Formation of Silicon Nanoclusters in Disproportionation of Silicon Monoxide

The processes of the disproportionation of solid-phase silicon monoxide, accompanied by the formation of nanocrystalline silicon precipitates in the medium of amorphous suboxide SiOx (initial composition of SiO0.9), are studied. Based on the data of X-ray diffraction analysis and transmission electron microscopy, the dynamics of changes in the amount, concentration, and size of phase precipitates of silicon with the temperature of isochronous annealing increasing from 800 to 1200 degrees C is traced. It is found that, with the total mass of the precipitated silicon steadily increasing, the number of its crystallization centers per unit volume nonmonotonically depends on temperature. The activation energy of the diffusion of silicon atoms in the SiOx matrix is determined to be E-a1 = 1.64 eV and the activation energy of their transfer from precipitates formed to the SiOx growth medium is E-a2 = 2.38 eV. The anisotropic deformation of silicon crystallites precipitated during the disproportionation of SiO is revealed for the first time. This phenomenon is attributed to the difference between the specific volumes of the phases being separated and to the anisotropy of the growth rate of silicon precipitates formed in a solid amorphous medium.