Micron scale scanning imaging and diagnostics of natural and treated diamond with nitrogen-vacancy centers as a probe

Micron scale scanning imaging and diagnostics of diamonds of various origin using nitrogen-vacancy NV centers as a probe are presented. Natural plastically deformed crystals, natural cryptocrystalline aggregates (carbonado), treated crystal of type IIa, HPHT diamond bulk crystal and sintered compact were studied with photoluminescence (PL) and optically detected magnetic resonance (ODMR) spectroscopy based on a scanning confocal microscope.

NV⁻ centers carry information about the local properties of diamonds, such as the concentration of NV⁻ centers, their charge states, stresses and strains at the location of the NV⁻ center, the coherent properties of NV⁻ centers, and the interaction of these centers with donor nitrogen. The distribution of local stress and strain was obtained from the splitting of the ODMR line of NV⁻ centers in zero magnetic field. The average distance between NV⁻ center and nitrogen donors (P1 centers) and the local nitrogen concentration were estimated by ratio of satellite and central lines intensities in ODMR spectra in zero magnetic field, where the satellite lines are formed (in case of high concentrations of nitrogen donors) by the interaction of NV⁻ centers with single P1 centers and P1-P1 pairs. The magnetic field application causes an additional ODMR lines splitting which makes it possible to define the degree of mutual microcrystals orientation in cryptocrystalline aggregates. Information on the local distribution of the two NV center charge states, neutrally charged NV⁰ and negatively charged NV⁻ was obtained. The ratio of the NV center charge states is of fundamental interest for the applications of NV centers in sensorics and as an element base for quantum computing.

Confocal 3D scanning of PL- and ODMR-signals of NV centers allows us to reveal their space distribution within natural and treated diamonds and to obtain micron-scale images of internal structure.