Distribution of the cobalt-related luminescence center in HPHT diamond

We have studied photoluminescence and cathodoluminescence topography of annealed diamonds grown from cobalt. Yellow luminescence was confirmed to be restricted to (111) sectors and its intensity was higher in regions which grew at higher rates. The distribution of the luminescence was the same as that of nickel-related optical centers, indicating that the luminescence is produced by cobalt impurities because it is reasonably assumed that cobalt is trapped in the same manner as nickel. The result supports our previous report, which proposes a presence of cobalt impurities as optical centers. Two broad bands with peaks around 410 and 430 nm were observed in the annealed crystal. (C) 1997 Elsevier science S.A.