Investigating the Growth Process of Vertically Aligned Single-Walled Carbon Nanotubes Synthesized from Alcohol

We have performed a systematic investigation of the influence of growth parameters on the synthesis of vertically aligned single-walled carbon nanotubes (VA-SWNTs) by the alcohol catalytic chemical vapor deposition (ACCVD) method. The growth process of the VA-SWNTs was monitored using an in situ optical absorbance technique and the effects of CVD temperature and ethanol pressure on the initial growth rate and the catalyst lifetime were investigated. We found that for a given CVD temperature, there is an optimum pressure at which VA-SWNT film growth is maximized, and this pressure increases with temperature. Below this optimum pressure, the growth reaction is first-order, with the arrival of ethanol to the catalyst being the rate-limiting step. The activation energy of the growth reaction was determined to be approximately 1.5 eV. The root-growth mechanism of VA-SWNTs synthesized by the alcohol CVD method was also confirmed by a two-stage growth process. Following a short growth period using normal ethanol, C -labeled ethanol was introduced to continue the growth. The location of the C was determined from resonance Raman spectra, confirming the root-growth mechanism.