Elastic Instability of Strained Spherical Precipitates as a Cause of Oxide Platelets in Silicon

摘要

A strained spherical amorphous precipitate becomes unstable against transformation into a flat spheroid (platelet) when the combination P~2R of the precipitate radius, R, and the pressure inside the precipitate, P, exceeds a certain critical value. The kinetics of the transformation is analyzed for a small deviation of the precipitate shape from a sphere. The chemical potential of host atoms changes along the precipitate/matrix interface, due to a change in the curvature, the strain energy density and the specific volume of strained matrix. The corresponding diffusion fluxes of self-interstitials (outside the precipitate) and of extra host atoms (inside the precipitate) result in a shape evolution. For oxide particles in silicon, the self-interstitial diffusion is not enough to account for the sphere-to-platelet conversion. It is concluded that silicon transport through oxide is essential.