Ferric-sulfate-catalysed hot filament chemical vapour deposition carbon nanotubesynthesis

Abstract

This paper reports on the first use of a sulfur-containing substrate catalyst (ferricsulfate) in a hot filament chemical vapour deposition (HFCVD) reactor for carbonnanotube synthesis. The study combines three attractive features concerningcatalysis, nucleation, and morphological control of nanotube growth inthis context. First, it involves enhancement of iron’s catalysis action bysulfur, proven effective previously in a similar capacity in chemical vapourdeposition (CVD) studies not involving a hot filament. Second, it involvesreduction of an iron compound with atomic hydrogen in the HFCVD reactor,which, through production of a fine dispersion of reduced substrate ironparticles is a facilitating step in carbon nanotube nucleation. Third, forcontrol of carbon nanotube morphology, it uses the CVD variables method,which uses the inherent capabilities of changes in CVD variables to controlthe growth morphology of carbon nanotubes. It is demonstrated in thisreport that the combination of these attractive features has enabled us toproduce both randomly oriented and vertically aligned carbon nanotubes.