Photoluminescence Decomposition Analysis: A Technique to Characterize N-V Creation in Diamond

Abstract

Treatment of laboratory-grown diamond by electron irradiation and annealing has enabled quantum sensors based on negatively charged nitrogen-vacancy (N-V-) centers to demonstrate record sensitivities. Here we investigate the irradiation and annealing process applied to 28 diamond samples using an ambient-temperature, all-optical approach. As the presence of the neutrally charged nitrogen-vacancy (N-V0) center is deleterious to sensor performance, this photoluminescence decomposition analysis is first used to determine the concentration ratio of N-V- to N-V0 in diamond samples from the measured photoluminescence spectrum. The analysis hinges on (i) isolating each N-V charge state's emission spectrum and (ii) measuring the N-V- to N-V0 emission ratio, which is found to be 2.5±0.5 under low-intensity 532-nm illumination. Using the photoluminescence-decomposition-analysis method, we measure the effects of irradiation and annealing on conversion of substitutional nitrogen to N-V centers. Combining these measurements with a phenomenological model for diamond irradiation and annealing, we extract an estimated monovacancy creation rate of 0.52±0.26cm-1 for 1-MeV electron irradiation and an estimated monovacancy diffusion coefficient of 1.8 nm2/s at 850 C. Finally, we find that irradiation doses of 1018e-/cm2 or more deteriorate the N-V- decoherence time T2, whereas T1 is unaffected up to the the maximum investigated dose of 5×1018e-/cm2.