Millimetre-scale growth of single-wall carbon nanotube forests using an aluminium nitride catalyst underlayer
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MRS Advances © 2018 Materials Research Society DOI: 10.1557/adv.2018.653
Millimetre-scale growth of single-wall carbon nanotube forests using an aluminium nitride catalyst underlayer Takashi Tsuji1, Naoyuki Matsumoto1*, Hirokazu Takai2, Shunsuke Sakurai1, Don N. Futaba1* 1
CNT –Application Research Centre, National Institute of Advanced Industrial Science and Technology (AIST), Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki, 305-8565, Japan
2
ZEON Corporation, 1-6-2 Marunouchi Chiyoda-ku, Tokyo 100-8246, Japan
ABSTRACT
We have demonstrated the high yield (~900 μm) and highly single-wall selective (>95%) growth of carbon nanotube (CNT) forest using aluminium nitride (AlN) as a catalyst underlayer. Such high efficiency and single-wall selectivity have not been previously reported using this underlayer system. Evaluation with transmission electron microscopy showed that the average diameter of the grown carbon nanotubes was ~3.0 nm, which is similar to those grown on alumina underlayers. In addition, characterization of the catalyst/underlayer system using atomic force microscopy and X-ray photoelectron spectroscopy suggests that neither Ostwald ripening along the surface nor catalyst subsurface diffusion into the AlN underlayer are severely occurring at the growth temperature, leading to the creation of the stable and dense small nanoparticle array to achieve an efficient growth of single-wall CNTs.
INTRODUCTION Chemical vapour disposition (CVD) is by far the most common way to synthesize long and pure single-wall carbon nanotubes (SWCNTs) from catalyst nanoparticles supported on a substrate. Within this system, crowding of the individual SWCNTs results in a vertical assembly, commonly referred to as a “forest,” “carpet,” or “array” [1–3]. Growth of SWCNTs in this manner results in CNTs of high purity [2] and specific surface area [4,5], which is very useful for applications spanning composite materials [6], pastes [7], and super-capacitor electrodes [8]. One commonality among the numerous reports of efficient SWCNT growth (i.e. ~hundreds of micrometres to millimetre-scale) is the essential use of an alumina (Al2O3) catalyst underlayer which
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aids in the formation of a stable array of small and dense catalyst nanoparticles. Sputtering and e-beam deposition is by far the most common method of catalyst deposition, and a number of groups have reported the growth of millimetre-scale CNT forests through these means [2,3,9–12]. Moreover, the porosity of the Al2O3 underlayer, which differs based on deposition methods, has been reported to greatly affect the Ostwald ripening of iron (Fe) catalyst, which results in the extension of the catalyst lifetime. This extended lifetime is crucial for the realization of tall SWCNT forests [13]. With the recent exception of magnesia (MgO) [14],
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