Epitaxial upward transport of Al at the beginning of the Al-induced layer exchange process

Al-induced layer exchange (ALILE) and crystallization in a stack of amorphous Si (a-Si, 100 nm)/Al (50 nm)/quartz substrate, annealed at 450 °C, have been investigated at different length scales by optical microscopy as well as analytical scanning and transmission electron microscopy. Significant lateral and vertical redistribution of Al was observed, yielding Al deficient dendritic cell centers surrounded by an about 10 μm wide Al excess zone containing epitaxial islands of "pushed-up" Al whose number density and size decreases with increasing distance from the cell boundary. This new finding is likely to be a key step forward in the understanding of the complex redistribution of Al and Si during the ALILE process. (