The growing mechanism of the CNT and the correlation between the diameters of the CNT to the particle size of the catalyst and the effect of an Al buffer layer between the active catalyst material Ni on the growth of CNT using PECVD had been studied. Using a thin layer of Al as a buffer layer between active catalyst material does produce a higher density of catalyst particles as compared to the one without Al buffer layer. However, for an increasing Al thickness with our current setup, it was observed that there is a decreasing catalytic activity. The investigation of the effect of Al/Ni binary catalyst particle distribution using Grazing Incidence Small Angle X-ray Scattering (GISAXS) is also reported.