Growth of fractal patterns in ZnO films doped with Fe

ZnO films both undoped and doped with Fe were deposited on Si substrates using rf-magnetron sputtering. The results showed that fractal features were clearly exhibited in the ZnO film doped with Fe. It is proposed that the fractal aggregates were the result of cluster diffusion-limited aggregation (CDLA) of magnetic particles on the surface of the film. The fractal dimension of a main branch (D=1.47) was smaller than that expected by the CDLA model (D=1.72). In this paper the growth mechanism of the observed fractal aggregates is discussed in terms of the magnetism of FeO, nanoparticle aggregation and surface tension changes.