Different effects of substrates on the morphologies of single-walled carbon nanotubes

In this work, different effects of substrates on the morphologies of single-walled carbon nanotubes (SWNTs) are studied. SWNTs were produced by floating catalytic chemical vapor deposition using CH₄ as carbon source gas and Ar as carrier gas. Then the SWNTs were deposited on lithography-patterned different substrates. The as-grown SWNTs at the boundaries between SiO₂ and metal were characterized by scanning electron microscopy, atomic force spectroscopy and Raman spectroscopy. It is found that SWNTs deposited on low-conductivity substrates trend to have curved morphologies and some of them form rings, while SWNTs deposited on metal substrates remain straight and orientated. The mechanism of these effects was also discussed, which is closely related to the thermal conductivities and the principle of energy dissipation.