Web Release Date: October 17,
Flying and Crawling Modes during Surface-Bound Single Wall Carbon Nanotube Growth
and
Department of Engineering, University of Cambridge, CB3 0FA Cambridge, United Kingdom, Micro and Nanosystems, ETH Zurich, 8092 Zurich, Switzerland, Hitachi Cambridge Laboratory, CB3 0HE Cambridge, United Kingdom, LeRoy Eyring Center for Solid State Science, Arizona State University, 85287-1704 Tempe, Arizona, and Department of Materials Science and Metallurgy, University of Cambridge, CB2 3QZ Cambridge, United Kingdom
Received: July 5, 2007
In Final Form: August 27, 2007
Abstract:
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.
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