CVD catalytic growth of single-walled carbon nanotubes with a selective diameter distribution

Abstract

Thermal pyrolysis chemical vapor deposition growth of single-walled carbon nanotubes (SWNTs) was demonstrated by using catalytic pads of nickel (3∼4 nm) and SiO 2 (100 nm) deposited by electron-beam evaporation in sequence on the thermal silicon oxide substrate. The diameters of SWNTs on the samples with upper SiO 2 layer of different deposition rates were characterized by atomic force microscopy (AFM) and micro-Raman spectroscopy. It was observed that the average diameter and density of SWNTs increased as the deposition rate of upper SiO 2 layer increased. The differences of the SWNTs diameter distribution were attributed to the differences in the curvature of the SiO 2 porous structure deposited with different deposition rates. The high-resolution transmission electron micrographs and the corresponding diffractogram showed that SWNTs with diameter as low as 0.51 nm could be found and the AFM measurements revealed that a high percentage (∼ 70%) of SWNTs of diameters lower than 1.0 nm was achieved by upper SiO 2 layer deposition rate of 0.5 Å/s, whereas bundles of SWNTs were found with higher SiO 2 deposition rates.