The influence of the substrate on the growth of carbon nanotubes from nickel clusters—an investigation using STM, FE-SEM, TEM and Raman spectroscopy

Chemical Vapour Deposition (CVD) is now a well-established route to the growth of carbon nanotubes (CNT). Generally, a transition metal such as nickel dispersed as clusters on a nonreactive substrate acts as a catalyst for growth from carbon-bearing gases such as acetylene. While the diameter of the tubes is closely linked to the size of the metal clusters, the nature of the substrate itself influences the size and size distribution of the clusters themselves. Using Scanning Tunnelling Microscopy (STM) to study the clusters and high resolution Field Emission Scanning Electron Microscopy (FE-SEM) to study the resultant nanotubes, we show that nickel clusters created on TiN-coated SiC substrates have a much smaller size distribution than MoSi2-coated SiC substrates. This is reflected in the nanotube diameter after CVD growth. Raman spectroscopy and Transmission Electron Microscopy has also been used to provide further data on the nature of the nanotubes and clusters grown on these substrates.