Saddle point for oxygen reorientation in the vicinity of a silicon vacancy

A piezospectroscopic analysis of the vacancy-oxygen complex in silicon has enabled us to demonstrate that this defect in the unstable configuration of the saddle point on the reconfiguration trajectory has a trigonal symmetry. This unstable defect configuration may be considered as the precursor for an oxygen diffusion process where the migrating oxygen atom is accompanied by a vacancy. The trigonal saddle point configuration results in a strong electrical polarization of the pair which can aid the jumping to a neighboring unit cell. This scenario is very plausible to explain how vacancies can drag oxygen atoms through the crystal to form larger oxygen aggregates.