Lateral growth of single wall carbon nanotubes on various substrates by means of an "all-laser" synthesis approach

We report on the use of a newly developed "all-laser" process for the growth of single wall carbon nanotubes (SWCNTs) onto various types of substrates, ranging from highly oriented pyrolytic graphite (HOPG) to thermally oxidized silicon or SiN free-standing membranes. The "all-laser" process uses the same UV laser (KrF) to deposit, in a first step, the CoNi catalyst nanoparticles on the substrates and, in a subsequent step, to grow the SWCNTs from the laser ablation of a pure graphite target. It is found that even if the SWCNTs grown onto the various substrates generally share the common feature of exhibiting a lateral growth, their structural packing, morphology and orientation are definitely substrate dependent. Indeed, while highly oriented and straight nanotubes (of ∼1 nm-diam.) were found to self-organize into 2D-planar bundles onto HOPG, they tend to rather form a random network of 3D-bundles of SWCNTs (∼10-20 nm-diam.) on the other substrates. These results demonstrate that by combining the latitude of the "all-laser" process with the appropriate substrate, various SWCNT nanostructures can be achieved.