ABSTRACTCarbon nanotubes are excellent field emitters due to their high aspect ratios and small radii of curvature. These properties of the nanotubes offer tremendous possibilities for the realization of field emission devices. For the realization of the field emission devices controlled placement and alignment of the nanotubes over the substrate surface is desirable. Furthermore, field emission of the nanotubes in cylindrical geometry has added advantages over planar geometry. But, it is difficult to grow nanotubes uniformly over non-planar substrates such as long metallic cylinders by conventional CVD techniques. In the present investigation we have adopted a very simple technique called as Cold Plasma Chemical Vapor Deposition (CP-CVD) to grow carbon nanotubes over a catalyst-supported metallic wire by resistive heating in hydrocarbon atmosphere at about 750–C. The localized dissociation of the hydrocarbon gas over metallic wire allows well controlled growth of the nanotubes. The field emission performance of these nanotube coated wires was measured in a cylindrical geometry where the aluminum tube was used as an anode. Emission site density is found to be the most important parameter to control the field emission performance. Comparisons of the field emission properties were made using nanotubes grown in different hydrocarbon gases such as methane and acetylene. The effects of other parameters, such as growth time, was also investigated.
