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Bottom-Up Growth of Carbon Nanotube Multilayers: Unprecedented Growth
 

Summary: Bottom-Up Growth of Carbon Nanotube
Multilayers: Unprecedented Growth
Xuesong Li, Anyuan Cao, Yung Joon Jung, Robert Vajtai, and
Pulickel M. Ajayan*,
Department of Materials Science & Engineering, Rensselaer Polytechnic Institute,
Troy, New York 12180, and Department of Mechanical Engineering, UniVersity of
Hawaii at Manoa, Honolulu, Hawaii 96822
Received July 29, 2005
ABSTRACT
An unusual growth phenomenon, with no precedent in vapor-phase thin film growth, is described here, for the case of the growth of stacked
multiple layers of vertically aligned carbon nanotubes1-6 on solid substrates. As multiple layers of ordered nanotubes are sequentially deposited
from the vapor onto the substrate, each layer nucleates and grows from the original substrate surface at the bottom of the existing multiple
stacks of nanotubes. In contrast to conventional understanding of thin film deposition,7 the mechanism here has similarities to porous oxide
film formation on surfaces.8 The stacked layers of aligned nanotubes act as fully permeable membranes for the downward diffusion of growth
precursor vapors, allowing growth to occur at the buried solid interface. The preexisting multiple nanotube stacks lift up to accommodate the
vertical growth of fresh layers, allowing the formation of nanotube towers extending in millimeter lengths. Our results provide evidence for
a new growth phenomenon, characterized by selective, interface-driven, bottom-up growth of self-assembled nanowires at buried interfaces,
covered with weakly adhering thick porous membranes.
There have been many previous reports on the growth1-5
and applications9-12 of vertically aligned multiwalled carbon

  

Source: Ajayan, Pulickel M. - Department of Mechanical Engineering and Materials Science, Rice University

 

Collections: Materials Science