Fractal-like Si crystallization during interfacial reactions in thin Al/amorphous SiC layers

Interfacial reactions between thin films of Al and amorphous (a-) SiC annealed with tungsten-halogen lamps lead to the formation of Si fractal-like structures at temperatures as low as 275°C in less than 100 s. By using a-SiC/Al/a-SiC sandwiches with different SiC/Al thickness ratios, it is shown that the nucleation of Si crystals is faster on smaller-grained Al. This is attributed to the higher Al surface energy and the increased density of high-energy multiple grain junctions in thinner (smaller grained) Al layers. When the Al layer is very thin (≤50 Å) a solid-state amorphization reaction occurs between Al and a-SiC without subsequent Si crystallization. Formation of Al₄C₃ follows Si crystallization, or in the very thin Al layer, the amorphization reaction.