Single‐walled carbon nanotube networks growth optimization

Abstract

, Phone: þ39 010 717 81 564, Fax: þ39 010 717 08 17.In recent years there have been many improvements in quality and yield of single-walled carbon nanotubes (SWCNTs) obtained by chemical vapour deposition (CVD). Mainstream in research is focused on growing thick vertically aligned forests of SWCNTs. At the same time SWCNT films -usually obtained by spraying and filtration -are one of the most promising candidates to replace indium tin oxide (ITO) as transparent electrodes in solar cells and flat displays. The main limit of those techniques is that usually carbon nanotubes (CNTs) are deposited in the form of thick bundles and are mixed with insulating molecules, such as surfactants, used to try to unbundle the CNTs in solution. Moreover, ultrasonication is in general used to help dispersion, inducing defects in the tubes; the overall effect is to considerably reduce the conductivity of such CNT films. It is our firm belief that a considerable improvement in film quality can come by directly synthesizing the networks onto the substrate via CVD, but this requires achieving a control of the density and quality of the SWCNT networks without losing the planar arrangement. We show here our latest results in enhancing the quality of SWCNT percolating network synthesis by alcohol CVD on silicon oxide substrates using cobalt and nickel acetates as precursors.

Electronic Conduction in Disordered Carbon Materials

“…CNTs have been used as transparent conductive coatings or films [Ansaldo et al 2008], and as active material for transparent and flexible transistors [Ansaldo et al 2009]. According to Ansaldo et al, SWCNT films are "one of the most promising" candidates to replace indium tin oxide (ITO) as transparent electrodes in solar cells and flat displays [Ansaldo et al 2009].…”

“…In addition, single-walled CNTs (SWCNT) produced via CVD hold much promise in producing transparent, conductive samples with fewer defects [Ansaldo et al 2009] compared to post-growth production methods. The main drawback of postgrowth techniques is that they require CNTs to be dispersed in a liquid medium, thus damaging and shortening the tubes considerably, see e.g.…”

“…Specifically, the direct (or in-situ) growth of the SWNT is performed via alcohol-based CVD, with ethanol as the alcohol. The spin-coated catalyst is also known as a pre-cursor, and consists of cobalt acetate or a mixture of cobalt and nickel acetate [Ansaldo et al 2009;2007].…”

“…Co-Ni compounds are most promising as catalysts, with relatively long and high-quality nanotubes, with the possibility to tune the production from carpet-like to isolated nanotubes [Ansaldo et al 2007]. The optimization of the CVD method is reported in [Ansaldo et al 2009].…”

“…Eight networks are prepared by Ansaldo and colleagues [Ansaldo et al 2009;2007] while five networks prepared by Lima and colleagues [Lima et al 2007]. Data for one post-grown SWNT network by Andrade and colleagues [Andrade et al 2007] is added in our analysis for comparison.…”