  Growth of carbon nanotubes (CNTs) was performed by atmospheric pressure
chemical vapour deposition (APCVD) of propane on Si(111) with a pre-treated Ni
overlayer acting as a catalyst. Prior to the growth of CNTs, a thin film of Ni
was deposited on Si(111) substrate by evaporation and heat treated at
900{\deg}C. The growth of nanotubes was carried out at 850{\deg}C using propane
as a source of carbon. Distribution of the catalyst particles over the Si
substrate was analysed before and after heat treatment by atomic force
microscopy (AFM). The X-ray diffraction (XRD) pattern of the grown material
revealed that they are graphitic in nature. Field emission scanning electron
microscopy (FESEM) was used to investigate the growth process and it was found
that a catalytic particle was always situated at the tip of the tube thus
implying a tip growth mechanism. Evidence for the presence of radial breathing
mode from multi-wall nanotubes (MWNTs) in the grown sample was obtained from
micro-Raman analysis. Finally, high-resolution transmission electron
microscopic (HRTEM) analysis confirmed that the graphene layers of the CNTs are
well ordered with typical 0.34 nm spacing.
