Cubic BN optical gap and intragap optically active defects

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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Cited by in corpus (7)

• Universal polarization energies for defects in monolayer, surface and bulk hexagonal boron nitride : A finite-size fragments GW approach
• Superbunching in cathodoluminescence: a master equation approach
• Quantum Confined Luminescence in Two dimensions
• Pressure Dependence of Electronic, Vibrational and Optical Properties of wurtzite-Boron Nitride
• An atlas of photonic and plasmonic materials for cathodoluminescence microscopy
• Optical spin defect pairs in cubic boron nitride
• Phonon assisted light absorption and emission in cubic-Boron Nitride