Diffusion- and Reaction-Limited Growth of Carbon Nanotube Forests

We present a systematic study of the temperature and pressure dependence of the growth rate of vertically aligned small diameter (single- and few-walled) carbon nanotube forests grown by thermal chemical vapor deposition over the temperature range 560−800 °C and 10−5 to 14 mbar partial pressure range, using acetylene as the feedstock and Al2O3-supported Fe nanoparticles as the catalyst. We observe a pressure dependence of P0.6 and activation energies of <1 eV. We interpret this as a growth rate limited by carbon diffusion in the catalyst, preceded by a pre-equilibrium of acetylene dissociation on the catalyst surface. The carbon nanotube forest growth was recorded by high-resolution real-time optical imaging

Diffusion- and Reaction-Limited Growth of Carbon Nanotube Forests

We present a systematic study of the temperature and pressure dependence of the growth rate of vertically aligned small diameter (single- and few-walled) carbon nanotube forests grown by thermal chemical vapor deposition over the temperature range 560−800 °C and 10−5 to 14 mbar partial pressure range, using acetylene as the feedstock and Al2O3-supported Fe nanoparticles as the catalyst. We observe a pressure dependence of P0.6 and activation energies of <1 eV. We interpret this as a growth rate limited by carbon diffusion in the catalyst, preceded by a pre-equilibrium of acetylene dissociation on the catalyst surface. The carbon nanotube forest growth was recorded by high-resolution real-time optical imaging

Growth of Ultrahigh Density Single-Walled Carbon Nanotube Forests by Improved Catalyst Design

We have grown vertically aligned single-walled carbon nanotube forests with an area density of 1.5 × 10¹³ cm^–2, the highest yet achieved, by reducing the average diameter of the nanotubes. We use a nanolaminate Fe–Al₂O₃ catalyst design consisting of three layers of Al₂O₃, Fe, and Al₂O₃, in which the lower Al₂O₃ layer is densified by an oxygen plasma treatment to increase its diffusion barrier properties, to allow a thinner catalyst layer to be used. This high nanotube density is desirable for using carbon nanotubes as interconnects in integrated circuits

Investigating the Diameter-Dependent Stability of Single-Walled Carbon Nanotubes

We investigate the long-standing question of whether electrons accelerated at 80 kV are below the knock-on damage threshold for single-walled carbon nanotubes (SWNTs). Aberration-corrected high-resolution transmission electron microscopy is used to directly image the atomic structure of the SWNTs and provides in situ monitoring of the structural modification induced by electron beam irradiation at 80 kV. We find that SWNTs with small diameters of 1 nm are damaged by the electron beam, and defects are produced in the side walls that can lead to their destruction. SWNTs with diameters of 1.3 nm and larger are more stable against degradation, and stability increases with diameter. The effect of diameter, defects, and exterior contamination on the inherent stability of SWNTs under electron beam irradiation is investigated