Spectrally resolved confocal optical microscopic studies were made of spatially inhomogeneous colour centre distributions. These were generated by irradiation with a focussed beam of 400keV electrons, in a high-voltage transmission electron microscope, followed by annealing. Two centres, which had previously been attributed to the neutral and negatively charged N-vacancy complex, were found throughout the irradiation profile. A significant concentration enhancement of the neutral centre was found at positions which corresponded to large irradiation doses. In contrast to the case of neutron bombardment, no reduction in the concentration of negatively charged centres with increasing concentration of neutral centres was observed.

Confocal Microscopy of Color Center Distributions in Diamond. J.Martin, W.Grebner, W.Sigle, R.Wannemacher: Journal of Luminescence, 1999, 83-84, 493-7