Vacuum Electron-Beam Evaporation of Fe Nanocrystals on Si₃N₄ Buffer Layer for Carbon Nanotube Growth

Vacuum electron-beam evaporated iron nanocrystal is used for the growth of carbon nanotubes. Atomic force microscopy and Raman scattering studies reveal the formation of beta-iron silicide islands on bare silicon substrate after annealing at 700°C in N₂ ambient. In order to eliminate the influence of iron-silicon interaction, Si₃N₄ buffer layer with the thickness of 80 nm is used. This technical route prevents effectively the formation of iron silicide and improves the quality of the iron nanocrystals. Using these iron nanocrystals with high density (about 7 x 10¹⁰/cm²) as catalyst, high-density multiwall carbon nanotubes are synthesized on Si₃N₄/Si substrate.