The use of luminescence and optical transmission topography revealed inhomogeneities in the distribution of N and Ni-related defects in synthetic diamonds that had been manufactured at high pressures. Due to the large supersaturations and temperature gradients which existed during growth, lighter areas (with higher contents of A-centers of pure N and complex Ni-N, NEl-NE3, defects) were present in yellow Ib samples. Coefficients were determined for NE1/NE2/NE3 concentrations and for the absorption strengths of the corresponding zero-phonon lines in the visual region. These centers were found to be stable during 3MeV electron irradiation and annealing at 1100K.

A.Yelisseyev, V.Nadolinny, B.Feigelson, S.Terentyev, S.Nosukhin: Diamond and Related Materials, 1996, 5[10], 1113-7