Abstract
Fe and Ni organic solutions were used as the catalyst source for growing carbon nanotubes. The effect of concentrations of the organic solution and the composition of the gases used in pretreatment on the resulted carbon nanotubes were studied. The carbon nanotubes were examined by electron microscopy and characterized by their field emission properties and Raman spectra.Carbon nanotubes can grow on iron particles formed by reduction in 10% hydrogen-nitrogen or ammonia gas. By mixing the organic iron solution with photo-resist materials in a standard lithographic patterning process, the patterned organic iron film can be formed which has been used to grow carbon nanotubes successfully.Organic nickel films can be more easily reduced than organic iron films to form small metal particles. Carbon nanotubes were even grown successfully on the organic nickel film without pre-reduction by heating with 700 W microwave in 550 torr 300 sccm 1:1 mixture of methane for 20 minutes. The lowest concentration film (0.1M) gave the best result of small diameter (30 nm) carbon nanotubes with less carbon soot.The carbon nanotubes can grow not only upward but also downward to the Si substrate which pushed the layer of carbon nanotubes up from the substrate. A mechanism of the forming of carbon nanotubes is proposed to explain this observation.Carbon nanotubes can grow successfully on titanium coated Si substrate. The carbon nanotubes grown on Ti thin film can be turned-on at an electric field as low as 1.5 V/μm due to the better electric conductivity of titanium.