo-mechanical coupled finite element method are used to qualitatively understand the mechanism of the deterministic thermal reflow phenomenon. We demonstrate that this method is effective to fabricate sub-10-nm metallic nanogaps in gold nanostructures, which may have potential applications in plasmon-enhanced light-matter interactions, ultrafast nanotransistors, nanoelectronics and molecular electronics.