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The role of the electric field for a vertical direction growth of the carbon nanotubes (CNT) will be analyzed and a field controlled growth model is proposed. The results suggested 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 ion implantation fixed the distribution of the concentration gradient of carbon atoms across the nanocatalyst particle, i.e. the direction and the growth velocity of the CNTs, by lessening 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 field emission properties of the cathodes made from vertically aligned CNTs on top of metallic tip substrates were studied. The results will be shown and analyzed in particular for the current emission stability and lifetime within different array structures and vacuum environments.