Effects of Ni catalyst–substrate interaction on carbon nanotubes growth by CVD

Abstract An investigation of the effects of substrate type and various treatments on carbon nanotubes (CNT) growth, using an evaporated Ni thin film as a catalyst, is presented. Barrier layers of SiO 2 , Si 3 N 4 , and TiN on Si were used as substrates. The catalyst-insulating substrate systems have been processed in several gaseous atmospheres (Ar, NH 3 and H 2 ) and in the temperature range 700–900 °C, in order to obtain the most appropriate morphology, size and density of catalyst particles as seeds for the subsequent CNT growth. On this kind of substrates, the smallest nanoparticles were obtained on SiO 2 layers, in H 2 or NH 3 atmosphere even at 700 °C. However, the best vertically aligned and well-graphitized CNT resulted from the NH 3 annealing process, followed by the CNT deposition at 900 °C in C 2 H 2 and H 2 . On TiN conducting substrates, the best vertically aligned CNT were deposited using a shorter annealing step and a deposition process at reduced pressure. The samples were characterized by means of scanning electron microscopy (SEM) and Raman spectroscopy analysis.