In 1995, Smalley and co-workers reported the laser ablation technique [16],
which benefits from a much larger and predominantly SWNT yield. After vaporizing
a graphitic carbon / transition metal target with a laser in the presence of an inert
gas, the carbon will condense on cool surfaces in the reaction chamber, where CNTs
will begin to form. Despite its efficiency in producing large quantities of quality
CNTs, this technique is largely overlooked due to its prohibitive cost.
The majority of the CNT synthesis work over the rest of the 1990's and
2000’s was focused on understanding and refining the above methods to both
improve the quality and/or reduce the size distribution of these methods while
scaling up the production. These efforts have helped to expand CNT production into
the private sector, where the quality has improved significantly and the cost-per-
gram of CNTs has steadily dropped.
1.2.2. Chemical Vapor Deposition to Produce Aligned CNTs
One of the particularly interesting aspects of CVD is the ability to use this
method to synthesize self-aligned "forests" of carbon nanotubes (A-CNTs), as first
reported in 1996 by Li et al. [17]. The CNTs produced were exclusively MWNTs and
measured approximately 40 um in-length. Another evolution of the CVD technique
to grow A-CNTs, perhaps fueled by the success of the arc-discharge method, was the
introduction of a plasma source, as first reported in 1997 [18]. Their procedure
allowed for a lower growth temperature and the use of a much less specialized
substrate. In the mid 2000's, Hata and co-workers developed a technique they
termed "supergrowth" which involved the introduction of water vapor during the