Electron paramagnetic resonance studies of silicon-related defects in diamond

We report the results of multifrequency electron paramagnetic resonance studies at temperatures between 8 and 300 K on diamonds synthesized by chemical vapor deposition and intentionally silicon doped with isotopes in natural abundance or isotopically enriched. The S29i hyperfine structure has provided definitive evidence for the involvement of silicon in two electron paramagnetic resonance centers in diamond that were previously suspected to involve silicon: KUL1 and KUL3. We present data that unambiguously identify KUL1 as an S=1 neutral silicon split-vacancy ( D_3d symmetry) defect (V-Si-V)⁰ , while KUL3 is shown to be (V-Si-V)⁰ decorated with a hydrogen atom, (V-Si-V:H)⁰ .