Density enhancement of aligned single-walled carbon nanotube thin films on quartz substrates by sulfur-assisted synthesis.

The density of the aligned single-walled carbon nanotubes (SWNTs) grown on quartz substrates is an important factor for the performance of fabricated electronic devices. It was discovered that the addition of a sulfur-containing compound (thiophene) to the reaction mixture improved the density of SWNTs by a factor of 2 or more, from approximately 2-4 SWNTs/microm to 6-8 SWNTs/microm under similar growth conditions. It was also observed that along with the increase in nanotube density, the cleanness of the samples improved as well. These effects were demonstrated over a large range of growth conditions, indicating that the addition sulfur makes the growth processes more favorable for the nucleation and growth of aligned SWNTs.