CVD growth procedure [19]. Spawned by a report that an amorphous carbon
coating on the catalyst particles was "poisoning" them and terminating the growth
[20], their supergrowth procedure helped to produce a reducing environment inside
the reaction chamber which cut down on amorphous carbon and lead to the growth
of A-SWNT forests up to 2.5 mm long. Later, Amama et al. suggested that the
success ofwater in the supergrowth procedure was owed to the decoration of the
inter-catalyst substrate space with hydroxide species, thereby stifling the Ostwald
ripening of the catalyst particles in the high temperature growth environment [21].
Further refining of this water-assisted technique in the recent past has lead to the
growth of forests up to 5 mm tall, and the discovery that the continuous flow of
water vapor during the cool-down of the furnace after growth will serve as a weak
oxidizer which will cause the CNTs to detach from the substrate, leaving a free-
standing film of CNTs [22].
CVD is a method which has been considerably improved in the decade-and-a-
half since its inception as a CNT synthesis method, and is the favored method for
producing very large quantities due not only to the scalability of the procedure, but
also its low cost. Unfortunately, while advances have been made, it is still not nearly
as effective in producing top-quality CNTs as the other common methods.
In Chapter 2,1 will describe the CVD procedures for growing A-CNT arrays
with more depth, and will specifically describe the methods used to produce the
aligned CNTs for this work.