Carbon nanotubes growth by thermal chemical vapor deposition using silica and alumina as support layers and Fe as catalyst
Aguiar, Marina R.; Verissimo, Carla; Ramos, Antonio C. S.; Moshkalev, Stanislav A.; Swart, Jacobus W. Brazil
Carbon nanotubes (CNTs) have been widely produced using different synthesis methods. Chemical vapor deposition (CVD) on supported catalyst substrates has been our process choice to grow these structures. It has been shown that the CNTs growth depends on the support material. It also has been observed that surface roughness and metal particles morphology play an important role in the CNTs growth mechanism. Here we present the influence of the catalytic metal-substrate interaction on CNTs growth over Fe/SiO2/Si, Fe/Al2O3/Si, and Ni-Fe/SiO2/Si support systems. We also show an evaluation of the CNTs growth rates. Thermally oxidized n-Si (100) wafers have formed the SiO2 substrate. Dc magnetron sputtering on the same type of silicon wafers has produced the Al2O3 substrate. Thin metal catalyst films of iron and nickel/iron have been deposited onto SiO2 and Al2O3 support substrates by electron beam process. The CVD processes have been performed on a horizontal tubular quartz furnace under atmospheric pressure, using a mixture of methane and hydrogen gases at temperatures as high as 950°C. The oxide layers are analyzed by atomic force microscopy (AFM) and the roughness of Al2O3 has presented two orders of magnitude higher than SiO2. The as-synthesized products have been characterized by high resolution scanning and transmission electron microscopy and Raman spectroscopy. The results show that different substrates can strongly influence the CNTs growth behavior.