Flux-Dependent Growth Kinetics and Diameter Selectivity in Single-Wall Carbon Nanotube Arrays

The nucleation and growth kinetics of single-wall carbon nanotubes in aligned arrays have been measured using fast pulses of acetylene and in situ optical diagnostics in conjunction with low pressure chemical vapor deposition (CVD). Increasing the acetylene partial pressure is shown to decrease nucl...

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Bibliographic Details
Published inACS nano Vol. 5; no. 10; pp. 8311 - 8321
Main Authors Geohegan, David B, Puretzky, Alex A, Jackson, Jeremy J, Rouleau, Christopher M, Eres, Gyula, More, Karren L
Format Journal Article
LanguageEnglish
Published United States American Chemical Society 25.10.2011
Subjects
ACETYLENE
Arrays
CARBON
CATALYSTS
CHEMICAL VAPOR DEPOSITION
density
DISTRIBUTION
Flux
growth kinetics
in situ diagnostics
KINETICS
MATERIALS SCIENCE
Nanostructure
nanotube
NANOTUBES
NUCLEATION
PARTIAL PRESSURE
SCATTERING
Single wall carbon nanotubes
TRANSMISSION ELECTRON MICROSCOPY
growth rate
pulsed growth
in situ
nucleation
diagnostics
real-time
chemical vapor deposition
partial pressure
induction time
flux
aligned
kinetics
single wall carbon nanotubes
diameter distribution
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Summary:The nucleation and growth kinetics of single-wall carbon nanotubes in aligned arrays have been measured using fast pulses of acetylene and in situ optical diagnostics in conjunction with low pressure chemical vapor deposition (CVD). Increasing the acetylene partial pressure is shown to decrease nucleation times by three orders of magnitude, permitting aligned nanotube arrays to nucleate and grow to micrometers lengths within single gas pulses at high (up to 7 μm/s) peak growth rates and short ∼0.5 s times. Low-frequency Raman scattering (>10 cm–1) and transmission electron microscopy measurements show that increasing the feedstock flux in both continuous- and pulsed-CVD shifts the product distribution to large single-wall carbon nanotube diameters >2.5 nm. Sufficiently high acetylene partial pressures in pulsed-CVD appear to temporarily terminate the growth of the fastest-growing, small-diameter nanotubes by overcoating the more catalytically active, smaller catalyst nanoparticles within the ensemble with non-nanotube carbon in agreement with a growth model. The results indicate that subsets of catalyst nanoparticle ensembles nucleate, grow, and terminate growth within different flux ranges according to their catalytic activity.
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DE-AC05-00OR22725
USDOE Office of Science (SC)
ISSN:1936-0851
1936-086X
DOI:10.1021/nn2030397