Curvature effect on the surface diffusion of silver adatoms on carbon nanotubes: Deposition experiments and numerical simulations

The cluster formation of silver adatoms on carbon nanotubes (CNTs) is investigated to infer the curvature effect on surface diffusion. By analyzing the cluster density as a function of the deposition time t for different diameters dc of CNTs, we obtain the scaling form for describing the curvature effect on surface diffusion in the first-order approximation. We find that the curvature effect on the surface diffusion can well be described by using the relation between the deposition time t and the scaled deposition time τ in the form of τ∼t dc -z, with z being the exponent characterizing geometric properties of CNTs and the nanotube helicity. The value of z for the armchair-type CNT is larger than those for the zig-zag type and the chiral-type CNTs. The scaling form is further demonstrated and verified by numerical simulations, and is explained by the two-dimensional random walk model. Our study may provide a potential application of determining the armchair-type single-wall CNT from measuring the value of z.