Continued Growth of Single-Walled Carbon Nanotubes

Abstract

We demonstrate the continued growth of single-walled carbon nanotubes (SWNTs) from ordered arrays of open-ended SWNTs in a way analogous to epitaxy. Nanometer-sized metal catalysts were docked to the SWNT open ends and subsequently activated to restart growth. SWNTs thus grown inherit the diameters and chirality from the seeded SWNTs, as indicated by the closely matched frequencies of Raman radial breathing modes before and after the growth.

Chirality-controlled synthesis of single-wall carbon nanotubes using vapour-phase epitaxy

“…Unfortunately, attempts to control the size of the catalysts in hope of achieving chirality-controlled nanotube growth have not been successful 21 . Nanotube 'cloning' has been studied with 22,23 and without 24 metal catalyst particles showing various degree of success; however, controlled synthesis of nanotubes with predefined chiralities has not been achieved. In contrast, vapour-phase epitaxy (VPE) such as molecular beam epitaxy and metal organic CVD has long been used by the semiconductor industry to grow two-dimensional epitaxial films, which can preserve the crystalline structure of the starting substrate.…”

Density functional theory and tight binding-based dynamical studies of carbon metal systems of relevance to carbon nanotube growth

“…These clusters catalyse regrowth at the end of the SWNT seed. Although it has been shown [4] that the distribution in seed chiralities affects those of the regrown SWNTs, it is not known if chirality is controlled at the individual SWNT level.…”

“…For example, previous TBMC simulations at 1000 K showed that Ni atoms that are uniformly distributed over an SWNT wall aggregate and diffuse to the open end of the SWNT, where they remain for the remainder of the simulation [14]. This is important to SWNT regrowth where, as discussed above, one evaporates metal atoms into the growth chamber before heating and introducing feedstock for regrowth [4]. In this contribution we present results when the Ni atoms are not initially uniformly distributed over the SWNT surface, which is relevant to the regrowth experiments since heating of the system is expected to lead to aggregation of clusters at different places in the chamber, e.g., on the SWNT walls, before they diffuse to the SWNT end.…”

“…Two methods that have shown potential for selective chiral growth are rapid heating based on cobalt-molybdenum (Co:Mo) catalysts [3] and SWNT regrowth [4] (also called seeded growth). In the former method the alloy particles are rapidly heated while carbon feedstock is introduced for SWNT Nano Res (2009) 2: 774 782 growth.…”

“…In the second method [4], SWNTs are used as seeds to grow longer SWNTs. SWNTs are purified and carefully cut (to expose open SWNT ends) before metal atoms are evaporated into the reaction chamber.…”