The multiple cluster growth of ultra-thin films on a hexagonal substrate with fractal, dendritic and compact
morphology has been studied by computer simulation. The influence of the different diffusion processes along island
edges on the island shape has been investigated. The results show that the anisotropic corner diffusion induces the
dendritic growth, and the anisotropic step diffusion can promote the anisotropic growth and cause the ramified islands
growing in three directions. In the case of compact growth, the island shape is mainly determined by the anisotropic
corner crossing process. The nonuniform distribution of the multiple cluster formation can be described quantitatively
by multifractal. With patterns changing from fractal to compact islands, the width and height of the bell-like or
hook-like multifractal spectra increase, while the top f(α) decreases.