Numerical simulations and modeling of the stability of noble gas atoms in interaction with vacancies in silicon

In order to identify the main actors during the initial steps of the formation of noble gas filled bubbles, we have performed an extensive investigation of a single noble gas atom (helium, neon, argon, krypton, xenon) as interstitial or in interaction with a monovacancy and a divacancy in silicon. Density functional calculations in the generalized gradient approximation allowed us for determining the structure and stability of various configurations. We found that interstitial configurations are especially relevant for helium, and to a lesser extent for neon. Heavy noble gas species are predicted to form complexes with vacancies, except in out-of-equilibrium situations where an original bond-centered interstitial configuration is favored. Besides, we propose a model combining a repulsive interaction between the host local electronic density and the noble gas atom, and an elastic description of this atom as a deformable spherical inclusion into an homogeneous isotropic medium. This model is shown to provide an appropriate description, especially for light noble gas species such as helium and neon.