The structure of chalcogen pairs in silicon

The chalcogen pair centres (S-S) + and (Se-Se) + in Si were investigated with electron-nuclear double resonance (ENDOR). It was possible to resolve the superhyperfine interactions with 16 shells ((S-S) + ) and 20 shells ((Se-Se) + ) of 29 Si neighbours as well as with the central Se nuclei. From the analysis, it follows that in both cases the chalcogen atoms occupy substitutional lattice sites and are very slightly pulled to each other by bonding. The spin distributions of the monomer and dimer chalcogen centres are very similar and show largely a vacancy character.