Effects of Fe film thickness and pretreatments on the growth behaviours of carbon nanotubes on Fe-doped (001) Si substrates

Transmission electron microscopy (TEM), atomic force microscopy (AFM) and scanning electron microscopy (SEM) are used to investigate the effects of Fe film thickness and pretreatment conditions on the growth behaviours of carbon nanotubes on the Fe-deposited Si (001) substrates. The Fe films are deposited for 20 s-20 min by pulse-laser deposition. SEM results show that the growth characteristics of carbon nanotubes are strongly dependent on the Fe film thickness and pretreatment conditions. It is shown that the pretreatments at 800degreesC (and also chemical vapour deposition growth) cause the continuous Fe films to be broken up into nanoparticles (8-50 nm across) and discontinuous islands (100 nm-1.1 mum in size). It is also shown that the Fe nanoparticles are essentially required for the formation of aligned carbon nanotubes. Furthermore, for the Ar-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 TEM and SEM results, the pretreatment atmosphere dependence of the growth behaviours of carbon nanotubes is discussed.