Localization of intrinsic defects in CaF2–BaF2 superlattices

Abstract

We perform first-principles calculations for the formation energies of fluorine self-interstitials (Fi−) and fluorine vacancies (VF+) in CaF2–BaF2 superlattices and in the corresponding bulk compounds. In dislocation-free (strained-layer) superlattices, the calculations show that both the Fi− and the VF+ defects are energetically more stable in the CaF2 layers than in the BaF2 layers. If the misfit stress in the superlattices is released (by dislocations, for instance), our results indicate that charge transfer between layers becomes energetically favorable with Fi− in the CaF2 layers and VF+ in the BaF2 layers. This is consistent with recent experiments.