Effects of catalyst pre-treatment on the growth of single-walled carbon nanotubes by microwave CVD

Layers of carbon nanotubes were deposited by microwave CVD on oxidized silicon substrates coated with Al–Fe–Mo catalyst films. To achieve a tube growth at about 973 K, the ion bombardment of the catalyst surface has to be avoided. The appropriate pre-treatment of the substrates is essential for the deposition of single-walled carbon nanotubes. Annealing in air is preferable to the frequently used reducing pre-treatment prior to the deposition as a higher area density of the tubes and a better reproducibility of deposition can be obtained. To figure out this finding, selected samples were investigated by analytical transmission electron microscopy and Raman spectroscopy. It is shown that the pre-treatment has a strong effect on the size and distribution of the catalyst particles.