Wetting and crystallization at grain boundaries: Origin of aluminum-induced crystallization of amorphous silicon

It has been shown experimentally that the grain boundaries in aluminium in contact with amorphous silicon are the necessary agents for initiation of the crystallization of silicon upon annealing temperatures as low as 438K. Thermodynamic analysis has shown (i) that Si can “wet” the Al grain boundaries due to the favorable Si∕Al interface energy as compared to the Al grain-boundary energy and (ii) that Si at the Al grain boundaries can maintain its amorphous state up to a thickness of about 1.0nm. Beyond that thickness crystalline Si develops at the Al grain boundaries.