NUE 2003-2004

Multiwalled Nanotubes - Tip Growth Model

Thermal Chemical Vapor Deposition: The growth species is generated by dissociative adsorption of hydrocarbon on catalyst surface. Nanotubes are formed via the Vapor-Liquid-Solid (VLS) mechanism.

• Substrate with catalyst thin film
• Substrate pretreatment induces formation of nanoparticle catalyst
• Catalyst surface melting on a high temperature substrate. We propose a solid core model.

• Adsorption of hydrocarbon molecules (C₂H₂ in this case) on the catalyst surface.
• Dissociation of H atoms from the hydrocarbon molecules (dissociative adsorption).

• Diffusion of carbon into the catalyst and readsorption of the hydrocarbon on the catalyst surface.
• Saturation of carbon in catalyst particle.

Segregation of carbon to form carbon nanotubes.

No segregation directly under the core. A hollow nanotube is formed.