AVS 65th International Symposium & Exhibition
    Thin Films Division Thursday Sessions
       Session TF+PS-ThM

Paper TF+PS-ThM1
ALD and Diffusion in High Aspect Ratio Carbon Nanotube Forests

Thursday, October 25, 2018, 8:00 am, Room 104B

Session: Deposition Processes for 3D and Extreme Geometries
Presenter: David Kane, Brigham Young University
Authors: D. Kane, Brigham Young University
R.C. Davis, Brigham Young University
R.R. Vanfleet, Brigham Young University
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Very high aspect ratio or nanostructured materials have numerous applications. In many of those applications, the surface is decorated by atomic layer deposition or other vapor phase deposition techniques. In these extreme geometries the uniformity of deposition is a function of the interplay between transport (diffusion) and reaction rates. The A-B cycling in Atomic Layer Deposition (ALD) separates the deposition reaction from the transport. We have observed a limited penetration depth which decreases with cycle number in ALD on vertically aligned multiwall carbon nanotube (MWCNT) forests with an effective aspect ratio of 1000. Models of ALD in high aspect ratio features based on Knudsen diffusion transport combined with a simple geometric model of nucleation and growth on surfaces with a low nucleation site density can qualitatively reproduce the observed deposition. Fitting the models to the data allows extraction of the diffusion coefficients for these confined geometries.