Electronic and dynamical properties of the silicon trivacancy

The trivacancy (V₃) in silicon has been recently shown to be a bistable center in the neutral charge state, with a fourfold-coordinated configuration, V₃[FFC], lower in energy than the $(110)$ planar one [V. P. Markevich et al., Phys. Rev. B 80, 235207 (2009)]. Transformations of the V₃ 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 V₃ transformation from the $(110)$ planar configuration to the fourfold-coordinated structure have been determined. The annealing studies demonstrate that V₃ is mobile in Si at $T>200$ ^∘C and in oxygen-rich material can be trapped by interstitial oxygen atoms so resulting in the appearance of V₃O complexes. The calculations suggest that V₃ motion takes place via consecutive FFC/planar transformation steps. The activation energy for the long-range diffusion of the V₃ center has been derived and agrees with atomic motion barrier from the calculations.