Growth of Carbon Nanotubes on Carbon/Cobalt Films with Different sp2/sp3 Ratios

The need of barrier layer such as SiO2 for carbon nanotubes (CNTs) growth limits their performance in electronic applications. In this study, conductive carbon/metal (carbon/cobalt-C:Co) composite films with the same metal content, but different sp(2)/sp(3) ratios, were deposited using dual-source filtered cathodic vacuum arc (FCVA) technique. Three different C:Co composite films were deposited at different temperatures; visible Raman spectroscopy indicates that the sp(2)-rich C:Co composite film forms at high temperature (500 degrees C), and high-resolution transmission electron microscopy (HRTEM) shows the formation of conducting graphitic-like sp(2) clusters and with Co nanoclusters embedded within them. Electrical measurement shows a significant decrease in film resistivity as sp(2)/sp(3) ratio increases. CNTs were successfully grown on the composite films by plasma-enhanced vapor deposition (PECVD) approach. Scanning electron microscopy (SEM) shows minor effect on the density of CNTs by varying the sp(2)/sp(3) ratio. The dependence of defect level of the as-grown CNTs is found to reduce as sp(2)/sp(3) ratio increases.