Influence of a Top Crust of Entangled Nanotubes on the Structure of Vertically Aligned Forests of Single-Walled Carbon Nanotubes

The time evolution of the growth process of vertically aligned single-walled carbon nanotubes (or V-SWNTs) on a flat substrate was examined by scanning electron microscopy (SEM), resonant Raman spectroscopy, and angle-resolved X-ray absorption near-edge structure (XANES). This detailed characterization gives evidence for the growth of a thin layer (crust) of randomly oriented single-walled carbon nanotubes during the first stages of the growth process. This crust is responsible for the unique forest-like morphology exhibited by this type of SWNT structure.