Catalyst-assisted vertical growth of carbon nanotubes on Inconel coated commercial copper foil substrates versus sputtered copper films

We have compared the growth of multi-walled carbon nanotubes using thermal chemical vapor deposition (CVD) on two types of substrates, copper foils and sputtered copper films. In both cases an initial 12 nm thin film of Inconel is first deposited on the Cu before growing the nanotubes. The Inconel thin film can act as both a catalyst for nanotube growth as well as a support for the additional Fe catalyst that is supplied in the form of ferrocene during CVD growth. The surfaces of the underlying copper substrates are very different and play a role in the resulting carbon nanotube density. A quantitative analysis of the density and alignment of the resulting carbon nanotubes using scanning electron microscopy shows that the smooth surface of the sputtered copper substrate leads to improvement in vertical growth and density of nanotubes as opposed to the much rougher electropolished Cu foil. We show that this is related to the differences in catalyst islands distributions and graphitic crystallinity seen on the surfaces of the two types of substrates after heating the samples in the CVD chamber. This demonstrates that the surface of the starting substrate plays an important role in the subsequent catalyst surface distribution and therefore the resulting nanotube density.