The effect of Ni catalytic nanoparticle on the growth of carbon nanotubes: A perspective from nanotribological characterization

Characteristics of section structure, surface morphology, topography and tribology of catalyst nanoparticles synthesized with a microwave plasma chemical vapor deposition system on Ni/TaN/Si substrate are achieved by means of scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), ex situ atomic force microscopy (AFM), and nanoscratch techniques. In this study, we propose that the effect of catalyst nanoparticles on the growth of carbon nanotubes (CNTs) can be characterized by its tribological behavior. The results show that the temperature and the plasma treatment resulted in melting and roughening of the substrate surface, and promoted the formation of uniformly separated metal particles at 550 °C. This is due to the catalyst conglomerate forming particles with more uniform size under higher temperature. Our nanoscratch analysis indicates that the coefficient of friction of Ni nanoparticles/TaN/Si system increases from 0.77 to 1.2 while the pretreatment temperature increases from 450 °C to 550 °C. Furthermore, the scratch wear depth under ramping load show that higher pretreatment temperature leads to Ni nanoparticles with higher shear resistance, which enhances the well-aligned CNTs. These findings reveal that the role of pretreatment catalytic nanoparticles on the growth of CNTs can be identified by its nanotribological behavior.