Effects of Fe film thickness and ammonia on the growth behavior of carbon nanotubes grown by thermal chemical vapor deposition

The growth behaviour of carbon nanotubes on the Fe-deposited Si (001) substrates by thermal chemical vapor deposition (CVD) has been investigated using transmission electron microscopy (TEM), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The Fe films are deposited for 20 s - 20 min by pulse-laser deposition. SEM results show that the growth characteristics of carbon nanotubes strongly depend on the Fe film deposition time. TEM and SEM results show that the pretreatment annealing at 800°C causes the continuous Fe films to be broken up into nanoparticles 8 - 50 nm across and discontinuous islands 100 nm - 1.1 μm in size. It is shown that the Fe nanoparticles are essentially required for the formation of aligned carbon nanotubes. SEM results show that the growth behaviors of carbon nanotubes are strongly dependent on the pretreatment atmospheres. In addition, for the Ar gas-pretreated sample, a carbonaceous layer is formed near the surface region. TEM results show direct evidence that a base growth mode is responsible for the growth of carbon nanotubes in the present work. Based on the microscopy results, the pretreatment condition dependence of the growth behaviors of carbon nanotubes is discussed.