2 research outputs found
Gas flow-directed growth of aligned carbon nanotubes from nonmetallic seeds
Kite growth is a process that utilizes laminar gas flow in chemical vapor
deposition to grow long, well-aligned carbon nanotubes (CNTs) for electronic
application. This process uses metal nanoparticles (NPs) as catalytic seeds for
CNT growth. However, these NPs remain as impurities in the grown CNT. In this
study, nanodiamonds (NDs) with negligible catalytic activity were utilized as
nonmetallic seeds instead of metal catalysts because they are stable at high
temperatures and facilitate the growth of low-defect CNTs without residual
metal impurities. Results demonstrate the successful growth of over
100-m-long CNTs by carefully controlling the growth conditions.
Importantly, we developed an analysis method that utilizes secondary electron
(SE) yield to distinguish whether or not CNTs grown from metal impurities. The
absence of metallic NPs at the CNT tips was revealed by the SE yield mapping,
whereas the presence of some kind of NPs at the same locations was confirmed by
atomic force microscopy (AFM). These results suggest that most of the aligned
CNTs were grown from nonmetallic seeds, most likely ND-derived NPs, via the
tip-growth mode. Structural characterizations revealed the high crystallinity
of CNTs, with relatively small diameters. This study presents the first
successful use of nonmetallic seeds for kite growth and provides a convincing
alternative for starting materials to prepare long, aligned CNTs without metal
impurities. The findings of this study pave the way for more convenient
fabrication of aligned CNT-based devices, potentially simplifying the
production process by avoiding the need for the removal of metal impurities.Comment: Accepted version. Main manuscript: 26 pages, 6 figures. Supporting
information: 8 pages, 9 figure
Thermal defect healing of single-walled carbon nanotubes assisted by supplying carbon-containing reactants
We experimentally investigated the effect of carbon-containing reactants (C2H2) on healing the defects in single-walled carbon nanotubes (SWCNTs) by thermal processes at high temperatures (∼1100 °C). Introducing C2H2 notably improved the crystallinity of healed SWCNTs compared with the thermal process in Ar ambient without C2H2. The defect healing rate increased with increasing C2H2 partial pressure, and the healing effect of C2H2 was more remarkable for relatively thinner SWCNTs (<1.1 nm). Combined with the relevant theoretical work reported previously, we propose a healing model in which C2H2 helps to heal the vacancy defects and increases the healing rate at high temperatures.This is the version of the article before peer review or editing, as submitted by an author to Applied Physics Express. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at https://doi.org/10.35848/1882-0786/acaaec