24 August 2010 Atomic layer deposition for aligned growth of and conformal deposition onto double and triple walled carbon nanotubes
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We present our work on the growth and functionalization of carbon nanotubes (CNTs). A significant challenge in the growth of aligned single, double and triple walled nanotubes is in the deposition of a controlled thickness catalyst layer. Conventional techniques using line of sight deposition such as sputtering and evaporation produce uniform catalyst layers only when extreme care is taken in the placement of flat substrates. Growth of aligned low wall number carbon nanotubes on contoured, complex geometry, or large surface area substrates is simply not technically feasible through these techniques. Using iron atomic layer deposition (ALD) with ferrocene and oxygen precursors for catalyst deposition circumvents the line of sight problems and allows for uniform coverage across almost all substrates. Furthermore the ALD technique allows for extremely accurate and reproducible thickness depositions. Using these ALD catalyst layers reproducible aligned arrays consisting of primarily double and triple wall CNTS can be fabricated. Conformal coatings onto high aspect ratio surfaces are particularly challenging. The walls of single carbon nanotubes in a nanotube array are inaccessible by line of sight techniques. ALD circumvents this problem by relying on a gas-surface reaction to initiate growth. Generally, growth of ALD films on CNTs results in beading of the deposited materials around CNT defects. This is particularly true of high surface energy materials. The number of nucleation sites and the onset of growth of Pt by ALD can be tuned by use of Ar plasma, O2 plasma and chemical functionalization.
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A. Dameron, A. Dameron, J. Bult, J. Bult, S. Pylypenko, S. Pylypenko, C. Engtrakul, C. Engtrakul, C. Bochert, C. Bochert, L. Chen, L. Chen, J. Leong, J. Leong, S. Frisco, S. Frisco, L. Simpson, L. Simpson, H. Dinh, H. Dinh, B. Pivovar, B. Pivovar, } "Atomic layer deposition for aligned growth of and conformal deposition onto double and triple walled carbon nanotubes", Proc. SPIE 7761, Carbon Nanotubes, Graphene, and Associated Devices III, 776108 (24 August 2010); doi: 10.1117/12.861090; https://doi.org/10.1117/12.861090

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