Effects of Ni-catalyst characteristics on the growth of carbon nanowires

Carbon nanowires (CNWs) were grown on amorphous Ni thin film catalysts in a microwave plasma-enhanced chemical vapor deposition system under a methane and hydrogen gas mixture. The resulting CNWs were found to be polycrystalline but not amorphous as commonly found elsewhere. In general, a catalyst could be seen at the tip of each CNW. However, multiple CNWs grown from a single catalyst were also regularly observed. The use of amorphous Ni thin film catalyst also resulted in the formation of an interlayer between the CNWs and the substrate. The appearance of this interlayer, however, depends on the Ni film thickness. The carbon nanowires obtained were found to exhibit an unusual microstructure in that the basal planes were perpendicular to the wire axial direction. The Raman signatures of the CNWs consist of two peaks near 1322 cm^-1 (D-band) and 1578 cm^-1 (G-band), similar to that of carbon nanotubes. The broadening of the G-band peak was found to be greater than 60 cm^-1 and the I_D/I_G ratio was found to decrease with FWHM as in a-C:H.