Theoretical Investigation of Luminescent Defects in Diamond

Abstract

The nitrogen-vacancy (NV) color center in diamond has attracted a lot of attention during the past few years. Its strong room temperature luminescence can be utilized in single photon emitters for quantum cryptography, and for optical labeling in biomedical imaging. All applications critically rely on thermodynamically and optically stable defects, introduced in sufficient concentration and suitable charge state. To clarify the conditions for that, I have performed theoretical calculations for bulk crystals, slabs and nanoclusters of diamond. I will show that the concentration of NV centers can be enhanced by increasing the irradiation flux and by using higher annealing temperatures, to annihilate divacancies. Most applications require NV(-) centers very close to the surface, which can affect the luminescence of the center, leading to undesired blinking effects or even bleaching. This also happens in nanodiamonds, where band- bending effects cannot be invoked for explanation. Therefore, I have investigated the interaction of surface states in variously terminated diamond slabs with the NV(-) center. I have identified a combination of surface terminators with no effect on the luminescence of this defect. Such a termination can be realized by mild oxidation of hydrogenated surfaces or by oxidation with acids.