A Simple Combinatorial Method Aiding Research on Single-Walled Carbon Nanotube Growth on Substrates

Abstract

Establishing fabrication methods of carbon nanotubes (CNTs) is essential to realize many applications expected for CNTs. Catalytic growth of CNTs on substrates by chemical vapor deposition (CVD) is promising for direct fabrication of CNT devices, and catalyst nanoparticles play a crucial role in such growth. We have developed a simple method called ''combinatorial masked deposition (CMD)'', in which catalyst particles of a given series of sizes and compositions are formed on a single substrate by annealing gradient catalyst layers formed by sputtering through a mask. CMD enables preparation of hundreds of catalysts on a wafer, growth of single-walled CNTs (SWCNTs), and evaluation of SWCNT diameter distributions by automated Raman mapping in a single day. CMD helps determinations of the CVD and catalyst windows realizing millimeter-tall SWCNT forest growth in 10 min, and of growth curves for a series of catalysts in a single measurement when combined with realtime monitoring. A catalyst library prepared using CMD yields various CNTs, ranging from individuals, networks, spikes, and to forests of both SWCNTs and multi-walled CNTs, and thus can be used to efficiently evaluate self-organized CNT field emitters, for example. The CMD method is simple yet effective for research of CNT growth methods. #

Current understanding of the growth of carbon nanotubes in catalytic chemical vapour deposition

“…catalysts presenting a gradient of iron thickness, Hasegawa et al [319] evidenced that millimetre-tall VACNT forests can be grown without addition of water if the carbon precursor supply is set below a certain limit in order to retain an active catalyst; water only extends the catalyst lifetime when an excess precursor supply is used. They also found water addition to widen the window of catalyst thickness for VACNT growth toward higher thicknesses and to suppress nanotube growth from the smallest catalyst particles [299].…”

“…notably reported that the addition of water to ethylene degrades the quality of CCVD-grown SWCNTs [299]. Similarly, Gao et al [279] found that using an oxygen-containing precursor such as ethanol yielded a higher linear density of defects than using methane.…”

Growth of carbonaceous nanomaterials over stainless steel foams. Effect of activation temperature

“…However, these systems present problems related to the preparation of long term stable coatings [9][10]. Frequently, the deposition of the catalytic layer over the surface of metallic substrate is carried out by means of a washcoating stage, requiring this step a cautious attention, especially in the case of complex geometries, like of that of foams or cloths [11][12][13][14][15][16].…”

A jellium model of a catalyst particle in carbon nanotube growth

“…1 For electronics, even presently high price of the CNT (∼1k $/g) is not considered as an obstacle. 2 What still remains a challenge is the practical control of the single-walled CNT symmetry type, the chirality (n, m).…”