Molecular dynamics simulation of physical vapor deposition of metals onto a vertically aligned single-walled carbon nanotube surface

Behaviors of nickel and gold clusters deposited onto a vertically aligned single-walled carbon nanotube film (VA-SWCNT) were investigated by molecular dynamics simulation methods. Brenner potential was applied for carbon–carbon, and bond-order potential was applied for metal–metal and carbon–metal interactions. Their parameters of gold–gold and carbon–gold were derived by density functional theory calculations. After metal clusters were fully annealed, they were deposited onto the flat nanotube surface with small evaporation energy. Nickel clusters spread over the surface; on the other hand, the gold clusters sometimes formed a grain-like structure, especially when they formed a large cluster before arriving at the surface. When another CNT was placed on the vertically aligned surface, nickel clusters spread and formed a smooth surface, as in the case of a VA-SWCNT film; however, gold clusters could not spread but formed a grain-like structure. This result is in good agreement with the experimental and indicates the mechanism for forming a grain-like structure on a VA-SWCNT. To avoid the formation of a grain-like structure on the surface of a SWCNT, the deposition should be carried out under a high vacuum condition and at a low deposition rate for preventing clustering as it obstructs formation of a flat surface.