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Photon Bunching in Cathodoluminescence

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We have measured the second order correlation function g(2)(t) of the cathodoluminescence intensity resulting from the excitation by fast electrons of defect centers in wide band-gap semiconductor nanocrystals of diamond and hexagonal boron nitride. We show that the cathodoluminescence second order correlation function g(2)(t) of multiple defect centers is dominated by a large, nanosecond zero-delay bunching (g(2)(0)>30), in stark contrast to their flat photoluminescence g(2)(t) function. We have developed a model showing that this bunching can be attributed to the synchronized emission from several defect centers excited by the same electron through the deexcitation of a bulk plasmon into few electron-hole pairs.

Recently published in S. Meuret et al Phys. Rev. Lett. 114 197401 (2015)

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Nanometric resolved luminescence in h-BN Flakes: excitons and stacking order

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Hexagonal boron nitride (h-BN) is one of the most promising candidates for light emitting devices in the far UV region, presenting a single strong excitonic emission at 5.8 eV. However, a single line appears only in extremely pure monocrystals that can hardly be obtained only though complex synthesis processes. Common h-BN samples present more complex emission spectra that have been generally attributed to the presence of structural defects. Despite a large number of experimental studies up to now it was not possible to attribute specific emission features to well identify defective structures. In this work we address this fundamental questions by adopting a theoretical and experimental approach combining few nanometer resolved cathodoluminescence techniques with high resolution transmission electron microscopy images and state of the art quantum mechanical simulations. Read more »

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