Effects of diffusion barriers on the growth and field emission properties of carbon nanotubes using copper catalyst

Copper is a good catalyst besides Fe, Co, Ni for carbon nanotubes (CNTs) growth in field emission display application, because the emission properties of as-grown CNTs on glass substrate afford low threshold field, high current density, and uniformity. Growing carbon nanotubes on glass substrate surface requires the formation of high-density catalyst nanoparticles. This, in turn, requires the minimum diffusion of catalyst into the substrate at the growth temperature for carbon nanotubes. In this work, four metals (W, Ni, Cr and Ti) as the diffusion barrier have been optimized and examined for growing carbon nanotubes on glass substrate. The bilayer films were annealed at 550 degrees C in hydrogen gas for few minutes to form nanoparticles to grow CNTs under the atmosphere of C2H2/H-2 by chemical vapor deposition (CVD) method. With an optimized barrier layer (Ti, or W), carbon nanotubes with excellent adhesion to the substrate and good field emission properties have also been achieved.