Experimental Demonstration of Fractal Shape Transition and Fractal Size in Ge Clusters Formation

The nucleation and growth of Ge fractal clusters in Au/Ge bilayer films have been investigated by transmission electron microscope (TEM). It is found that the fractal crystallization, the fractal shape transition, and the fractal size strongly depend on the annealing time and the films thickness ratio. The fractal formation can be explained by a random successive nucleation and growth (RSNG) model. The fractal shape transition and fractal size may be determined by the relative ration between the propagation rate of RSN process and the grain growth rate.