Sensitive SERS detection at the single-particle level based on nanometer-separated mushroom-shaped plasmonic dimers

Area of Science:

• Nanotechnology
• Materials Science
• Spectroscopy

Background:

• Elevated metallic nanostructures with sub-10 nm nanogaps offer enhanced surface-enhanced Raman scattering (SERS) through synergistic effects.
• Efficient substrate decoupling in three-dimensional (3D) designs is crucial for maximizing SERS performance.

Purpose of the Study:

• To demonstrate a pattern-transfer-free process for creating elevated, nanometer-separated mushroom-shaped dimers.
• To achieve precise control over sub-10 nm nanogap sizes for optimized plasmonic applications.

Main Methods:

• Utilizing a gap-narrowing effect during metallic film deposition on 3D resist patterns.
• Controlling initial nanogap size in resist structures and deposited film thickness for tunable nanogaps.
• Employing experimental and simulation methods to analyze SERS enhancement.

Main Results:

• Successfully fabricated elevated mushroom-shaped dimers with sub-10 nm nanogaps with single-digit nanometer precision.
• Demonstrated higher SERS enhancement factors for gold dimers on mushroom-shaped pillars compared to other configurations.
• Validated the capability of nanogap-tuned elevated dimers for significant field enhancement.

Conclusions:

• The developed pattern-transfer-free method reliably produces elevated nanogaps for SERS.
• Elevated nanogapped dimers, particularly mushroom-shaped ones, represent an ideal platform for maximizing plasmonic field enhancement.
• This approach holds promise for advancing various plasmonic applications requiring high sensitivity.