Variation in the height of carbon nanotubes (CNTs) grown has been co-related to the type of multi-barrier-layer used. Initially, various types of barrier-layers such as Al, Al2O3, Al/SiO2, Al2O3/SiO2 were prepared onto a n-type Si (100) substrate. The thickness of SiO2 was similar to 550 nm, where as, Al2O3 and Al were similar to 15 nm thick. These samples were covered with similar to 1 nm thick Fe catalyst layer. The coated samples were subjected to the thermal chemical vapor deposition (T-CVD) process. SEM analysis showed that, for Al2O3/SiO2 barrier layers, the average height of the CNTs was similar to 10 mu m, where as, for other types of samples it was less than similar to 1 mu m. To investigate this, multi-barrier layers were characterized by dynamic secondary ion mass spectrometry (D-SIMS). The observed variation in height of CNTs is attributed to the variation in diffusivity of Fe atoms into multi-barriers-layers. The results showed that, diffusion of Fe catalyst atoms could severally affect height of CNTs. (c) 2007 Elsevier B.V. All rights reserved.