Magnetic resonance studies of point defects in single crystal diamond

Abstract

The results from EPR studies of CVD diamond which was intentionally silicon doped with isotopes in natural abundance or isotopically enriched are reported. The observation of hyperfine satellites arising due to the presence of 29Si has provided definitive evidence for the involvement of silicon in two EPR centres in diamond which were previously suspected to involve silicon: KUL1 and KUL3. KUL1 is unambiguously identified as the neutral silicon split vacancy defect (V-Si-V)0, whilst KUL3 is shown to be (V-Si-V)0 decorated with a hydrogen atom. Data have also revealed that (V-Si-V)0 is preferentially oriented in samples grown on {110} substrates. The negative nitrogen-vacancy centre (NV‑) has been investigated. Published parameters for the nitrogen hyperfine interaction produce an unsatisfactory fit to the experimental spectra and hence these parameters are redetermined. Optically-excited EPR has been used to estimate the degree of spin polarisation of the NV-ground state and the increase in signal intensity with illumination has permitted the interaction between the unpaired electron and neighbouring 13C atoms to be studied. Two sets of 13C hyperfine satellites have been identified, which account for ~100% of the unpaired electron probability density. Despite the predictions that the neutral charge state of NV should have an S = ½ ground state, this charge state has not previously been detected by EPR. Optically excited EPR measurements reveal a trigonal nitrogen containing defect in diamond with an excited state populated via optical excitation. Analysis of the spin-Hamiltonian parameters and the wavelength dependence of the optical excitation leads to assignment of this state to the 4A2 excited state of NV0