Freestanding vertically aligned arrays of individual carbon nanotubes on metallic substrates for field emission cathodes

Direct growth of individual and vertically aligned carbon nanotubes (CNTs) onto a metallic tip apex using a two-chamber radio-frequency plasma-enhanced chemical vapor deposition is reported. Individual $\mathrm{Ni}$ nanocatalysts, obtained by a sol–gel combustion technique, were dots for the nucleation of individual CNTs that were freestanding, clean, and vertically aligned by the presence of a controlled applied field. The arrays of CNTs obtained, having a low-density spatial distribution to avoid mutual electrostatic field screening, gave uniform stable overall field emission patterns after a conditioning process. Effective total current densities up to $1\mathrm{A}∕{\mathrm{cm}}^2$ can be extracted.