Alan M. Cassell

The synthesis of massive arrays of monodispersed carbon nanotubes that are self-oriented on patterned porous silicon and plain silicon substrates is reported. The approach involves chemical vapor deposition, catalytic particle size control by substrate design, nanotube positioning by patterning, and nanotube self-assembly for orientation. The mechanisms of nanotube growth and self-orientation are elucidated. The well-ordered nanotubes can be used as electron field emission arrays. Scaling up of the synthesis process should be entirely compatible with the existing semiconductor processes, and should allow the development of nanotube devices integrated into silicon technology.

The synthesis of bulk amounts of high quality single-walled carbon nanotubes (SWNTs) is accomplished by optimizing the chemical compositions and textural properties of the catalyst material used in the chemical vapor deposition (CVD) of methane. A series of catalysts are derived by systematically varying the catalytic metal compounds and support materials. The optimized catalysts consist of Fe/Mo bimetallic species supported on a novel silica−alumina multicomponent material. The high SWNT yielding catalyst exhibits high surface-area and large mesopore volume at elevated temperatures. Gram quantities of SWNT materials have been synthesized in ∼0.5 h using the optimized catalyst material. The nanotube material consists of individual and bundled SWNTs that are free of defects and amorphous carbon coating. This work represents a step forward toward obtaining kilogram scale perfect SWNT materials via simple CVD routes.

Carbon nanotubes (CNTs), due to their unique electronic and extraordinary mechanical properties, have been receiving much attention for a wide variety of applications. Recently, plasma enhanced chemical vapour deposition (PECVD) has emerged as a key growth technique to produce vertically-aligned nanotubes. This paper reviews various plasma sources currently used in CNT growth, catalyst preparation and growth results. Since the technology is in its early stages, there is a general lack of understanding of growth mechanisms, the role of the plasma itself, and the identity of key species responsible for growth. This review is aimed at the low temperature plasma research community that has successfully addressed such issues, through plasma and surface diagnostics and modelling, in semiconductor processing and diamond thin film growth.