Electronic and dynamical properties of the silicon trivacancy

The trivacancy (V${}_3$) in silicon has been recently shown to be a bistable center in the neutral charge state, with a fourfold-coordinated configuration, V${}_3$[FFC], lower in energy than the $\left(110\right)$ planar one [V. P. Markevich et al., Phys. Rev. B 80, 235207 (2009)]. Transformations of the V${}_3$ defect between different configurations, its diffusion, and disappearance upon isochronal and isothermal annealing of electron-irradiated Si:O crystals are reported from joint deep level transient spectroscopy measurements and first-principles density-functional calculations. Activation energies and respective mechanisms for V${}_3$ transformation from the $\left(110\right)$ planar configuration to the fourfold-coordinated structure have been determined. The annealing studies demonstrate that V${}_3$ is mobile in Si at $T>200$ ${}^{\circ }$C and in oxygen-rich material can be trapped by interstitial oxygen atoms so resulting in the appearance of V${}_3$O complexes. The calculations suggest that V${}_3$ motion takes place via consecutive FFC/planar transformation steps. The activation energy for the long-range diffusion of the V${}_3$ center has been derived and agrees with atomic motion barrier from the calculations.