On the transformation of optically active defects in diamond crystal lattice

The energy activating aggregation of isolated substitutional nitrogen atoms (C centers) into nitrogen pairs (A centers) has been measured in synthetic diamonds which exhibit different absorption intensities in the 658.4 nm nickel defect (1.883 eV). It has been shown that if the intensity of this defect increases more than 10 times, the activation energy, on the contrary, decreases more than twice. A possible explanation of such dependence can be that nickel ions present in the 658.4 nm defect (1.883 eV) transform into some other more complex nickel defects on HPHT-annealing. The transformation of nickel defects is accompanied by the appearance of interstitials and vacancies that enhance the mobility of nitrogen atoms, thus making their aggregation to pairs easier. (C) 2003 Elsevier B.V. All rights reserved.