Conformal SiNx Coating on Carbon Nanotubes via Transient UV-Ozone Functionalization and Two-Step Atomic Layer...

Area of Science:

• Materials Science
• Nanotechnology
• Surface Chemistry

Background:

• Carbon nanotubes (CNTs) possess unique properties but require surface modification for advanced applications.
• Achieving uniform coatings on complex nanostructures like CNTs presents significant challenges.
• Atomic Layer Deposition (ALD) is a powerful technique for thin film deposition, but its effectiveness on CNTs depends on surface preparation.

Purpose of the Study:

• To develop a method for achieving conformal silicon nitride (SiNx) coatings on carbon nanotubes (CNTs).
• To investigate the role of UV-ozone surface functionalization and a two-step ALD process in controlling SiNx deposition on CNTs.
• To optimize the process parameters for uniform SiNx coverage and minimal structural damage to the CNT network.

Main Methods:

• Transient UV-ozone treatment was used to functionalize the CNT surface, introducing oxygen-containing groups.
• A two-step ALD process involving low-temperature nucleation (100 °C) followed by high-temperature growth (700 °C) was employed for SiNx deposition.
• Characterization techniques, including Raman spectroscopy (monitoring I_D/I_G ratio), were used to assess CNT structural integrity and SiNx coverage.

Main Results:

• UV-ozone treatment increased CNT defect density, with optimal functionalization achieved at 7 minutes, preserving CNT structure.
• Direct high-temperature ALD resulted in incomplete SiNx coverage due to insufficient nucleation.
• The two-step ALD process significantly improved conformal SiNx deposition on CNTs, with subsequent annealing and ALD reducing defect levels.

Conclusions:

• A combination of transient UV-ozone functionalization and a two-step ALD process is effective for achieving conformal SiNx coatings on CNTs.
• The process parameters, particularly the duration of UV-ozone exposure and the staged ALD temperatures, are critical for successful deposition.
• This method offers a pathway for enhancing the properties and expanding the applications of CNT-based materials.