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arXiv · 1806.11446

Cubic BN optical gap and intragap optically active defects

Anna Tararan·Stefano di Sabatino·Matteo Gatti·Takashi Taniguchi·Kenji Watanabe·Lucia Reining·Luiz H. G. Tizei·Mathieu Kociak·Alberto Zobelli
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Abstract

We report a comprehensive study on the optical properties of cubic boron nitride (c-BN) and its optically active defects. Using electron energy-loss spectroscopy (EELS) within a monochromated scanning transmission electron microscope (STEM) on the highest-quality crystals available, we demonstrate unequivocally that the optical-gap energy of c-BN slightly exceeds 10 eV. Further theoretical analysis in the framework of the Bethe-Salpeter equation of many-body perturbation theory supports this result. The spatial localization of defect-related emissions has been investigated using nanometric resolved cathodoluminescence (nano-CL) in a STEM. By high-temperature annealing a c-BN powder, we have promoted phase transitions in nanometric domains which have been detected by the appearance of specific hexagonal-phase signatures in both EELS and CL spectra. A high number of intragap optically active centers are known in c-BN, but the literature is rather scattered and hence has been summarized here. For several emission lines we have obtained nano-CL maps which show emission spot sizes as small as few tens of nanometers. Finally, by coupling nano-CL to a Hanbury-Brown-Twiss intensity interferometer, we have addressed individual spots in order to identify the possible presence of single-photon sources. The observed CL bunching effect is compatible with a limited set of single-photon emitters and it permits obtaining emission lifetimes of the order of the nanosecond.

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Anna Tararan, Stefano di Sabatino, Matteo Gatti, Takashi Taniguchi, Kenji Watanabe, Lucia Reining, Luiz H. G. Tizei, Mathieu Kociak, Alberto Zobelli. 2018-06-29. Cubic BN optical gap and intragap optically active defects. https://doi.org/10.1103/physrevb.98.094106

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