Formation of fractal islands on nonlattice substrates

A Monte Carlo study on the formation of fractal islands on nonlattice subst rates is presented. The islands, including disc aggregates and single discs , perform two-dimensional diffusion along four directions with different di ffusion step lengths and rigid rotation about their centers of mass on a no nlattice square with periodic boundary conditions. It is found that the fra ctal dimension of the ramified islands is almost independent of the diffusi on step length, rigid rotation angle, and disc size. However, the fractal d imension increases linearly with the surface coverage. Our simulation resul ts are in good agreement with the previous experimental findings of the agg regation of the silver atomic islands on silicone oil surfaces. [S0163-1829 (99)14303-0].