Diamond crystal with Y-defects: spectroscopy and transmission electron microscopy
The paper presents results of investigation of a natural Ib-IaA diamond containing Y-defects from Yubileinaya kimberlite pipe, Yakutia. Analysis of spatial distribution of nitrogen-related A and C centers and intensity of Infra-red absorption at Raman frequency (1332 cm-1) reveals anticorrelation between these defects. Transmission electron microscopy of a zone with abundant Y-defects shows presence of dislocations in various configurations and numerous clusters of point defects generated by non-conservative dislocation motion. Extended defects with shape resembling thin (1-3 nm) rhombic plates with the largest dimension up to 20 nm are observed. Analysis of contrast of these defects shows that they represent nanosized voids (vacancy clusters). It is suggested that the defects were formed by annihilation of dislocation dipoles with subsequent growth by consumption of vacancies produced by non-conservative motion of dislocations. Upon excitation by 787 nm laser, numerous narrow photoluminescecne lines are observed between 800-900 nm; their intensity and position show pronounced spatial heterogeneity on scale of few microns. Qualitatively similar behaviour of photoluminescence was earlier noted for hydrogenated nanodiamonds. It is suggested that unusual behaviour of the luminescence lines may be explained by recombination processes at internal walls of the discovered nanovoids.