Generating Multiscale Gold Nanostructures on Glass without Sidewall Deposits Using Minimal Dry Etching Steps

Area of Science:

• Nanoscience and Nanotechnology
• Materials Science
• Surface Engineering

Background:

• Fabricating micro- to nanometer-scale features is crucial for advanced technologies, especially in biological applications requiring transparent substrates.
• Traditional wet etching methods are insufficient for nanometer-scale features, while dry etching often requires harsh conditions and results in residual materials.
• Existing dry etching methods for gold struggle to achieve fine features without defects like sidewall deposits (veils).

Purpose of the Study:

• To develop an improved dry etching method for fabricating gold nanofeatures on transparent substrates.
• To achieve precise control over feature size and aspect ratio without compromising surface quality.
• To demonstrate the functionality of etched gold nanostructures for biological applications.

Main Methods:

• Utilized reactive ion etching (RIE) with a trifluoromethane (CHF3)/oxygen (O2) gas mixture at room temperature and mild pressure.
• Controlled the oxygen concentration during RIE to prevent sidewall deposits (veils) and achieve desired aspect ratios.
• Fabricated gold nanofeatures down to 50 nm on glass substrates.

Main Results:

• Successfully etched gold films to produce features as small as 50 nm with an aspect ratio of 2 in a single step.
• Achieved veil-free sidewalls and flat surfaces, suitable for subsequent material deposition.
• Demonstrated high electrical conductivity of the etched gold nanofeatures after carbon nanotube deposition, confirming their functionality as nanoelectrodes.

Conclusions:

• Developed a mild, single-step RIE process for creating high-quality gold nanofeatures on glass.
• The method offers a viable route for producing biocompatible, conductive, and stable gold nanostructures for biomedical and biological applications.
• The process overcomes limitations of traditional etching techniques, enabling advanced nanoscale fabrication for optical monitoring and device integration.