Improving quality of single-walled carbon nanotube networks

Single-walled carbon nanotubes (SWCNTs) are one of the most interesting alternatives to indium tin oxide for the fabrication of transparent conductive films. SWCNT percolating networks have been produced by a variety of different methods, mainly by spraying or filtration of solutions, but, unfortunately, suspending CNTs in liquid requires the use of ultrasound and surfactants. While sonication reduces bundling, it increases the number of defects and also shortens CNTs. Moreover, surfactants are difficult to remove and tend to create an insulating layer between the CNTs and between CNTs and leads. The overall effect is to reduce the global conductivity of the CNT films. It is our opinion that a considerable improvement in film quality can come from a direct synthesis of the network on a flat substrate by chemical vapour deposition (CVD). The networks can then be used on the growth substrate or directly transferred onto a plastic film using techniques that avoid suspension of the CNTs in a liquid. We show here our latest results in controlling the quality of SWCNT percolating network synthesis by alcohol CVD on silicon oxide substrates using cobalt and nickel acetates as precursors, varying catalyst composition, substrate preparation and catalyst pre-treatment.