NV- center in natural diamonds: Optically detected magnetic resonance study

The NV-/W15 centers (according to designations in optical/EPR spectroscopy) in natural diamonds were studied by means of optically detected magnetic resonance (ODMR). These centers are used to create quantum sensors and computer qubits, for which they are produced artificially by irradiation and subsequent annealing of crystals.The samples analyzed were plates cut of cubic habit crystals with increased single nitrogen C/P1 centers content from Anabar placers (Siberia). The parameters of their ODMR spectra were analyzed and compared with those of treated diamonds. Natural diamonds have a lower value, 4.8-7.9 MHz, of the 2E parameter of the NV- centers indicating the lower stress level in the crystals. We also found that the ODMR parameters noticeably vary over the volume of natural diamond crystals.Analyses of the ODMR spectra recorded with an applied magnetic field of 10 G suggest the preferential orientation of the NV- centers along only one of four (111) axes in the structure of natural diamonds studied.Confocal 2D scanning of the PL and ODMR signals with a submicron resolution were used to reveal the NV- centers spatial distribution in the crystals. We observed an increased concentration of the NV- centers within the slipping planes {111}, which argue that the formation of these centers in natural crystals studied occurred under postgrowth plastic deformation. In nature, diamonds suffered plastic deformation during the mantle rocks disintegration and subsequent transportation to the Earth surface.