Measure of the Fractal Dimension of Islands in Epitaxial Thin Film Growth

We measure the fractal dimension of islands during epitaxial thin-film growth. The fractal dimension appears to depend on the ratio of the diffusion-to-deposition rates D/F and on the coverage of adatoms. For sufficiently large D/F , i.e., D/F ≥ 10, and for sufficiently low coverages, the fractal dimension appears to be similar to that of the diffusion-limited aggregation (DLA) while for smaller D/F and low coverages it is found to be much smaller than the DLA fractal dimension. As the coverage is increased, the fractal dimension is found to increase monotonically up to the substrate dimension at the coverage of about 0.6 monolayer. The rate-equation solutions obtained using the measured fractal dimensions are also discussed.