Direct growth of individual and vertically aligned carbon nanotubes (CNT) onto a metallic tip apex using a two-chamber radio-frequency plasma-enhanced chemical vapor deposition reactor is reported. Individual Ni nanocatalysts were the sites for the nucleation of individual CNTs that were freestanding, clean, and vertically aligned by the presence of a controlled applied field. To understand the role of the electric field during the growth of these individual vertically aligned CNTs, we have separated the plasma production from the applied electric field to the CNTs, by the use of the two-chamber reactor. Our results suggest that the growth direction is mainly related to the ion implantation of carbon species in the metal catalyst located on the top of the CNTs. In this model, the direction of ion implantation fixes the distribution of the concentration gradient of carbon atoms across the nanocatalyst particle, i.e., the direction and the growth velocity of the CNTs. Moreover, it lessens the role of surface decomposition and dissolution of the feed gas. For a polarized substrate the growth direction is then vertical to the surface. The obtained arrays of CNTs, having a low-density spatial distribution to avoid mutual electrostatic field screening, gave uniform and stable overall field emission patterns after a conditioning process. Effective total current densities up to I A/cm(2) can be extracted. (c) 2006 American Vacuum Society.