Structure of nanometersized silicon particles prepared by various gas phase processes

We have explored various gas phase processes for the fabrication of nanometersized Si and SiOx particles and measured their structural properties (agglomeration, size, shape, crystallinity, surface roughness and internal structure) by conventional and high resolution electron microscopy. Agglomerated amorphous Si particles, 10±30 nm in size, were prepared by gas phase reactions including cluster growth processes in a low pressure silane plasma. Annealing at 900°C resulted in almost complete crystallisation of nearly spherical particles covered by an amorphous oxide shell. Inert gas arc evaporation of silicon yielded single crystalline, spherical Si particles, 4±16 nm in size, in which no defects were detected. These particles, agglomerated into chains and tangles, are covered entirely by a thin amorphous oxide layer. Thermal evaporation of solid SiO in an inert gas atmosphere produced agglomerated, nearly spherical amorphous SiOx particles, 8±24 nm in size, with considerable surface roughness. Upon annealing at 900°C, the formation of 3±6 nm sized Si crystallites in the interior of these particles was observed. Ó 1998 Elsevier Science B.V. All rights reserved.