Absorption and luminescence studies of synthetic diamond in which the nitrogen has been aggregated

Abstract

Absorption and cathodoluminescence spectra have been obtained from synthetic diamonds which have been heated at temperatures between 1700 and 2400 degrees C to produce various degrees of nitrogen aggregation. At the lower temperatures a number of optical centres attributed to nitrogen in intermediate stages of aggregation are observed; at the highest temperatures most of the nitrogen is present in the A-aggregate form with a small fraction in the B-aggregate form. The relative intensities of the Hib and Hic absorption lines in the near-infrared spectral region around 2 mu m provide a sensitive indication of the A- to B-nitrogen ratio. Although most of the nitrogen is present in aggregated form following these high-temperature treatments, the absorption and luminescence spectra are very different from those observed for natural type-Ia diamonds.