A method offering precise control over the synthesis conditions to obtain carbon
nanotube (CNT) samples of a single chirality (metallic or semi-conducting) is presented.
Using this nanolithographic method of catalyst deposition, the location of CNT growth is
also precisely defined.
This technique obviates three significant hurdles that are preventing the exploitation
of CNT in micro- and nano-devices. Microelectronic applications (e.g., interconnects,
CNT gates, etc.) require precisely defined locations and spatial density, as well as
precisely defined chirality for the synthesized CNT. Conventional CVD synthesis
techniques typically yield a mixture of CNT (semi-conducting and metallic types) that
grow at random locations on a substrate in high number density, which leads to extreme
difficulty in application integration.
Dip Pen Nanolithography (DPN) techniques were used to deposit the catalysts at
precisely defined locations on a substrate and to precisely control the catalyst
composition as well as the size of the patterned catalyst. After deposition of catalysts, a
low temperature Chemical Vapor Deposition (CVD) process at atmospheric pressure
was used to synthesize CNT. Various types of catalysts (Ni, Co, Fe, Pd, Pt, and Rh) were
deposited in the form of metal salt solutions or nano-particle solutions. Various characterization studies before and after CVD synthesis of CNT at the location of the
deposited catalysts showed that the CNT were of a single chirality (metallic or semiconducting)
as well as a single diameter (with a very narrow range of variability).
Additionally, X-ray photoelectron spectroscopy (XPS) was used to characterize the
deposited samples before and after the CVD, as was lateral force microscopy (LFM) for
determination of the successful deposition of the catalyst material immediately after
DPN as well as following the CVD synthesis of the samples. The diameter of the CNT
determines the chirality. The diameter of the CNT measured by TEM was found to be
consistent with the chirality measurements obtained from Raman Spectroscopy for the
different samples. Hence, the results showed that CNT samples of a single chirality can
be obtained by this technique. The results show that the chirality of the synthesized CNT
can be controlled by changing the synthesis conditions (e.g., size of the catalyst patterns,
composition of the catalysts, temperature of CVD, gas flow rates, etc.).
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/ETD-TAMU-2539 |
| Date | 15 May 2009 |
| Creators | Huitink, David Ryan |
| Contributors | Banerjee, Debjyoti |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Thesis, text |
| Format | electronic, application/pdf, born digital |
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