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.