We report on a novel method based on a plasma pretreatment for controlled nanostructuration and patterning of iron catalyst particles from a continuous film in view of carbon nanotube growth. The effects of the hydrogen plasma conditions on the diameter and the density of the catalyst nanoparticles was studied and discussed. We were then able to propose a comprehensive mechanism for the metallic nanostructuration. We showed that as the plasma power density increases, first a reduction of the iron nanoparticle size is observed followed by for the highest plasma powers a phenomenon of alteration in the deposited film. A better control of the nucleation process and the nanostructuration were observed for low hydrogen pressures. The correlation between the plasma parameters and the obtained iron nanoparticles was established. The growth of carbon nanotubes (CNTs) was carried out on the patterned catalyst nanoparticles under CH 4 /H 2 microwave plasma. High quality double-walled and multiwalled CNTs of a diameter of about 5 nm have be obtained.
Catalysts play a key role in the growth of carbon nanotubes. The microwave plasma-assisted chemical vapor deposition (MPACVD) method is now commonly used for directional and conformal growth of carbon nanotubes (CNTs) on substrates. In this work, we report on the effect of H(2) plasma pre-treatment on the diameter and density of iron catalyst nanoparticles for different iron layer thicknesses in order to grow isolated bundles of CNTs. Atomic force microscopy shows first that as plasma power density increases, iron nanoparticle diameters decrease, which is due to the increasing of gas dissociation giving more ion bombardment energy, and second that the diameter of nanoparticles decreases with the catalyst thickness. The growth of CNT was carried out under different CH(4) concentrations for different iron film thicknesses. Transmission electron microscopy and Raman spectroscopy show that the synthesized CNT were of good quality and had an outer diameter between 5 and 10 nm.
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