The Role of the Adatom Diffusion in the Tungsten Fuzz Growth

The model of the tungsten fuzz growth due to adatom diffusion is considered. Adatoms are created by helium ions bombarding the fuzz surface and diffuse along the fiber in both directions (towards the top and bottom). Only if there is an external force making movement towards the top preferential, the fiber can grow. We assume that this force is due to change of the surface binding energy of the adatom while it moves to a fiber top. The molecular dynamics (MD) simulations were performed to determine the surface binding energy dependence on the surface curvature. Adatom flow and a fiber length change were obtained by using this dependence. A square root time dependence of the fiber length was found. Numerical estimates are consistent with the experimental data.