Effect of entrapped Ni nanoparticles on the electrical conductivity and current-induced breakdown of MWCNTs

Despite many reports on electrical characteristics of carbon nanotubes and the role of defects on their electrical behavior, no special study has been done to understand the influence of entrapped catalyst nanoparticles on the electrical characteristics of CNTs. Since entrapment of Catalytic nano particles within the structure of nanotubes is inevitable in CVD and PECVD growth methods, it is appriciable to realize the effect of these nano-clusters on the electrical parameters of CNTs. Here, we investigated the effect of entrapped Ni nano-catalysts on the resistance and breakdown of MWCNTs grown by the DC-PECVD method. The studied nanotubes ruptured in a few seconds while carrying electric current with current densities lower than that theoretically predicted for ideal CNTs. We demonstrate that entrapped Ni nano particles have the main role in early structural breakdown due to their catalytic behavior. Raman Spectroscopy, transmission electron microscopy and energy dispersive X-ray spectroscopy analyses are exploited to corroborate the existence of Ni nano-clusters and their effects on electrical behavior of CNTs. In addition to undesirable latitudinal rupture of CNTs, Ni grains have the capability to unzip CNTs along their axes in the case of applying unidirectional electric field.