D. Fisher et Sc. Lawson, THE EFFECT OF NICKEL AND COBALT ON THE AGGREGATION OF NITROGEN IN DIAMOND, DIAMOND AND RELATED MATERIALS, 7(2-5), 1998, pp. 299-304
The effect of nickel and cobalt impurities on nitrogen aggregation in
high-pressure, high-temperature (HPHT)-grown synthetic diamonds has be
en investigated. Samples have been grown from solvent-catalysts of dif
ferent nickel-iron ratios to vary the nickel content. Experimentally,
a marking method has been developed to allow accurate repositioning of
samples for infra-red absorption measurements at each stage of the an
nealing, and samples have been carefully prepared to exclude the possi
bility of growth-sector overlap and to minimise effects due to inhomog
eneity within a growth-sector. The results indicate an enhancement in
{111} growth sectors due to the preferential incorporation of nickel,
with the degree of enhancement increasing with increasing nickel conte
nt. A marked deviation from simple second order kinetics was found for
the enhanced cases. Similar results were found for {111} sectors of c
obalt/iron-grown samples. Features in infra-red and visible absorption
spectra allow a model for the aggregation enhancement via interstitia
l atoms to be proposed. (C) 1998 Elsevier Science S.A.