Sr. Boyd et al., INFRARED-ABSORPTION BY THE B-NITROGEN AGGREGATE IN DIAMOND, Philosophical magazine. B. Physics of condensed matter. Structural, electronic, optical and magnetic properties, 72(3), 1995, pp. 351-361
Two approaches have been adopted in attempting to determine the streng
th of the one-phonon infrared absorption by the B nitrogen aggregate i
n diamond. On the one hand, we have heat treated purely type IaA speci
mens with known infrared absorption strengths (and thus also known nit
rogen concentrations) to bring about partial aggregation of the A cent
res to B centres, monitoring changes in the strengths of the A, and re
sultant B, one-phonon components by decomposition of the ensuing infra
red spectra. Secondly, we have made direct chemical assays of nitrogen
in diamonds that show dominant B absorption features. This approach i
s complicated because diamonds in which the B aggregate is the only po
int defect also contain extended defects that may or may not involve n
itrogen. These defects may or may not, in turn, contribute to absorpti
on in the one-phonon region. Nevertheless, the nitrogen concentrations
have been measured for two distinct groups of diamonds that both uncr
itically might at first glance be typed together as 'IaB'. By taking i
nto account subtle differences between the infrared spectra of these g
roups, and making allowance for what is known from electron microscopi
cal observations about their defect contents, it is possible, despite
certain experimental indeterminacies, to arrive at a reasonably consis
tent interpretation of the measurements. A value of 794 +/- 8 at.ppm/c
m(-1) is suggested for the absorption strength, at 1282 wavenumbers, o
f the B nitrogen aggregate.