Single chamber PVD/PECVD process for in situ control of the catalyst activity on carbon nanotubes growth

In this paper, we studied the effect of oxygen on the catalyst activity and related influence on the nanotubes (CNTs) growth by low-pressure/high-density plasma. CNTs were prepared using a novel single vacuum chamber reactor combining (i) plasma assisted physical vapour deposition (PVD) for catalyst deposition under O2, NH3 or Ar atmosphere with (ii) electron cyclotron resonance (ECR) C2H2/NH3 plasma enhanced chemical vapour deposition (PECVD) process for carbon nanotubes growth. The substrates are in situ prepared by controlled PVD allowing the deposition of sub-nanometric catalyst (Fe, Ni, Pd) films followed by ECR-PECVD CNTs growth. Transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) analysis of CNTs show that the volume oxidation of the nanometric catalyst particles partially inhibits the CNTs growth while the catalyst surface oxidation can be reduced by the atomic nitrogen during the PECVD process. The specially designed PVD/PECVD process preserves the catalyst from moisture contamination, reducing walls nanotube defects.