Cluster-induced crystallization of nano-silicon particles

The possibility of producing from 20 nm to 100 nm sized silicon powders by plasma-induced reactions of silane including the formation of high-mass hydrogenated silicon anion clusters has been recently demonstrated. Careful HREM imaging showed circular contrast features, 1.5 to 2.5 nm in size, embedded in the amorphous particles which was attributed to the presence of medium range order in these regions. This nonhomogeneous atomic distribution with partially ordered regions of a couple of nanometer dimension became more pronounced upon annealing up to the onset of crystallization. This observation and the formation of fivefold crystallites thereafter indicate that the clusters serve as seeds in the amorphous-to-crystalline transition. (C) 1997 Acta Metallurgica Inc.