Flying and Crawling Modes during Surface-Bound Single Wall Carbon Nanotube Growth

Growth modes of single wall carbon nanotubes are investigated during chemical vapor deposition within an
environmental transmission electron microscope and in furnace reactors at different gas pressure and flow
conditions. The nanotube pivoting observed by in situ microscopy can be explained by dynamic catalyst
crystallite reshaping for base growth. Microfabricated substrate barriers and gaps allow for the distinction
between “crawling” and “flying” nanotubes, referring to either a continuous intimate contact with the substrate
dominated by van der Waals forces or a mere substrate anchoring of nanotubes held afloat during growth.
Flying nanotubes grow unobstructed and straight to millimeter lengths and are susceptible to external forces.
Crawling nanotubes are strongly affected by substrate topography. We relate this to tip and base growth
regimes and discuss how the growth modes can be controlled.