Reactive wetting- and dewetting-induced diffusion-limited aggregation

Diffusion-limited-aggregation-like fractals, formed by the wetting of an eutectic SnPb alloy ball on an Au/Cu/Cr multilayered thin film and the dewetting of SnPb from the Cr surface after the Au/Cu thin film underneath the wetting cap was consumed, have been observed experimentally. The wetting-formed fractal is inside the precursor of the SnPb wetting cap, while the dewetting-formed fractal sits around the center of the SnPb cap. A unique characteristic of the former is that its growth direction is opposite to the wetting direction of the SnPb. More interestingly, the latter seems to be a reverse process of the regular fractal formation, and it ends up with a diffusion-limited-aggregation-like pattern. The dimensions of the two fractal patterns are measured to be [formula presented] [formula presented] Their formation mechanisms are discussed in terms of diffusion-limited aggregation and its reverse process, respectively.