A new defect center in type Ib diamond inducing one phonon infrared absorption: The Y center

The infrared spectra of 68 natural and synthetic diamonds with detectable C centers at about 1130 cm− 1 and 1344 cm− 1 were recorded. After correction and normalization of the spectra there was an attempt to determine the A, B and C center nitrogen content of the samples using the spectral fitting spreadsheet supplied by David Fisher from the DTC. It became clear that for the majority of our samples the results were erroneous for the C center content. In fact, the calculated C center content based on the 1130 cm− 1 absorption was significantly higher than what the 1344 cm− 1 absorption height indicated; in the fitted traces proposed by the spreadsheet the 1344 cm− 1 absorption was always at least 50% higher than in the original spectrum. The overestimated C center content and the residual trace after spectral fitting indicated that some absorption bands were underlying the well-known, single-substitutional nitrogen absorption at 1130 cm− 1. For this reason all spectra were decomposed again by progressive subtraction of the A, B, C and X center absorptions, in order to visualize any residual absorption not attributed to any of those four, classically-recognized, nitrogen-related one-phonon absorption systems. In the spectra of 38 diamonds the decomposition work resulted in a consistent residual absorption feature with a relatively broad apparent maximum centered at about 1145 to 1150 cm− 1. For the sake of convenience we use “1145 cm− 1” to describe this feature. Two additional samples did not exhibit any 1130 cm− 1 absorption but instead precisely the same one-phonon absorption features as the newly-found residual. Consequently several hundred nominally type Ib diamonds were screened by infrared spectroscopy, and 22 had a one phonon absorption with a dominant 1145 cm− 1 absorption. This confirms that this absorption system was not an artifact of the original spectral decomposition work. Further, this new system is apparently a characteristic component of many natural type Ib diamonds.Based on the fact that this newly described center is clearly related to single substitutional nitrogen and that the last such one-phonon IR absorption had been named “X center” [1] (positively charged single nitrogen), we propose to call this defect “Y center”.

► Consistent new one-phonon component in C center containing diamonds is described: the Y center. ► Y center absorption can rarely be dominant but is frequently a component of C center containing diamonds. ► Correlation between Y center, X center and specific hydrogen absorptions is shown. ► The importance of this defect for nitrogen concentration determination is demonstrated.