Effect of catalyst thickness and plasma pretreatment on the growth of carbon nanotubes and their field emission properties

We demonstrated that the diameter and the density of carbon nanotubes (CNTs) which had a close relation to electric-field-screening effect could be easily changed by the control of catalytic Ni thickness combined with NH3 plasma pretreatment. Since the diameter and the density of CNTs had a tremendous impact on the field-emission characteristics, optimized thickness of catalyst and application of plasma pretreatment greatly improved the emission efficiency of CNTs. In the field emission test using diode-type configuration, well-dispersed thinner CNTs exhibited lower turn-on voltage and higher field enhancement factor than the densely-packed CNTs. A CNT film grown using a plasma-pretreated 25 angstroms-thick Ni catalyst showed excellent field emission characteristics with a very low turn-on field of 1.1 V/microm @ 10 microA/cm2 and a high emission current density of 1.9 mA/cm2 @ 4.0 V/microm, respectively.