Nanoparticles of polycrystalline Ge have been grown in a freshly cleaved single crystal NaCl (100) substrate, starting from Au/Ge bilayer films prepared using the evaporation method during annealing. The experimental results indicate that fat fractal Ge patterns can be formed in Au/Ge bilayer films by annealing at 100°C for 60 and 70 min. Here, we report in detail interdiffusion assessment of nanoparticles in fat fractal patterns. The scaling exponent (or fractal dimension) of polycrystalline Ge clusters in fat fractal patterns is larger than that of the conventional diffusion-limited aggregation. The formation of fractal patterns and the perplexing scaling behaviour may result from the random successive nucleation and growth mechanism.