Fractality aspects during agglomeration of solid-phase-epitaxy Co-silicide thin films

Morphology changes of thin CoSi2 films close to the agglomeration threshold have been investigated by in situ scanning tunneling microscopy. Films prior to agglomeration reveal a strong morphology anisotropy where depending on direction the roughness correlation g(r) changes from logarithmic [g(r)∼ln r] to power law [g(r)∼r2c with c≈0.78] at short lateral length scales (r⩽30 nm). Such an anisotropy reflects the complex nature of diffusion process associated with the original anisotropic substrate surface and the formation of pinhole networks. Annealing above the agglomeration threshold (>600 °C), the pinhole network becomes connected breaking the CoSi2 film into aggregates with a two-dimensional fractal dimension D≈1.66 which is close to predictions of diffusion limited aggregation within the mean field theory prediction D=(d2+1)/(d+1) for d=2, and invasion percolation models