Controlled CVD‐growth of multiwalled CNTs

Many applications of carbon nanotubes (CNTs) require a material with defined properties, however most synthesis routes yield CNTs of varying purity, structure, diameter, and length. Chemical vapor deposition (CVD) allows a good control over the CNTs synthesis and leads to promising results, however the effect of many parameters remains unclear. In order to improve this situation a comprehensive study was carried out under highly controlled conditions. The used CVD reactor was capable to perform deposition processes with temperature deviations smaller than 1°K. The substrates were patterned Fe films with a thickness below 10 nm on silicon/siliconoxide. The effects of the conditioning of the catalyst prior to growth, growth temperature, and growth time were investigated. The synthesis in a hydrogen/acetylene atmosphere yielded pure multi‐walled CNTs with diameters between 10 – 20 nm. The length of the CNTs was accurately controlled by the growth time. The density of the CNTs can be varied by the preconditio...