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Subwavelength optical characterization of colour centres in diamond using cathodoluminescence in a STEM

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In this work we report the spectrally and spatially resolved cathodoluminescence of diamond nanoparticles using in a scanning transmission electron microscope. Nanoparticles containing one or more neutral nitrogen-vacancy (NV0) intensity maxima have been characterized in detail. Based on the ensemble of data we attribute these maxima to individual emitters (L. H. G. Tizei and M. Kociak, Nanotechnology (2012))

Thanks to a spatial resolution which is solely limited by charge carrier diffusion in the case of a fast electron (80 keV) setup, the spectra of two individual NV0 emitters separated by 80 nm inside a nanoparticle have been spatially discerned. A shift of the zero phonon line (ZPL) between the two emitters, which we attribute to internal stress, is shown to arise even within the same nanoparticle. Detailed emission spectra (ZPL, phonon lines and Huang–Rhys factor, directly linked to the relaxation energy of the colour centre) in 51 individual NV0 centres have been measured in 39 particles. The ZPL and Huang–Rhys factor are found to be measurably dispersed, while the phonon energies keep constant.