Paper TF-WeM5
Nucleation and Ultra-Thin Film Formation during ALD on Multiwall Carbon Nanotubes

Wednesday, October 20, 2010, 9:20 am, Room Ruidoso

Atomic layer deposition is widely studied as a means to coat and encapsulate polymers to impede diffusion of water, oxygen or other species. ALD is also a viable means to coat and surface functionalize carbon nanotubes and other nanostructured materials. Previous work suggests that ALD nucleation proceeds differently on single and multiwalled carbon nanotubes, where the more defective nature of multiwalled tubes allows more rapid nucleation and film growth. In this work, we are interested in using ALD to encapsulate multiwall carbon nanotubes with as thin a layer as possible, to modify the chemical signature of the nanotubes while maintaining their advantageous mechanical and physical properties. Our motivation for this work is to explore means to alter potential toxic inhalation effects that carbon nanotubes may present, for example, in manufacturing facilities producing nanotube-based products. We have worked with multiwall nanotubes from Helix Materials Solutions as well as from Mitsui. The Mitsui tubes are 30-50 nm in diameter and contain many concentric nanotubes. TEM analysis shows that ALD using TMA/water at 90 C proceeds slowly at first, producing isolated nuclei for the first 15 cycles. Films are smoother after 25 cycles, and continuous film coatings are observed after 80 cycles, corresponding to film thickness of 3.8 nm. After complete film coverage, the film growth rate increases to values close to that expected for TMA/water at this process temperature. We will present results regarding how these coatings affect physical properties of the nanotubes, including surface wetting, as well as possible new means to coat large numbers of nanotubes in a conventional viscous flow reactor system.