An efficient nanopatterning strategy for controllably fabricating ultra-small gaps as a highly sensitive...

Area of Science:

• Materials Science
• Nanotechnology
• Spectroscopy

Background:

• Fabricating large-scale, high-density nanogaps is critical for ultra-sensitive surface-enhanced Raman scattering (SERS) substrates.
• The ultrathin alumina mask (UTAM) technique produces nanoparticle (NP) arrays with 5 nm gaps but struggles with reliable large-area nanogap distribution due to pore wall collapse.

Purpose of the Study:

• To develop an efficient method for fabricating large-scale UTAMs with controlled nanogap sizes.
• To enhance the sensitivity and reproducibility of SERS substrates by creating ultra-small nanogaps.

Main Methods:

• A novel two-step poikilothermal pore-widening process was employed to precisely etch UTAM pore walls.
• This method prevented UTAM fragmentation, yielding large-scale UTAMs with approximately 5 nm pore wall thickness.
• The prepared UTAMs were used as templates for fabricating nanoparticle arrays.

Main Results:

• Large-scale nanoparticle arrays with high-density sub-5 nm and smaller gaps were successfully realized.
• SERS substrates fabricated with these sub-5 nm gaps exhibited ultrahigh sensitivity, with signal enhancement improving by an order of magnitude compared to 5 nm gaps.
• The method demonstrated good reproducibility for the fabricated nanoparticle arrays.

Conclusions:

• The developed two-step poikilothermal pore-widening technique effectively overcomes UTAM fragmentation issues.
• This technique enables the large-scale fabrication of ultra-small nanogaps, crucial for high-performance SERS substrates.
• The findings highlight the practical feasibility of this method for advancing SERS applications.